MyBatis原理（1）-启动流程3- mapper 加载

1.接着上一篇文章解析mapper第一步

 mapperElement(root.evalNode("mappers"));

 private void mapperElement(XNode parent) throws Exception {
    if (parent != null) {
      for (XNode child : parent.getChildren()) {
        if ("package".equals(child.getName())) {
          String mapperPackage = child.getStringAttribute("name");
          configuration.addMappers(mapperPackage);
        } else {
         //永远先执行else ，dtd文件中声明 <mappers>节点中的mapper节点必须在package节点前面
          String resource = child.getStringAttribute("resource");
          String url = child.getStringAttribute("url");
          String mapperClass = child.getStringAttribute("class");
          if (resource != null && url == null && mapperClass == null) {
           //只有resource属性
            ErrorContext.instance().resource(resource);
            InputStream inputStream = Resources.getResourceAsStream(resource);
            XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
            mapperParser.parse();
          } else if (resource == null && url != null && mapperClass == null) {
            ErrorContext.instance().resource(url);
            InputStream inputStream = Resources.getUrlAsStream(url);
            XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
            mapperParser.parse();
          } else if (resource == null && url == null && mapperClass != null) {
            Class<?> mapperInterface = Resources.classForName(mapperClass);
            configuration.addMapper(mapperInterface);
          } else {
            throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
          }
        }
      }
    }
  }

在这个过程中一共对应4种情况：
1）节点为package节点，则扫描这个包下所有mapper接口和对应注解，最后调用MapperRegistry的addMapper方法添加
2）节点为mapper节点分为三种情况
2-1）resource不为空从classpath加载
2-2）url不为空从URL加载
2-3）mapperClass不为空，调用Configuration的addMapper最后还是调用的MapperRegistry的addMapper，扫描接口和接口上的注解

上面四种可归结为2种方式：
1）使用mapper.xml生成代理类
2)使用接口和注解生成代理类
按加载的顺序先说以mapper.xml进行加载的方式：
2.构造XMLMapperBuilder

XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
            mapperParser.parse();

public class XMLMapperBuilder extends BaseBuilder {

  private final XPathParser parser;
  private final MapperBuilderAssistant builderAssistant;
  private final Map<String, XNode> sqlFragments;
  private final String resource;

  @Deprecated
  public XMLMapperBuilder(Reader reader, Configuration configuration, String resource, Map<String, XNode> sqlFragments, String namespace) {
    this(reader, configuration, resource, sqlFragments);
    this.builderAssistant.setCurrentNamespace(namespace);
  }

  @Deprecated
  public XMLMapperBuilder(Reader reader, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
    this(new XPathParser(reader, true, configuration.getVariables(), new XMLMapperEntityResolver()),
        configuration, resource, sqlFragments);
  }

  public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments, String namespace) {
    this(inputStream, configuration, resource, sqlFragments);
    this.builderAssistant.setCurrentNamespace(namespace);
  }

  public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
    this(new XPathParser(inputStream, true, configuration.getVariables(), new XMLMapperEntityResolver()),
        configuration, resource, sqlFragments);
  }

  private XMLMapperBuilder(XPathParser parser, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
   //初始化typeHandler 和typeRegistry
    super(configuration);
    this.builderAssistant = new MapperBuilderAssistant(configuration, resource);
    this.parser = parser;
    this.sqlFragments = sqlFragments;
    this.resource = resource;
  }

  public void parse() {
    if (!configuration.isResourceLoaded(resource)) {
      configurationElement(parser.evalNode("/mapper"));
     //添加到configruation中loadedResources，已经加载
      configuration.addLoadedResource(resource);
     //如果当前命名空间是接口的全限定名，为当前命名空间绑定相应的Mapper代理
      bindMapperForNamespace();
    }

    parsePendingResultMaps();
    parsePendingCacheRefs();
    parsePendingStatements();
  }

  public XNode getSqlFragment(String refid) {
    return sqlFragments.get(refid);
  }
  //加载mapper.xml中所有内容
  private void configurationElement(XNode context) {
    try {
      String namespace = context.getStringAttribute("namespace");
      if (namespace == null || namespace.equals("")) {
        throw new BuilderException("Mapper's namespace cannot be empty");
      }
      builderAssistant.setCurrentNamespace(namespace);
      cacheRefElement(context.evalNode("cache-ref"));
      cacheElement(context.evalNode("cache"));
      parameterMapElement(context.evalNodes("/mapper/parameterMap"));
      resultMapElements(context.evalNodes("/mapper/resultMap"));
      sqlElement(context.evalNodes("/mapper/sql"));
      buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
    } catch (Exception e) {
      throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
    }
  }

  private void buildStatementFromContext(List<XNode> list) {
    if (configuration.getDatabaseId() != null) {
      buildStatementFromContext(list, configuration.getDatabaseId());
    }
    buildStatementFromContext(list, null);
  }

  private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
    for (XNode context : list) {
      final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
      try {
        statementParser.parseStatementNode();
      } catch (IncompleteElementException e) {
        configuration.addIncompleteStatement(statementParser);
      }
    }
  }

  private void parsePendingResultMaps() {
    Collection<ResultMapResolver> incompleteResultMaps = configuration.getIncompleteResultMaps();
    synchronized (incompleteResultMaps) {
      Iterator<ResultMapResolver> iter = incompleteResultMaps.iterator();
      while (iter.hasNext()) {
        try {
          iter.next().resolve();
          iter.remove();
        } catch (IncompleteElementException e) {
          // ResultMap is still missing a resource...
        }
      }
    }
  }

  private void parsePendingCacheRefs() {
    Collection<CacheRefResolver> incompleteCacheRefs = configuration.getIncompleteCacheRefs();
    synchronized (incompleteCacheRefs) {
      Iterator<CacheRefResolver> iter = incompleteCacheRefs.iterator();
      while (iter.hasNext()) {
        try {
          iter.next().resolveCacheRef();
          iter.remove();
        } catch (IncompleteElementException e) {
          // Cache ref is still missing a resource...
        }
      }
    }
  }

  private void parsePendingStatements() {
    Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
    synchronized (incompleteStatements) {
      Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
      while (iter.hasNext()) {
        try {
          iter.next().parseStatementNode();
          iter.remove();
        } catch (IncompleteElementException e) {
          // Statement is still missing a resource...
        }
      }
    }
  }

  private void cacheRefElement(XNode context) {
    if (context != null) {
      configuration.addCacheRef(builderAssistant.getCurrentNamespace(), context.getStringAttribute("namespace"));
      CacheRefResolver cacheRefResolver = new CacheRefResolver(builderAssistant, context.getStringAttribute("namespace"));
      try {
        cacheRefResolver.resolveCacheRef();
      } catch (IncompleteElementException e) {
        configuration.addIncompleteCacheRef(cacheRefResolver);
      }
    }
  }

  private void cacheElement(XNode context) throws Exception {
    if (context != null) {
      String type = context.getStringAttribute("type", "PERPETUAL");
      Class<? extends Cache> typeClass = typeAliasRegistry.resolveAlias(type);
      String eviction = context.getStringAttribute("eviction", "LRU");
      Class<? extends Cache> evictionClass = typeAliasRegistry.resolveAlias(eviction);
      Long flushInterval = context.getLongAttribute("flushInterval");
      Integer size = context.getIntAttribute("size");
      boolean readWrite = !context.getBooleanAttribute("readOnly", false);
      boolean blocking = context.getBooleanAttribute("blocking", false);
      Properties props = context.getChildrenAsProperties();
      builderAssistant.useNewCache(typeClass, evictionClass, flushInterval, size, readWrite, blocking, props);
    }
  }

  private void parameterMapElement(List<XNode> list) throws Exception {
    for (XNode parameterMapNode : list) {
      String id = parameterMapNode.getStringAttribute("id");
      String type = parameterMapNode.getStringAttribute("type");
      Class<?> parameterClass = resolveClass(type);
      List<XNode> parameterNodes = parameterMapNode.evalNodes("parameter");
      List<ParameterMapping> parameterMappings = new ArrayList<ParameterMapping>();
      for (XNode parameterNode : parameterNodes) {
        String property = parameterNode.getStringAttribute("property");
        String javaType = parameterNode.getStringAttribute("javaType");
        String jdbcType = parameterNode.getStringAttribute("jdbcType");
        String resultMap = parameterNode.getStringAttribute("resultMap");
        String mode = parameterNode.getStringAttribute("mode");
        String typeHandler = parameterNode.getStringAttribute("typeHandler");
        Integer numericScale = parameterNode.getIntAttribute("numericScale");
        ParameterMode modeEnum = resolveParameterMode(mode);
        Class<?> javaTypeClass = resolveClass(javaType);
        JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
        @SuppressWarnings("unchecked")
        Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
        ParameterMapping parameterMapping = builderAssistant.buildParameterMapping(parameterClass, property, javaTypeClass, jdbcTypeEnum, resultMap, modeEnum, typeHandlerClass, numericScale);
        parameterMappings.add(parameterMapping);
      }
      builderAssistant.addParameterMap(id, parameterClass, parameterMappings);
    }
  }

  private void resultMapElements(List<XNode> list) throws Exception {
    for (XNode resultMapNode : list) {
      try {
        resultMapElement(resultMapNode);
      } catch (IncompleteElementException e) {
        // ignore, it will be retried
      }
    }
  }

  private ResultMap resultMapElement(XNode resultMapNode) throws Exception {
    return resultMapElement(resultMapNode, Collections.<ResultMapping> emptyList());
  }

  private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings) throws Exception {
    ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier());
    String id = resultMapNode.getStringAttribute("id",
        resultMapNode.getValueBasedIdentifier());
    String type = resultMapNode.getStringAttribute("type",
        resultMapNode.getStringAttribute("ofType",
            resultMapNode.getStringAttribute("resultType",
                resultMapNode.getStringAttribute("javaType"))));
    String extend = resultMapNode.getStringAttribute("extends");
    Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
    Class<?> typeClass = resolveClass(type);
    Discriminator discriminator = null;
    List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
    resultMappings.addAll(additionalResultMappings);
    List<XNode> resultChildren = resultMapNode.getChildren();
    for (XNode resultChild : resultChildren) {
      if ("constructor".equals(resultChild.getName())) {
        processConstructorElement(resultChild, typeClass, resultMappings);
      } else if ("discriminator".equals(resultChild.getName())) {
        discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
      } else {
        List<ResultFlag> flags = new ArrayList<ResultFlag>();
        if ("id".equals(resultChild.getName())) {
          flags.add(ResultFlag.ID);
        }
        resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
      }
    }
    ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping);
    try {
      return resultMapResolver.resolve();
    } catch (IncompleteElementException  e) {
      configuration.addIncompleteResultMap(resultMapResolver);
      throw e;
    }
  }

  private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
    List<XNode> argChildren = resultChild.getChildren();
    for (XNode argChild : argChildren) {
      List<ResultFlag> flags = new ArrayList<ResultFlag>();
      flags.add(ResultFlag.CONSTRUCTOR);
      if ("idArg".equals(argChild.getName())) {
        flags.add(ResultFlag.ID);
      }
      resultMappings.add(buildResultMappingFromContext(argChild, resultType, flags));
    }
  }

  private Discriminator processDiscriminatorElement(XNode context, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
    String column = context.getStringAttribute("column");
    String javaType = context.getStringAttribute("javaType");
    String jdbcType = context.getStringAttribute("jdbcType");
    String typeHandler = context.getStringAttribute("typeHandler");
    Class<?> javaTypeClass = resolveClass(javaType);
    @SuppressWarnings("unchecked")
    Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
    JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
    Map<String, String> discriminatorMap = new HashMap<String, String>();
    for (XNode caseChild : context.getChildren()) {
      String value = caseChild.getStringAttribute("value");
      String resultMap = caseChild.getStringAttribute("resultMap", processNestedResultMappings(caseChild, resultMappings));
      discriminatorMap.put(value, resultMap);
    }
    return builderAssistant.buildDiscriminator(resultType, column, javaTypeClass, jdbcTypeEnum, typeHandlerClass, discriminatorMap);
  }

  private void sqlElement(List<XNode> list) throws Exception {
    if (configuration.getDatabaseId() != null) {
      sqlElement(list, configuration.getDatabaseId());
    }
    sqlElement(list, null);
  }

  private void sqlElement(List<XNode> list, String requiredDatabaseId) throws Exception {
    for (XNode context : list) {
      String databaseId = context.getStringAttribute("databaseId");
      String id = context.getStringAttribute("id");
      id = builderAssistant.applyCurrentNamespace(id, false);
      if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
        sqlFragments.put(id, context);
      }
    }
  }
  
  private boolean databaseIdMatchesCurrent(String id, String databaseId, String requiredDatabaseId) {
    if (requiredDatabaseId != null) {
      if (!requiredDatabaseId.equals(databaseId)) {
        return false;
      }
    } else {
      if (databaseId != null) {
        return false;
      }
      // skip this fragment if there is a previous one with a not null databaseId
      if (this.sqlFragments.containsKey(id)) {
        XNode context = this.sqlFragments.get(id);
        if (context.getStringAttribute("databaseId") != null) {
          return false;
        }
      }
    }
    return true;
  }

  private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception {
    String property;
    if (flags.contains(ResultFlag.CONSTRUCTOR)) {
      property = context.getStringAttribute("name");
    } else {
      property = context.getStringAttribute("property");
    }
    String column = context.getStringAttribute("column");
    String javaType = context.getStringAttribute("javaType");
    String jdbcType = context.getStringAttribute("jdbcType");
    String nestedSelect = context.getStringAttribute("select");
    String nestedResultMap = context.getStringAttribute("resultMap",
        processNestedResultMappings(context, Collections.<ResultMapping> emptyList()));
    String notNullColumn = context.getStringAttribute("notNullColumn");
    String columnPrefix = context.getStringAttribute("columnPrefix");
    String typeHandler = context.getStringAttribute("typeHandler");
    String resultSet = context.getStringAttribute("resultSet");
    String foreignColumn = context.getStringAttribute("foreignColumn");
    boolean lazy = "lazy".equals(context.getStringAttribute("fetchType", configuration.isLazyLoadingEnabled() ? "lazy" : "eager"));
    Class<?> javaTypeClass = resolveClass(javaType);
    @SuppressWarnings("unchecked")
    Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
    JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
    return builderAssistant.buildResultMapping(resultType, property, column, javaTypeClass, jdbcTypeEnum, nestedSelect, nestedResultMap, notNullColumn, columnPrefix, typeHandlerClass, flags, resultSet, foreignColumn, lazy);
  }
  
  private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
    if ("association".equals(context.getName())
        || "collection".equals(context.getName())
        || "case".equals(context.getName())) {
      if (context.getStringAttribute("select") == null) {
        ResultMap resultMap = resultMapElement(context, resultMappings);
        return resultMap.getId();
      }
    }
    return null;
  }

  private void bindMapperForNamespace() {
    String namespace = builderAssistant.getCurrentNamespace();
    if (namespace != null) {
      Class<?> boundType = null;
      try {
        boundType = Resources.classForName(namespace);
      } catch (ClassNotFoundException e) {
        //ignore, bound type is not required
      }
      if (boundType != null) {
        if (!configuration.hasMapper(boundType)) {
          // Spring may not know the real resource name so we set a flag
          // to prevent loading again this resource from the mapper interface
          // look at MapperAnnotationBuilder#loadXmlResource
          configuration.addLoadedResource("namespace:" + namespace);
          configuration.addMapper(boundType);
        }
      }
    }
  }

}

XMLMapperBuilder也继承自BaseBuilder,和XMLConfigBuilder 不同的是XMLMapperBuilder是解析mapperXMLConfigBuilder解析config，很显然XMLMapperBuilder也必须有一个XpathParser对象负责解析mapper，同样也需要一个XMLMapperEntityResolver。XMLMapperBuilder构造参数中传入的

configuration.getSqlFragments()

在Configuration中

  protected final Map<String, XNode> sqlFragments = new StrictMap<XNode>("XML fragments parsed from previous mappers");

存放了所有的已经加载的sql语句。XMLMapperBuilder中包含一个MapperBuilderAssistant成员变量
保存了当前mapper文件的命名空间、缓存等信息。
总结一下：XMLMapperBuilder是mapper包含mapper文件所有的信息,缓存信息、命名空间存放在MapperBuilderAssistant，解析器和所有sql语句集合的引用。
3.  mapperParser.parse()

public void parse() {
    if (!configuration.isResourceLoaded(resource)) {
      configurationElement(parser.evalNode("/mapper"));
      configuration.addLoadedResource(resource);
      bindMapperForNamespace();
    }

    parsePendingResultMaps();
    parsePendingCacheRefs();
    parsePendingStatements();
  }

3.1  配置mapper

configurationElement(parser.evalNode("/mapper"));

private void configurationElement(XNode context) {
    try {
      String namespace = context.getStringAttribute("namespace");
      if (namespace == null || namespace.equals("")) {
        throw new BuilderException("Mapper's namespace cannot be empty");
      }
      builderAssistant.setCurrentNamespace(namespace);
      cacheRefElement(context.evalNode("cache-ref"));
      cacheElement(context.evalNode("cache"));
      parameterMapElement(context.evalNodes("/mapper/parameterMap"));
      resultMapElements(context.evalNodes("/mapper/resultMap"));
      sqlElement(context.evalNodes("/mapper/sql"));
      buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
    } catch (Exception e) {
      throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
    }
  }

首先会调用cacheRefElement方法检测是否有引用的缓存(二级缓存)如果有引用的缓存存在，检测应用缓存是否已经加载，已经加载：将引用缓存设置为当前缓存，否则将引用的缓存放入configuration中的

  protected final Collection<CacheRefResolver> incompleteCacheRefs = new LinkedList<CacheRefResolver>();

相关方法如下：

 private void cacheRefElement(XNode context) {
    if (context != null) {
      configuration.addCacheRef(builderAssistant.getCurrentNamespace(), context.getStringAttribute("namespace"));
      CacheRefResolver cacheRefResolver = new CacheRefResolver(builderAssistant, context.getStringAttribute("namespace"));
      try {
        cacheRefResolver.resolveCacheRef();
      } catch (IncompleteElementException e) {
        configuration.addIncompleteCacheRef(cacheRefResolver);
      }
    }
  }
//CacheRefResolver#resolveCacheRef
public Cache resolveCacheRef() {
    return assistant.useCacheRef(cacheRefNamespace);
  }
//#MapperBuilderAssistant#useCacheRef
public Cache useCacheRef(String namespace) {
    if (namespace == null) {
      throw new BuilderException("cache-ref element requires a namespace attribute.");
    }
    try {
      unresolvedCacheRef = true;
      Cache cache = configuration.getCache(namespace);
      if (cache == null) {
        throw new IncompleteElementException("No cache for namespace '" + namespace + "' could be found.");
      }
      currentCache = cache;
      unresolvedCacheRef = false;
      return cache;
    } catch (IllegalArgumentException e) {
     /不存在/strictMap直接抛出异常
      throw new IncompleteElementException("No cache for namespace '" + namespace + "' could be found.", e);
    }
  }

3.2    检测<cache节点>

 cacheElement(context.evalNode("cache"));

首先获取节点属性type，是否自定义缓存，如果没有默认为PERPETUAL即PerpetualCache缓存，这个类已经注册在Configuration中typeAliasRegistry中在调用Configuration的初始化方法的时候，下面继续获取缓存各个属性最后调用MapperBuilderAssistant.useNewCache设置当前currentCache中并同时加入Configuration的

 protected final Map<String, Cache> caches = new StrictMap<Cache>("Caches collection");

 public Cache useNewCache(Class<? extends Cache> typeClass,
      Class<? extends Cache> evictionClass,
      Long flushInterval,
      Integer size,
      boolean readWrite,
      boolean blocking,
      Properties props) {
    Cache cache = new CacheBuilder(currentNamespace)
        .implementation(valueOrDefault(typeClass, PerpetualCache.class))
        .addDecorator(valueOrDefault(evictionClass, LruCache.class))
        .clearInterval(flushInterval)
        .size(size)
        .readWrite(readWrite)
        .blocking(blocking)
        .properties(props)
        .build();
    configuration.addCache(cache);
    currentCache = cache;
    return cache;
  }

//TODO myabtis Cache分析
3.3 parameterMap解析已经废弃使用不在分析
3.4 resultMap 解析
resultMap的解析流程如下：
resultMapElement方法循环的遍历下面每个子节点并封装成ResultMapping，并构造ResultMapResolver最后调用MapperBuilderAssistant的resolve方法，resolve调用MapperBuilderAssistant的addResultMap方法，addResultMap设置当前命名空间并去掉extend的构造函数的ResultMapping，ResultMap并调用ResultMap的build方法设置并验证requestMppings的属性转换为自身属性，最后生产ResultMap，并将其注入到Configuration中。
在解析ResultMap之前需要先看下ResultMapping这个类，ResultMap是myabtis映射强大的原因，resultMap解析这部分有点复杂，ResultMapping简单来说就是resultMap和其下面所有节点的抽象，其他节点只是在上面增加了其他属性，标识是constructor还是id，是否有children节点（复合节点）等，所以ResultMapping对应ResultMap节点下的每一行。下面一步一步的进行解析。

public class ResultMapping {

  private Configuration configuration;
  //每个节点的property属性对应domain中的实体属性
  private String property;
//database 中的列
  private String column;
//当前列的java类型
  private Class<?> javaType;
//当前列的jdbc类型
  private JdbcType jdbcType;
//对应的类型处理器
  private TypeHandler<?> typeHandler;
//嵌套的resultMap的id
  private String nestedResultMapId;
//嵌套的nestedQueryId
  private String nestedQueryId;
//不为空的列
  private Set<String> notNullColumns;
//列前缀
  private String columnPrefix;
//标注当前是construtor还是id
  private List<ResultFlag> flags;
//复合主键详见MapperBuilderAssistant#parseCompositeColumnName解析复合主键
  private List<ResultMapping> composites;
  private String resultSet;
  private String foreignColumn;
//懒加载
  private boolean lazy;

  ResultMapping() {
  }

  public static class Builder {
    private ResultMapping resultMapping = new ResultMapping();

    public Builder(Configuration configuration, String property, String column, TypeHandler<?> typeHandler) {
      this(configuration, property);
      resultMapping.column = column;
      resultMapping.typeHandler = typeHandler;
    }

    public Builder(Configuration configuration, String property, String column, Class<?> javaType) {
      this(configuration, property);
      resultMapping.column = column;
      resultMapping.javaType = javaType;
    }

    public Builder(Configuration configuration, String property) {
      resultMapping.configuration = configuration;
      resultMapping.property = property;
      resultMapping.flags = new ArrayList<ResultFlag>();
      resultMapping.composites = new ArrayList<ResultMapping>();
      resultMapping.lazy = configuration.isLazyLoadingEnabled();
    }

    public Builder javaType(Class<?> javaType) {
      resultMapping.javaType = javaType;
      return this;
    }

    public Builder jdbcType(JdbcType jdbcType) {
      resultMapping.jdbcType = jdbcType;
      return this;
    }

    public Builder nestedResultMapId(String nestedResultMapId) {
      resultMapping.nestedResultMapId = nestedResultMapId;
      return this;
    }

    public Builder nestedQueryId(String nestedQueryId) {
      resultMapping.nestedQueryId = nestedQueryId;
      return this;
    }

    public Builder resultSet(String resultSet) {
      resultMapping.resultSet = resultSet;
      return this;
    }

    public Builder foreignColumn(String foreignColumn) {
      resultMapping.foreignColumn = foreignColumn;
      return this;
    }

    public Builder notNullColumns(Set<String> notNullColumns) {
      resultMapping.notNullColumns = notNullColumns;
      return this;
    }

    public Builder columnPrefix(String columnPrefix) {
      resultMapping.columnPrefix = columnPrefix;
      return this;
    }

    public Builder flags(List<ResultFlag> flags) {
      resultMapping.flags = flags;
      return this;
    }

    public Builder typeHandler(TypeHandler<?> typeHandler) {
      resultMapping.typeHandler = typeHandler;
      return this;
    }

    public Builder composites(List<ResultMapping> composites) {
      resultMapping.composites = composites;
      return this;
    }

    public Builder lazy(boolean lazy) {
      resultMapping.lazy = lazy;
      return this;
    }
    
    public ResultMapping build() {
      // lock down collections
      resultMapping.flags = Collections.unmodifiableList(resultMapping.flags);
      resultMapping.composites = Collections.unmodifiableList(resultMapping.composites);
      resolveTypeHandler();
      validate();
      return resultMapping;
    }

    private void validate() {
      // Issue #697: cannot define both nestedQueryId and nestedResultMapId
      if (resultMapping.nestedQueryId != null && resultMapping.nestedResultMapId != null) {
        throw new IllegalStateException("Cannot define both nestedQueryId and nestedResultMapId in property " + resultMapping.property);
      }
      // Issue #5: there should be no mappings without typehandler
      if (resultMapping.nestedQueryId == null && resultMapping.nestedResultMapId == null && resultMapping.typeHandler == null) {
        throw new IllegalStateException("No typehandler found for property " + resultMapping.property);
      }
      // Issue #4 and GH #39: column is optional only in nested resultmaps but not in the rest
      if (resultMapping.nestedResultMapId == null && resultMapping.column == null && resultMapping.composites.isEmpty()) {
        throw new IllegalStateException("Mapping is missing column attribute for property " + resultMapping.property);
      }
      if (resultMapping.getResultSet() != null) {
        int numColumns = 0;
        if (resultMapping.column != null) {
          numColumns = resultMapping.column.split(",").length;
        }
        int numForeignColumns = 0;
        if (resultMapping.foreignColumn != null) {
          numForeignColumns = resultMapping.foreignColumn.split(",").length;
        }
        if (numColumns != numForeignColumns) {
          throw new IllegalStateException("There should be the same number of columns and foreignColumns in property " + resultMapping.property);
        }
      }
    }
    
    private void resolveTypeHandler() {
      if (resultMapping.typeHandler == null && resultMapping.javaType != null) {
        Configuration configuration = resultMapping.configuration;
        TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
        resultMapping.typeHandler = typeHandlerRegistry.getTypeHandler(resultMapping.javaType, resultMapping.jdbcType);
      }
    }

    public Builder column(String column) {
      resultMapping.column = column;
      return this;
    }
  }

  public String getProperty() {
    return property;
  }

  public String getColumn() {
    return column;
  }

  public Class<?> getJavaType() {
    return javaType;
  }

  public JdbcType getJdbcType() {
    return jdbcType;
  }

  public TypeHandler<?> getTypeHandler() {
    return typeHandler;
  }

  public String getNestedResultMapId() {
    return nestedResultMapId;
  }

  public String getNestedQueryId() {
    return nestedQueryId;
  }

  public Set<String> getNotNullColumns() {
    return notNullColumns;
  }

  public String getColumnPrefix() {
    return columnPrefix;
  }

  public List<ResultFlag> getFlags() {
    return flags;
  }

  public List<ResultMapping> getComposites() {
    return composites;
  }

  public boolean isCompositeResult() {
    return this.composites != null && !this.composites.isEmpty();
  }

  public String getResultSet() {
    return this.resultSet;
  }

  public String getForeignColumn() {
    return foreignColumn;
  }

  public void setForeignColumn(String foreignColumn) {
    this.foreignColumn = foreignColumn;
  }

  public boolean isLazy() {
    return lazy;
  }

  public void setLazy(boolean lazy) {
    this.lazy = lazy;
  }
  
  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    ResultMapping that = (ResultMapping) o;

    if (property == null || !property.equals(that.property)) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    if (property != null) {
      return property.hashCode();
    } else if (column != null) {
      return column.hashCode();
    } else {
      return 0;
    }
  }

  @Override
  public String toString() {
    final StringBuilder sb = new StringBuilder("ResultMapping{");
    //sb.append("configuration=").append(configuration); // configuration doesn't have a useful .toString()
    sb.append("property='").append(property).append('\'');
    sb.append(", column='").append(column).append('\'');
    sb.append(", javaType=").append(javaType);
    sb.append(", jdbcType=").append(jdbcType);
    //sb.append(", typeHandler=").append(typeHandler); // typeHandler also doesn't have a useful .toString()
    sb.append(", nestedResultMapId='").append(nestedResultMapId).append('\'');
    sb.append(", nestedQueryId='").append(nestedQueryId).append('\'');
    sb.append(", notNullColumns=").append(notNullColumns);
    sb.append(", columnPrefix='").append(columnPrefix).append('\'');
    sb.append(", flags=").append(flags);
    sb.append(", composites=").append(composites);
    sb.append(", resultSet='").append(resultSet).append('\'');
    sb.append(", foreignColumn='").append(foreignColumn).append('\'');
    sb.append(", lazy=").append(lazy);
    sb.append('}');
    return sb.toString();
  }

}

ResultMap才是真正的对应的<ResultMap>节点

public class ResultMap {
  private Configuration configuration;
  //当前ResultMap的id，当前命名空间的id+语句的id
  private String id;
 //当前ResultMap的type
  private Class<?> type;
 //<result>节点
  private List<ResultMapping> resultMappings;
//复合主键
  private List<ResultMapping> idResultMappings;
//构造函数
  private List<ResultMapping> constructorResultMappings;
//
  private List<ResultMapping> propertyResultMappings;
//所有映射的列
  private Set<String> mappedColumns;
//映射的属性
  private Set<String> mappedProperties;
//鉴别器
  private Discriminator discriminator;
//是否有嵌套的ResultMap
  private boolean hasNestedResultMaps;
//是否有嵌套的select语句
  private boolean hasNestedQueries;
//是否是自动映射
  private Boolean autoMapping;

  private ResultMap() {
  }

  public static class Builder {
    private static final Log log = LogFactory.getLog(Builder.class);

    private ResultMap resultMap = new ResultMap();

    public Builder(Configuration configuration, String id, Class<?> type, List<ResultMapping> resultMappings) {
      this(configuration, id, type, resultMappings, null);
    }

    public Builder(Configuration configuration, String id, Class<?> type, List<ResultMapping> resultMappings, Boolean autoMapping) {
      resultMap.configuration = configuration;
      resultMap.id = id;
      resultMap.type = type;
      resultMap.resultMappings = resultMappings;
      resultMap.autoMapping = autoMapping;
    }

    public Builder discriminator(Discriminator discriminator) {
      resultMap.discriminator = discriminator;
      return this;
    }

    public Class<?> type() {
      return resultMap.type;
    }

    public ResultMap build() {
      if (resultMap.id == null) {
        throw new IllegalArgumentException("ResultMaps must have an id");
      }
      resultMap.mappedColumns = new HashSet<String>();
      resultMap.mappedProperties = new HashSet<String>();
      resultMap.idResultMappings = new ArrayList<ResultMapping>();
      resultMap.constructorResultMappings = new ArrayList<ResultMapping>();
      resultMap.propertyResultMappings = new ArrayList<ResultMapping>();
      final List<String> constructorArgNames = new ArrayList<String>();
      for (ResultMapping resultMapping : resultMap.resultMappings) {
        resultMap.hasNestedQueries = resultMap.hasNestedQueries || resultMapping.getNestedQueryId() != null;
        resultMap.hasNestedResultMaps = resultMap.hasNestedResultMaps || (resultMapping.getNestedResultMapId() != null && resultMapping.getResultSet() == null);
        final String column = resultMapping.getColumn();
        if (column != null) {
          resultMap.mappedColumns.add(column.toUpperCase(Locale.ENGLISH));
        } else if (resultMapping.isCompositeResult()) {
          for (ResultMapping compositeResultMapping : resultMapping.getComposites()) {
            final String compositeColumn = compositeResultMapping.getColumn();
            if (compositeColumn != null) {
              resultMap.mappedColumns.add(compositeColumn.toUpperCase(Locale.ENGLISH));
            }
          }
        }
        final String property = resultMapping.getProperty();
        if(property != null) {
          resultMap.mappedProperties.add(property);
        }
        if (resultMapping.getFlags().contains(ResultFlag.CONSTRUCTOR)) {
          resultMap.constructorResultMappings.add(resultMapping);
          if (resultMapping.getProperty() != null) {
            constructorArgNames.add(resultMapping.getProperty());
          }
        } else {
          resultMap.propertyResultMappings.add(resultMapping);
        }
        if (resultMapping.getFlags().contains(ResultFlag.ID)) {
          resultMap.idResultMappings.add(resultMapping);
        }
      }
      if (resultMap.idResultMappings.isEmpty()) {
        resultMap.idResultMappings.addAll(resultMap.resultMappings);
      }
      if (!constructorArgNames.isEmpty()) {
        final List<String> actualArgNames = argNamesOfMatchingConstructor(constructorArgNames);
        if (actualArgNames == null) {
          throw new BuilderException("Error in result map '" + resultMap.id
              + "'. Failed to find a constructor in '"
              + resultMap.getType().getName() + "' by arg names " + constructorArgNames
              + ". There might be more info in debug log.");
        }
        Collections.sort(resultMap.constructorResultMappings, new Comparator<ResultMapping>() {
          @Override
          public int compare(ResultMapping o1, ResultMapping o2) {
            int paramIdx1 = actualArgNames.indexOf(o1.getProperty());
            int paramIdx2 = actualArgNames.indexOf(o2.getProperty());
            return paramIdx1 - paramIdx2;
          }
        });
      }
      // lock down collections
      resultMap.resultMappings = Collections.unmodifiableList(resultMap.resultMappings);
      resultMap.idResultMappings = Collections.unmodifiableList(resultMap.idResultMappings);
      resultMap.constructorResultMappings = Collections.unmodifiableList(resultMap.constructorResultMappings);
      resultMap.propertyResultMappings = Collections.unmodifiableList(resultMap.propertyResultMappings);
      resultMap.mappedColumns = Collections.unmodifiableSet(resultMap.mappedColumns);
      return resultMap;
    }

    private List<String> argNamesOfMatchingConstructor(List<String> constructorArgNames) {
      Constructor<?>[] constructors = resultMap.type.getDeclaredConstructors();
      for (Constructor<?> constructor : constructors) {
        Class<?>[] paramTypes = constructor.getParameterTypes();
        if (constructorArgNames.size() == paramTypes.length) {
          List<String> paramNames = getArgNames(constructor);
          if (constructorArgNames.containsAll(paramNames)
              && argTypesMatch(constructorArgNames, paramTypes, paramNames)) {
            return paramNames;
          }
        }
      }
      return null;
    }

    private boolean argTypesMatch(final List<String> constructorArgNames,
        Class<?>[] paramTypes, List<String> paramNames) {
      for (int i = 0; i < constructorArgNames.size(); i++) {
        Class<?> actualType = paramTypes[paramNames.indexOf(constructorArgNames.get(i))];
        Class<?> specifiedType = resultMap.constructorResultMappings.get(i).getJavaType();
        if (!actualType.equals(specifiedType)) {
          if (log.isDebugEnabled()) {
            log.debug("While building result map '" + resultMap.id
                + "', found a constructor with arg names " + constructorArgNames
                + ", but the type of '" + constructorArgNames.get(i)
                + "' did not match. Specified: [" + specifiedType.getName() + "] Declared: ["
                + actualType.getName() + "]");
          }
          return false;
        }
      }
      return true;
    }

    private List<String> getArgNames(Constructor<?> constructor) {
      List<String> paramNames = new ArrayList<String>();
      List<String> actualParamNames = null;
      final Annotation[][] paramAnnotations = constructor.getParameterAnnotations();
      int paramCount = paramAnnotations.length;
      for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
        String name = null;
        for (Annotation annotation : paramAnnotations[paramIndex]) {
          if (annotation instanceof Param) {
            name = ((Param) annotation).value();
            break;
          }
        }
        if (name == null && resultMap.configuration.isUseActualParamName() && Jdk.parameterExists) {
          if (actualParamNames == null) {
            actualParamNames = ParamNameUtil.getParamNames(constructor);
          }
          if (actualParamNames.size() > paramIndex) {
            name = actualParamNames.get(paramIndex);
          }
        }
        paramNames.add(name != null ? name : "arg" + paramIndex);
      }
      return paramNames;
    }
  }

  public String getId() {
    return id;
  }

  public boolean hasNestedResultMaps() {
    return hasNestedResultMaps;
  }

  public boolean hasNestedQueries() {
    return hasNestedQueries;
  }

  public Class<?> getType() {
    return type;
  }

  public List<ResultMapping> getResultMappings() {
    return resultMappings;
  }

  public List<ResultMapping> getConstructorResultMappings() {
    return constructorResultMappings;
  }

  public List<ResultMapping> getPropertyResultMappings() {
    return propertyResultMappings;
  }

  public List<ResultMapping> getIdResultMappings() {
    return idResultMappings;
  }

  public Set<String> getMappedColumns() {
    return mappedColumns;
  }

  public Set<String> getMappedProperties() {
    return mappedProperties;
  }

  public Discriminator getDiscriminator() {
    return discriminator;
  }

  public void forceNestedResultMaps() {
    hasNestedResultMaps = true;
  }
  
  public Boolean getAutoMapping() {
    return autoMapping;
  }

}

      resultMapElements(context.evalNodes("/mapper/resultMap"));

resultMapElements方法解析每个Result节点

 private void resultMapElements(List<XNode> list) throws Exception {
    for (XNode resultMapNode : list) {
      try {
        resultMapElement(resultMapNode);
      } catch (IncompleteElementException e) {
        // ignore, it will be retried
      }
    }
  }

前面提到过ResultMapping表示ResultMap中的每一行，解析的时候不难考虑需要初始化一个空集合来保存所有的行

 private ResultMap resultMapElement(XNode resultMapNode) throws Exception {
    
    return resultMapElement(resultMapNode, Collections.<ResultMapping> emptyList());
  }


  private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings) throws Exception {
   //初始化日志
  //getValueBasedIdentifier 获取默认节点名称 
    ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier());
   //获取resultMap节点id属性
    String id = resultMapNode.getStringAttribute("id",
        resultMapNode.getValueBasedIdentifier());
    //这里不仅仅是获取type类型，因为每一行都是resultMaping自身和其子节点的抽象
  //所以当前方法可以解析每个节点对应的属性，这些属性直接必须是互斥的，即type只能在resultMap根节点不能再Collection上，而collection上只能有ofType不能有type属性
//后面会看到processNestedResultMappings会调用resultMapElement解析嵌套节点
    String type = resultMapNode.getStringAttribute("type",
        resultMapNode.getStringAttribute("ofType",
            resultMapNode.getStringAttribute("resultType",
                resultMapNode.getStringAttribute("javaType"))));
    //如果不是ResultMap根节点 extend=null
    String extend = resultMapNode.getStringAttribute("extends");
    //ResultMap节点本身属性解析完成
    //当前节点是ResultMap根节点或者collection或者association节点，其他节点为null
    Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
   //加载当前类型
    Class<?> typeClass = resolveClass(type);
    Discriminator discriminator = null;
    //ResultMapping 封装了 整个resultMap的属性、嵌套关系等
    List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
   //TODO
    resultMappings.addAll(additionalResultMappings);
    List<XNode> resultChildren = resultMapNode.getChildren();
   //依次解析ResultMap节点下的 constructor。discriminator
    for (XNode resultChild : resultChildren) {
      if ("constructor".equals(resultChild.getName())) {
       //解析constructor
        processConstructorElement(resultChild, typeClass, resultMappings);
      } else if ("discriminator".equals(resultChild.getName())) {
       //解析discriminator
        discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
      } else {
        List<ResultFlag> flags = new ArrayList<ResultFlag>();
        if ("id".equals(resultChild.getName())) {
          flags.add(ResultFlag.ID);
        }
        resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
      }
    }
    ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping);
    try {
      return resultMapResolver.resolve();
    } catch (IncompleteElementException  e) {
      configuration.addIncompleteResultMap(resultMapResolver);
      throw e;
    }
  }

   解析Constructor节点,很简单只是简单的把是否是ResultFlag.CONSTRUCTOR标识添加进去

  private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
    List<XNode> argChildren = resultChild.getChildren();
    for (XNode argChild : argChildren) {
      List<ResultFlag> flags = new ArrayList<ResultFlag>();
      flags.add(ResultFlag.CONSTRUCTOR);
      if ("idArg".equals(argChild.getName())) {
        flags.add(ResultFlag.ID);
      }
      resultMappings.add(buildResultMappingFromContext(argChild, resultType, flags));
    }
  }

很多地方都调用了buildResultMappingFromContext

private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception {
    String property;
   //如果是constructor子节点（前面设置了标志），property代表的是构造函数的名称
    if (flags.contains(ResultFlag.CONSTRUCTOR)) {
      property = context.getStringAttribute("name");
    } else {
      property = context.getStringAttribute("property");
    }
    String column = context.getStringAttribute("column");
    String javaType = context.getStringAttribute("javaType");
    String jdbcType = context.getStringAttribute("jdbcType");
    //嵌套的sql语句的id 
    String nestedSelect = context.getStringAttribute("select");
   //嵌套的resultMap
    String nestedResultMap = context.getStringAttribute("resultMap",
    //如果存在resultMap解析嵌套的resultMap，
        processNestedResultMappings(context, Collections.<ResultMapping> emptyList()));
  //notNullColumn 只在这些列不为空时才创建映射对象
    String notNullColumn = context.getStringAttribute("notNullColumn");
   //将匹配sql别名中的前缀
    String columnPrefix = context.getStringAttribute("columnPrefix");
  
    String typeHandler = context.getStringAttribute("typeHandler");
   //TODO
    String resultSet = context.getStringAttribute("resultSet");
  //TODO
    String foreignColumn = context.getStringAttribute("foreignColumn");
  //是否懒加载，这里的配置优先于myabtis-config.xml配置的
    boolean lazy = "lazy".equals(context.getStringAttribute("fetchType", configuration.isLazyLoadingEnabled() ? "lazy" : "eager"));
    Class<?> javaTypeClass = resolveClass(javaType);
    @SuppressWarnings("unchecked")
    Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
    JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
    return builderAssistant.buildResultMapping(resultType, property, column, javaTypeClass, jdbcTypeEnum, nestedSelect, nestedResultMap, notNullColumn, columnPrefix, typeHandlerClass, flags, resultSet, foreignColumn, lazy);
  }

processNestedResultMappings会对当前节点继续调用resultMapElement，一成一层的解析

  private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
    if ("association".equals(context.getName())
        || "collection".equals(context.getName())
        || "case".equals(context.getName())) {
      if (context.getStringAttribute("select") == null) {
        ResultMap resultMap = resultMapElement(context, resultMappings);
        return resultMap.getId();
      }
    }
    return null;
  }

继续 builderAssistant.buildResultMapping
第一个参数是：

 String type = resultMapNode.getStringAttribute("type",
        resultMapNode.getStringAttribute("ofType",
            resultMapNode.getStringAttribute("resultType",
                resultMapNode.getStringAttribute("javaType"))));

 public ResultMapping buildResultMapping(
      Class<?> resultType,
      String property,
      String column,
      Class<?> javaType,
      JdbcType jdbcType,
      String nestedSelect,
      String nestedResultMap,
      String notNullColumn,
      String columnPrefix,
      Class<? extends TypeHandler<?>> typeHandler,
      List<ResultFlag> flags,
      String resultSet,
      String foreignColumn,
      boolean lazy) {
    Class<?> javaTypeClass = resolveResultJavaType(resultType, property, javaType);
    TypeHandler<?> typeHandlerInstance = resolveTypeHandler(javaTypeClass, typeHandler);
    List<ResultMapping> composites = parseCompositeColumnName(column);
    return new ResultMapping.Builder(configuration, property, column, javaTypeClass)
        .jdbcType(jdbcType)
        .nestedQueryId(applyCurrentNamespace(nestedSelect, true))
        .nestedResultMapId(applyCurrentNamespace(nestedResultMap, true))
        .resultSet(resultSet)
        .typeHandler(typeHandlerInstance)
        .flags(flags == null ? new ArrayList<ResultFlag>() : flags)
        .composites(composites)
        .notNullColumns(parseMultipleColumnNames(notNullColumn))
        .columnPrefix(columnPrefix)
        .foreignColumn(foreignColumn)
        .lazy(lazy)
        .build();
  }

继续解析Discriminator

  private Discriminator processDiscriminatorElement(XNode context, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
    String column = context.getStringAttribute("column");
    String javaType = context.getStringAttribute("javaType");
    String jdbcType = context.getStringAttribute("jdbcType");
    String typeHandler = context.getStringAttribute("typeHandler");
    Class<?> javaTypeClass = resolveClass(javaType);
    @SuppressWarnings("unchecked")
    Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
    JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
    Map<String, String> discriminatorMap = new HashMap<String, String>();
    for (XNode caseChild : context.getChildren()) {
      String value = caseChild.getStringAttribute("value");
      String resultMap = caseChild.getStringAttribute("resultMap", processNestedResultMappings(caseChild, resultMappings));
      discriminatorMap.put(value, resultMap);
    }
    return builderAssistant.buildDiscriminator(resultType, column, javaTypeClass, jdbcTypeEnum, typeHandlerClass, discriminatorMap);
  }

值得注意的是在ResultMapping中如过遇到extend属性，且extend对应的resultMap还未装载则addResultMap抛出IncompleteElementException异常，由入口resultMapElement进行捕获，最后添加到configuation中的incompleteResultMaps中。在下一步都解析完成的时候在进行parsePendingResultMaps即对incompleteResultMaps进行清理，重新resolve。


总结一下：整个resultMapElements的过程在这个过程中涉及到的方法、类有
1）resultMaping:对应resultMapping中的每一行,这样做的好处就是可以支持递归，将整个ResultMap节点视为一棵树，constructor，discriminator，id，property，column等其他属性作为整棵树的属性值，composites存放复合主键
2）ResultMap：才是真正的ResultMap节点，包含了ResultMap的各个属性节点，ResultMap和resultMaping的关系是一对多
3)MapperBuilderAssistant:负责构建requestMapping和RequestMap，设置命名空间等。
4）XMLMapperBuilder：跟其他继承自BaseBuilder的类一样，负责整个ResultMap节点的解析工作，同时组合其他组件一起协调，整个解析ResultMap的原理大概分为三部：
1.递归的生成requestMapping
2.将requestMapping添加到List中
3.处理集合生成RequesMap
跟常见递归的处理方式差不多

解析sql节点

      sqlElement(context.evalNodes("/mapper/sql"));

由以下三个方法完成

private void sqlElement(List<XNode> list) throws Exception {
   //首先判断当前已经加载的database的id
    if (configuration.getDatabaseId() != null) {
    //加载当前数据库对应sql
      sqlElement(list, configuration.getDatabaseId());
    }
   //然后再加载默认的sql
    sqlElement(list, null);
  }

  private void sqlElement(List<XNode> list, String requiredDatabaseId) throws Exception {
    for (XNode context : list) {
      String databaseId = context.getStringAttribute("databaseId");
      String id = context.getStringAttribute("id");
      id = builderAssistant.applyCurrentNamespace(id, false);
  
      if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
        sqlFragments.put(id, context);
      }
    }
  }
  /**
   2种情况：只加载attribute获取databaseid为空的和Configuration中已经加载的数据源匹配的，还会判断是否有相同id的已经加载，已经加载当前节点则忽略
  
  **/
  private boolean databaseIdMatchesCurrent(String id, String databaseId, String requiredDatabaseId) {
    if (requiredDatabaseId != null) {
      if (!requiredDatabaseId.equals(databaseId)) {
        return false;
      }
    } else {
      if (databaseId != null) {
        return false;
      }
      // skip this fragment if there is a previous one with a not null databaseId
      if (this.sqlFragments.containsKey(id)) {
        XNode context = this.sqlFragments.get(id);
        if (context.getStringAttribute("databaseId") != null) {
          return false;
        }
      }
    }
    return true;
  }

加载 真正的SQL语句insert update select delete

      buildStatementFromContext(context.evalNodes("select|insert|update|delete"));

 private void buildStatementFromContext(List<XNode> list) {
    if (configuration.getDatabaseId() != null) {
      buildStatementFromContext(list, configuration.getDatabaseId());
    }
    buildStatementFromContext(list, null);
  }

这里又引入了一个XMLStatementBuilder，同样也继承自BaseBuilder，负责解析sql

  private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
    for (XNode context : list) {
      final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
      try {
        statementParser.parseStatementNode();
      } catch (IncompleteElementException e) {
        configuration.addIncompleteStatement(statementParser);
      }
    }
  }

XMLStatementBuilder

/**

public class XMLStatementBuilder extends BaseBuilder {

  private final MapperBuilderAssistant builderAssistant;
  private final XNode context;
  private final String requiredDatabaseId;

  public XMLStatementBuilder(Configuration configuration, MapperBuilderAssistant builderAssistant, XNode context) {
    this(configuration, builderAssistant, context, null);
  }

  public XMLStatementBuilder(Configuration configuration, MapperBuilderAssistant builderAssistant, XNode context, String databaseId) {
    super(configuration);
    this.builderAssistant = builderAssistant;
    this.context = context;
    this.requiredDatabaseId = databaseId;
  }

  public void parseStatementNode() {
    String id = context.getStringAttribute("id");
    String databaseId = context.getStringAttribute("databaseId");

    if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
      return;
    }

    Integer fetchSize = context.getIntAttribute("fetchSize");
    Integer timeout = context.getIntAttribute("timeout");
    String parameterMap = context.getStringAttribute("parameterMap");
    String parameterType = context.getStringAttribute("parameterType");
    Class<?> parameterTypeClass = resolveClass(parameterType);
    String resultMap = context.getStringAttribute("resultMap");
    String resultType = context.getStringAttribute("resultType");
    String lang = context.getStringAttribute("lang");
    LanguageDriver langDriver = getLanguageDriver(lang);

    Class<?> resultTypeClass = resolveClass(resultType);
    String resultSetType = context.getStringAttribute("resultSetType");
    StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
    ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);

    String nodeName = context.getNode().getNodeName();
    SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
   //不是select语句都刷新缓存
    boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
  //select语句使用缓存
    boolean useCache = context.getBooleanAttribute("useCache", isSelect);
    boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);

    // Include Fragments before parsing
    XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
    includeParser.applyIncludes(context.getNode());

    // Parse selectKey after includes and remove them.
    processSelectKeyNodes(id, parameterTypeClass, langDriver);
    
    // Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
    SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
    String resultSets = context.getStringAttribute("resultSets");
    String keyProperty = context.getStringAttribute("keyProperty");
    String keyColumn = context.getStringAttribute("keyColumn");
    KeyGenerator keyGenerator;
    String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
    keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
    if (configuration.hasKeyGenerator(keyStatementId)) {
      keyGenerator = configuration.getKeyGenerator(keyStatementId);
    } else {
      keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
          configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
          ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
    }

    builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
        fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
        resultSetTypeEnum, flushCache, useCache, resultOrdered, 
        keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
  }

  private void processSelectKeyNodes(String id, Class<?> parameterTypeClass, LanguageDriver langDriver) {
    List<XNode> selectKeyNodes = context.evalNodes("selectKey");
    if (configuration.getDatabaseId() != null) {
      parseSelectKeyNodes(id, selectKeyNodes, parameterTypeClass, langDriver, configuration.getDatabaseId());
    }
    parseSelectKeyNodes(id, selectKeyNodes, parameterTypeClass, langDriver, null);
    removeSelectKeyNodes(selectKeyNodes);
  }

  private void parseSelectKeyNodes(String parentId, List<XNode> list, Class<?> parameterTypeClass, LanguageDriver langDriver, String skRequiredDatabaseId) {
    for (XNode nodeToHandle : list) {
      String id = parentId + SelectKeyGenerator.SELECT_KEY_SUFFIX;
      String databaseId = nodeToHandle.getStringAttribute("databaseId");
      if (databaseIdMatchesCurrent(id, databaseId, skRequiredDatabaseId)) {
        parseSelectKeyNode(id, nodeToHandle, parameterTypeClass, langDriver, databaseId);
      }
    }
  }

  private void parseSelectKeyNode(String id, XNode nodeToHandle, Class<?> parameterTypeClass, LanguageDriver langDriver, String databaseId) {
    String resultType = nodeToHandle.getStringAttribute("resultType");
    Class<?> resultTypeClass = resolveClass(resultType);
    StatementType statementType = StatementType.valueOf(nodeToHandle.getStringAttribute("statementType", StatementType.PREPARED.toString()));
    String keyProperty = nodeToHandle.getStringAttribute("keyProperty");
    String keyColumn = nodeToHandle.getStringAttribute("keyColumn");
    boolean executeBefore = "BEFORE".equals(nodeToHandle.getStringAttribute("order", "AFTER"));

    //defaults
    boolean useCache = false;
    boolean resultOrdered = false;
    KeyGenerator keyGenerator = NoKeyGenerator.INSTANCE;
    Integer fetchSize = null;
    Integer timeout = null;
    boolean flushCache = false;
    String parameterMap = null;
    String resultMap = null;
    ResultSetType resultSetTypeEnum = null;

    SqlSource sqlSource = langDriver.createSqlSource(configuration, nodeToHandle, parameterTypeClass);
    SqlCommandType sqlCommandType = SqlCommandType.SELECT;

    builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
        fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
        resultSetTypeEnum, flushCache, useCache, resultOrdered,
        keyGenerator, keyProperty, keyColumn, databaseId, langDriver, null);

    id = builderAssistant.applyCurrentNamespace(id, false);

    MappedStatement keyStatement = configuration.getMappedStatement(id, false);
    configuration.addKeyGenerator(id, new SelectKeyGenerator(keyStatement, executeBefore));
  }

  private void removeSelectKeyNodes(List<XNode> selectKeyNodes) {
    for (XNode nodeToHandle : selectKeyNodes) {
      nodeToHandle.getParent().getNode().removeChild(nodeToHandle.getNode());
    }
  }

  private boolean databaseIdMatchesCurrent(String id, String databaseId, String requiredDatabaseId) {
    if (requiredDatabaseId != null) {
      if (!requiredDatabaseId.equals(databaseId)) {
        return false;
      }
    } else {
      if (databaseId != null) {
        return false;
      }
      // skip this statement if there is a previous one with a not null databaseId
      id = builderAssistant.applyCurrentNamespace(id, false);
      if (this.configuration.hasStatement(id, false)) {
        MappedStatement previous = this.configuration.getMappedStatement(id, false); // issue #2
        if (previous.getDatabaseId() != null) {
          return false;
        }
      }
    }
    return true;
  }

  private LanguageDriver getLanguageDriver(String lang) {
    Class<?> langClass = null;
    if (lang != null) {
      langClass = resolveClass(lang);
    }
    return builderAssistant.getLanguageDriver(langClass);
  }

}

解析<include>

public class XMLIncludeTransformer {

  private final Configuration configuration;
  private final MapperBuilderAssistant builderAssistant;

  public XMLIncludeTransformer(Configuration configuration, MapperBuilderAssistant builderAssistant) {
    this.configuration = configuration;
    this.builderAssistant = builderAssistant;
  }

  public void applyIncludes(Node source) {
    Properties variablesContext = new Properties();
    Properties configurationVariables = configuration.getVariables();
    if (configurationVariables != null) {
      variablesContext.putAll(configurationVariables);
    }
    applyIncludes(source, variablesContext, false);
  }

  /**递归的包含所有include相关的sql
   * Recursively apply includes through all SQL fragments.
   * @param source Include node in DOM tree
   * @param variablesContext Current context for static variables with values
   */
  private void applyIncludes(Node source, final Properties variablesContext, boolean included) {
    if (source.getNodeName().equals("include")) {
      Node toInclude = findSqlFragment(getStringAttribute(source, "refid"), variablesContext);
      Properties toIncludeContext = getVariablesContext(source, variablesContext);
      //上面两句都是为解析sql片段中的表达式，并赋值
    //如果<sql>标签节点下面还有include标签递归的赋值下去
      applyIncludes(toInclude, toIncludeContext, true);
      //当前被include的文档对象和当前文档对象不相等（不是同一个xml）直接用原来dom对象import include中的内容，并且递归的include下去
      if (toInclude.getOwnerDocument() != source.getOwnerDocument()) {
        toInclude = source.getOwnerDocument().importNode(toInclude, true);
      }
     // include的上一级节点用已经解析后的新的替换掉
      source.getParentNode().replaceChild(toInclude, source);
     //替换掉后用sql中的内容替换掉<include>标签，就是插入，再删除的过程
    //每次删除第一个include标签，就完成了整个<sql>节点将include节点替换的过程
    //无论当前sql节点或者insert,update等节点有多少节点都可以
      while (toInclude.hasChildNodes()) {
        //
        toInclude.getParentNode().insertBefore(toInclude.getFirstChild(), toInclude);
      }
      toInclude.getParentNode().removeChild(toInclude);
     //如果当前节点不是include节点是where test 等其他节点，同样递归的进行值替换
    } else if (source.getNodeType() == Node.ELEMENT_NODE) {
      if (included && !variablesContext.isEmpty()) {
        // replace variables in attribute values
        NamedNodeMap attributes = source.getAttributes();
        for (int i = 0; i < attributes.getLength(); i++) {
          Node attr = attributes.item(i);
          attr.setNodeValue(PropertyParser.parse(attr.getNodeValue(), variablesContext));
        }
      }
      NodeList children = source.getChildNodes();
      for (int i = 0; i < children.getLength(); i++) {
        applyIncludes(children.item(i), variablesContext, included);
      }
     //这里是整个递归的结束点 ，替换文本编写的SQL语句中的存在的表达式
    } else if (included && source.getNodeType() == Node.TEXT_NODE
        && !variablesContext.isEmpty()) {
      // replace variables in text node
      source.setNodeValue(PropertyParser.parse(source.getNodeValue(), variablesContext));
    }
  }

  private Node findSqlFragment(String refid, Properties variables) {
    //用configuration中的variables填充refid中的${}
    refid = PropertyParser.parse(refid, variables);
    //设置当前引用的语句id为 当前命名空间+refid
    refid = builderAssistant.applyCurrentNamespace(refid, true);
    try {
     //从之前解析出的sql片段中获取
      XNode nodeToInclude = configuration.getSqlFragments().get(refid);
       //返回当前节点的副本
      return nodeToInclude.getNode().cloneNode(true);
    } catch (IllegalArgumentException e) {
      throw new IncompleteElementException("Could not find SQL statement to include with refid '" + refid + "'", e);
    }
  }

  private String getStringAttribute(Node node, String name) {
    return node.getAttributes().getNamedItem(name).getNodeValue();
  }

  /**
   * Read placeholders and their values from include node definition. 
   * @param node Include node instance
   * @param inheritedVariablesContext Current context used for replace variables in new variables values
   * @return variables context from include instance (no inherited values)
   */
  //获取当前configuration中的Variables 加上include语句中的property子句中设置的name和value值
  private Properties getVariablesContext(Node node, Properties inheritedVariablesContext) {
    Map<String, String> declaredProperties = null;
    NodeList children = node.getChildNodes();
    for (int i = 0; i < children.getLength(); i++) {
      Node n = children.item(i);
      if (n.getNodeType() == Node.ELEMENT_NODE) {
        String name = getStringAttribute(n, "name");
        // Replace variables inside
        String value = PropertyParser.parse(getStringAttribute(n, "value"), inheritedVariablesContext);
        if (declaredProperties == null) {
          declaredProperties = new HashMap<String, String>();
        }
        if (declaredProperties.put(name, value) != null) {
          throw new BuilderException("Variable " + name + " defined twice in the same include definition");
        }
      }
    }
    if (declaredProperties == null) {
      return inheritedVariablesContext;
    } else {
      Properties newProperties = new Properties();
      newProperties.putAll(inheritedVariablesContext);
      newProperties.putAll(declaredProperties);
      return newProperties;
    }
  }
}

//TODO回头在写Selectkey

解析我们编写的真正的sql

    SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);

@Override
  public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) {
    XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
    return builder.parseScriptNode();
  }

XMLScriptBuilder又是一个BaseBuilder的子类
私有属性：

private final XNode context;
  private boolean isDynamic;
  private final Class<?> parameterType;
  private final Map<String, NodeHandler> nodeHandlerMap = new HashMap<String, NodeHandler>();

XMLScriptBuilder处理的是整个SQL语句，NodeHandler则是对应每个内部标签的处理器
NodeHandler  是XMLScriptBuilder的一个私有接口，先介绍下相关的一些类：

NodeHander 负责生成对应的sqlNode

private interface NodeHandler {
    void handleNode(XNode nodeToHandle, List<SqlNode> targetContents);
  }

所有实现类

SqlNode

public interface SqlNode {
  boolean apply(DynamicContext context);
}

所有实现类：
[img]
http://my.iteye.com/admin/picture/138343
[/img]
SqlSource

public interface SqlSource {

  BoundSql getBoundSql(Object parameterObject);

}

http://my.iteye.com/admin/picture/138345

BoundSql:

public class BoundSql {

  private final String sql;
  private final List<ParameterMapping> parameterMappings;
  private final Object parameterObject;
  private final Map<String, Object> additionalParameters;
  private final MetaObject metaParameters;

  public BoundSql(Configuration configuration, String sql, List<ParameterMapping> parameterMappings, Object parameterObject) {
    this.sql = sql;
    this.parameterMappings = parameterMappings;
    this.parameterObject = parameterObject;
    this.additionalParameters = new HashMap<String, Object>();
    this.metaParameters = configuration.newMetaObject(additionalParameters);
  }

  public String getSql() {
    return sql;
  }

  public List<ParameterMapping> getParameterMappings() {
    return parameterMappings;
  }

  public Object getParameterObject() {
    return parameterObject;
  }

  public boolean hasAdditionalParameter(String name) {
    String paramName = new PropertyTokenizer(name).getName();
    return additionalParameters.containsKey(paramName);
  }

  public void setAdditionalParameter(String name, Object value) {
    metaParameters.setValue(name, value);
  }

  public Object getAdditionalParameter(String name) {
    return metaParameters.getValue(name);
  }
}

ParameterMapping :

public class ParameterMapping {

  private Configuration configuration;

  private String property;
  private ParameterMode mode;
  private Class<?> javaType = Object.class;
  private JdbcType jdbcType;
  private Integer numericScale;
  private TypeHandler<?> typeHandler;
  private String resultMapId;
  private String jdbcTypeName;
  private String expression;

  private ParameterMapping() {
  }

MetaObject:

public class MetaObject {

  private final Object originalObject;
  private final ObjectWrapper objectWrapper;
  private final ObjectFactory objectFactory;
  private final ObjectWrapperFactory objectWrapperFactory;
  private final ReflectorFactory reflectorFactory;

回到XMLLanguageDriver,createSqlSource中创建XMLScriptBuilder，构造方法初始化
XMLScriptBuilder的nodeHandlerMap即为每个语句都注册了这么多节点处理器。

 public XMLScriptBuilder(Configuration configuration, XNode context) {
    this(configuration, context, null);
  }

  public XMLScriptBuilder(Configuration configuration, XNode context, Class<?> parameterType) {
    super(configuration);
    this.context = context;
    this.parameterType = parameterType;
    initNodeHandlerMap();
  }


  private void initNodeHandlerMap() {
    nodeHandlerMap.put("trim", new TrimHandler());
    nodeHandlerMap.put("where", new WhereHandler());
    nodeHandlerMap.put("set", new SetHandler());
    nodeHandlerMap.put("foreach", new ForEachHandler());
    nodeHandlerMap.put("if", new IfHandler());
    nodeHandlerMap.put("choose", new ChooseHandler());
    nodeHandlerMap.put("when", new IfHandler());
    nodeHandlerMap.put("otherwise", new OtherwiseHandler());
    nodeHandlerMap.put("bind", new BindHandler());
  }

继续执行parseScriptNode方法

  public SqlSource parseScriptNode() {
    MixedSqlNode rootSqlNode = parseDynamicTags(context);
    SqlSource sqlSource = null;
    if (isDynamic) {
      sqlSource = new DynamicSqlSource(configuration, rootSqlNode);
    } else {
      sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType);
    }
    return sqlSource;
  }

//动态和静态文本sql同在
public class MixedSqlNode implements SqlNode {
  private final List<SqlNode> contents;

  public MixedSqlNode(List<SqlNode> contents) {
    this.contents = contents;
  }

  @Override
  public boolean apply(DynamicContext context) {
    for (SqlNode sqlNode : contents) {
      sqlNode.apply(context);
    }
    return true;
  }
}

解析动态sql ：动态sql的定义是，包含${}的文本节点和包含其他标签(if trim where 等)

protected MixedSqlNode parseDynamicTags(XNode node) {
    List<SqlNode> contents = new ArrayList<SqlNode>();
    NodeList children = node.getNode().getChildNodes();
    for (int i = 0; i < children.getLength(); i++) {//值得注意的是如果当前node中包含换行的空行时也会被当做文本节点最后加入到contents，所有应该去掉无所谓的空行
      XNode child = node.newXNode(children.item(i));
     //如果节点是CDATA或者文本节点
      if (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {
        String data = child.getStringBody("");
        TextSqlNode textSqlNode = new TextSqlNode(data);
       //解析文本标签是否包含${},是则为动态语句,否则不是通过GenericTokenParser回调DynamicCheckerTokenParser设置textSqlNode的isDynamic属性
        if (textSqlNode.isDynamic()) {
          contents.add(textSqlNode);
          isDynamic = true;
        } else {
          contents.add(new StaticTextSqlNode(data));
        }
      //如果获取的标签是 Node 节点
      } else if (child.getNode().getNodeType() == Node.ELEMENT_NODE) { // issue #628
        String nodeName = child.getNode().getNodeName();
       //直接调用处理器，未找到相应处理器则抛出异常
        NodeHandler handler = nodeHandlerMap.get(nodeName);
        if (handler == null) {
          throw new BuilderException("Unknown element <" + nodeName + "> in SQL statement.");
        }
        handler.handleNode(child, contents);
        isDynamic = true;
      }
    }
    return new MixedSqlNode(contents);
  }

查看NodeHandler的实现类,handleNode方法都是将<tag>相应属性进行解析后放在，然后新增一个与handler类型相对应的SqlNode实现类并放入targetContents中，每次循环当前<insert>< select><update>节点都会解析标签体内的动态标签，最终生成一个包含所有静态、动态、文本标签的SqlNode---MixedSqlNode：

  private final List<SqlNode> contents;

  public MixedSqlNode(List<SqlNode> contents) {
    this.contents = contents;
  }

  @Override
  public boolean apply(DynamicContext context) {
    for (SqlNode sqlNode : contents) {
      sqlNode.apply(context);
    }
    return true;
  }
}

到此sql解析的第一步已经完成，生成中间产物MixedSqlNode，继续执行生成-DynamicSqlSource：

      sqlSource = new DynamicSqlSource(configuration, rootSqlNode);

public class DynamicSqlSource implements SqlSource {

  private final Configuration configuration;
  private final SqlNode rootSqlNode;

  public DynamicSqlSource(Configuration configuration, SqlNode rootSqlNode) {
    this.configuration = configuration;
    this.rootSqlNode = rootSqlNode;
  }

  @Override
  public BoundSql getBoundSql(Object parameterObject) {
    DynamicContext context = new DynamicContext(configuration, parameterObject);
    rootSqlNode.apply(context);
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
    SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
    BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
    for (Map.Entry<String, Object> entry : context.getBindings().entrySet()) {
      boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
    }
    return boundSql;
  }

}

获取相关属性后执行MapperBuilderAssistant#addMappedStatement

  public MappedStatement addMappedStatement(
      String id,
      SqlSource sqlSource,
      StatementType statementType,
      SqlCommandType sqlCommandType,
      Integer fetchSize,
      Integer timeout,
      String parameterMap,
      Class<?> parameterType,
      String resultMap,
      Class<?> resultType,
      ResultSetType resultSetType,
      boolean flushCache,
      boolean useCache,
      boolean resultOrdered,
      KeyGenerator keyGenerator,
      String keyProperty,
      String keyColumn,
      String databaseId,
      LanguageDriver lang,
      String resultSets) {

    if (unresolvedCacheRef) {
      //在解析      cacheRefElement(context.evalNode("cache-ref")) cache-ref的时候
      //如果当前缓存未被加载unresolvedCacheRef=true，这时会抛出异常，被XMLMapperBuilder#buildStatementFromContext捕获执行
//configuration.addIncompleteStatement(statementParser);
//最后在XMLMapperBuilder#parse方法最后依次执行
// parsePendingResultMaps();
  //  parsePendingCacheRefs();
   // parsePendingStatements();
//其中parsePendingStatements会再次调用parseStatementNode方法执行addMappedStatement
      throw new IncompleteElementException("Cache-ref not yet resolved");
    }
  //TODO
    id = applyCurrentNamespace(id, false);
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;

    MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType)
        .resource(resource)
        .fetchSize(fetchSize)
        .timeout(timeout)
        .statementType(statementType)
        .keyGenerator(keyGenerator)
        .keyProperty(keyProperty)
        .keyColumn(keyColumn)
        .databaseId(databaseId)
        .lang(lang)
        .resultOrdered(resultOrdered)
        .resultSets(resultSets)
        .resultMaps(getStatementResultMaps(resultMap, resultType, id))
        .resultSetType(resultSetType)
        .flushCacheRequired(valueOrDefault(flushCache, !isSelect))
        .useCache(valueOrDefault(useCache, isSelect))
        .cache(currentCache);

    ParameterMap statementParameterMap = getStatementParameterMap(parameterMap, parameterType, id);
    if (statementParameterMap != null) {
      statementBuilder.parameterMap(statementParameterMap);
    }

    MappedStatement statement = statementBuilder.build();
    configuration.addMappedStatement(statement);
    return statement;
  }

mapper.xml解析完之后回到XMLMapperBuilder的parse方法：

     configuration.addLoadedResource(resource);
      bindMapperForNamespace();

 XMLMapperBuilder#bindMapperForNamespace
 private void bindMapperForNamespace() {
    //获取当前命名空间
    String namespace = builderAssistant.getCurrentNamespace();
    if (namespace != null) {
      Class<?> boundType = null;
      try {
       //当前命名空间是接口而不是其他普通字符串则加载当前类
        boundType = Resources.classForName(namespace);
      } catch (ClassNotFoundException e) {
        //ignore, bound type is not required
      }
      if (boundType != null) {
       //检查当前类型是否已经生成相应MapperProxy代理
        if (!configuration.hasMapper(boundType)) {
          // Spring may not know the real resource name so we set a flag
          // to prevent loading again this resource from the mapper interface
          // look at MapperAnnotationBuilder#loadXmlResource
          //可以发现xml文件和namespace都使用addLoadedResource表示已经加载的资源
          configuration.addLoadedResource("namespace:" + namespace);
          //如果当前类型接口生成对应的Mapper接口代理
          configuration.addMapper(boundType);
        }
      }
    }
  }

   //Configuration#addMapper
  public <T> void addMapper(Class<T> type) {
    mapperRegistry.addMapper(type);
  }
//MapperRegistry#addMapper
public <T> void addMapper(Class<T> type) {
    if (type.isInterface()) {
      if (hasMapper(type)) {
        throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
      }
      boolean loadCompleted = false;
      try {
       //后面再细说bind包下面的类
        knownMappers.put(type, new MapperProxyFactory<T>(type));
        // It's important that the type is added before the parser is run
        // otherwise the binding may automatically be attempted by the
        // mapper parser. If the type is already known, it won't try.
        MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type);
        parser.parse();
        loadCompleted = true;
      } finally {
        if (!loadCompleted) {
          knownMappers.remove(type);
        }
      }
    }
  }

MapperAnnotationBuilder和XMLMapperBuilder类似，不同的是MapperAnnotationBuilder负责解析接口上的方法和注解

public void parse() {
   
    String resource = type.toString();
     //判断当前类型是否加载，
     //前面说了Configuration中的loadedResources可以包含两种资源：
    //mapper文件，namespace（针对加载xml资源）这里还有一种 当前类型(针对加载接口)
    if (!configuration.isResourceLoaded(resource)) {
     //加载mapper.xml 这里证明了可以从接口加载mapper文件，但是要遵守相应的约定
      loadXmlResource();
      configuration.addLoadedResource(resource);
     //同样MapperAnnotationBuilder有MapperBuilderAssistant的实例变量
      assistant.setCurrentNamespace(type.getName());
      parseCache();
      parseCacheRef();
      Method[] methods = type.getMethods();
      //解析方法
      for (Method method : methods) {
        try {
          // issue #237
          if (!method.isBridge()) {//跳过桥接方法
            parseStatement(method);
          }
        } catch (IncompleteElementException e) {
         
          configuration.addIncompleteMethod(new MethodResolver(this, method));
        }
      }
    }
    //重新进行解析未完成的方法
    parsePendingMethods();
  }
 //加载和接口全限定名称一样的映射文件，例：com.test.StudentMapper,com/test/StudentMapper.xml
 private void loadXmlResource() {
    // Spring may not know the real resource name so we check a flag
    // to prevent loading again a resource twice
    // this flag is set at XMLMapperBuilder#bindMapperForNamespace
   //因为spring和mybatis集成即可以配置mapperLocations，也可以配置MapperScannerConfigurer的basePackage ，而mybatis既可以从接口开始扫描，也可以从映射文件开始扫描，为了防止重复加载同一个命名空间，在加载之前先添加到loadedResource中。
   //这里是从xml向接口扫描的过程，即在bindMapperForNamespace中已经调用
   //          configuration.addLoadedResource("namespace:" + namespace);
    if (!configuration.isResourceLoaded("namespace:" + type.getName())) {
      String xmlResource = type.getName().replace('.', '/') + ".xml";
      InputStream inputStream = null;
      try {
        inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
      } catch (IOException e) {
        // ignore, resource is not required
      }
      if (inputStream != null) {
       //这里和之前一样执行mapper文件的加载流程
        XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName());
        xmlParser.parse();
      }
    }
  }

检查缓存注解

  private void parseCache() {
    CacheNamespace cacheDomain = type.getAnnotation(CacheNamespace.class);
    if (cacheDomain != null) {
      Integer size = cacheDomain.size() == 0 ? null : cacheDomain.size();
      Long flushInterval = cacheDomain.flushInterval() == 0 ? null : cacheDomain.flushInterval();
      Properties props = convertToProperties(cacheDomain.properties());
      assistant.useNewCache(cacheDomain.implementation(), cacheDomain.eviction(), flushInterval, size, cacheDomain.readWrite(), cacheDomain.blocking(), props);
    }


  private void parseCacheRef() {
    CacheNamespaceRef cacheDomainRef = type.getAnnotation(CacheNamespaceRef.class);
    if (cacheDomainRef != null) {
      Class<?> refType = cacheDomainRef.value();
      String refName = cacheDomainRef.name();
      if (refType == void.class && refName.isEmpty()) {
        throw new BuilderException("Should be specified either value() or name() attribute in the @CacheNamespaceRef");
      }
      if (refType != void.class && !refName.isEmpty()) {
        throw new BuilderException("Cannot use both value() and name() attribute in the @CacheNamespaceRef");
      }
      String namespace = (refType != void.class) ? refType.getName() : refName;
      assistant.useCacheRef(namespace);
    }
  }
  }

 void parseStatement(Method method) {
    //和XML解析创建SqlSource类似
    Class<?> parameterTypeClass = getParameterType(method);
    LanguageDriver languageDriver = getLanguageDriver(method);
    SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver);
   //如果其中一种注解不为空
    if (sqlSource != null) {
      Options options = method.getAnnotation(Options.class);
      final String mappedStatementId = type.getName() + "." + method.getName();
      Integer fetchSize = null;
      Integer timeout = null;
      StatementType statementType = StatementType.PREPARED;
      ResultSetType resultSetType = ResultSetType.FORWARD_ONLY;
      SqlCommandType sqlCommandType = getSqlCommandType(method);
      boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
      boolean flushCache = !isSelect;
      boolean useCache = isSelect;

      KeyGenerator keyGenerator;
      String keyProperty = "id";
      String keyColumn = null;
      if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
        // first check for SelectKey annotation - that overrides everything else
        SelectKey selectKey = method.getAnnotation(SelectKey.class);
        if (selectKey != null) {
          keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method), languageDriver);
          keyProperty = selectKey.keyProperty();
        } else if (options == null) {
          keyGenerator = configuration.isUseGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
        } else {
          keyGenerator = options.useGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
          keyProperty = options.keyProperty();
          keyColumn = options.keyColumn();
        }
      } else {
        keyGenerator = NoKeyGenerator.INSTANCE;
      }

      if (options != null) {
        if (FlushCachePolicy.TRUE.equals(options.flushCache())) {
          flushCache = true;
        } else if (FlushCachePolicy.FALSE.equals(options.flushCache())) {
          flushCache = false;
        }
        useCache = options.useCache();
        fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; //issue #348
        timeout = options.timeout() > -1 ? options.timeout() : null;
        statementType = options.statementType();
        resultSetType = options.resultSetType();
      }

      String resultMapId = null;
      ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);
      if (resultMapAnnotation != null) {
        String[] resultMaps = resultMapAnnotation.value();
        StringBuilder sb = new StringBuilder();
        for (String resultMap : resultMaps) {
          if (sb.length() > 0) {
            sb.append(",");
          }
          sb.append(resultMap);
        }
        resultMapId = sb.toString();
      } else if (isSelect) {
        resultMapId = parseResultMap(method);
      }

      assistant.addMappedStatement(
          mappedStatementId,
          sqlSource,
          statementType,
          sqlCommandType,
          fetchSize,
          timeout,
          // ParameterMapID
          null,
          parameterTypeClass,
          resultMapId,
          getReturnType(method),
          resultSetType,
          flushCache,
          useCache,
          // TODO gcode issue #577
          false,
          keyGenerator,
          keyProperty,
          keyColumn,
          // DatabaseID
          null,
          languageDriver,
          // ResultSets
          options != null ? nullOrEmpty(options.resultSets()) : null);
    }
  }

//当前方法只有一个参数，返回参数本身的类型
//多个参数返回ParamMap
//参数不是RowBounds、ResultHandler 的子类
private Class<?> getParameterType(Method method) {
    Class<?> parameterType = null;
    Class<?>[] parameterTypes = method.getParameterTypes();
    for (Class<?> currentParameterType : parameterTypes) {
      if (!RowBounds.class.isAssignableFrom(currentParameterType) && !ResultHandler.class.isAssignableFrom(currentParameterType)) {
        if (parameterType == null) {
          parameterType = currentParameterType;
        } else {
          // issue #135
          parameterType = ParamMap.class;
        }
      }
    }
    return parameterType;
  }
//获取语言驱动，为空获取当前默认XMLLanguageDriver
 private LanguageDriver getLanguageDriver(Method method) {
    Lang lang = method.getAnnotation(Lang.class);
    Class<?> langClass = null;
    if (lang != null) {
      langClass = lang.value();
    }
    return assistant.getLanguageDriver(langClass);
  }

 private SqlSource getSqlSourceFromAnnotations(Method method, Class<?> parameterType, LanguageDriver languageDriver) {
    try {
      Class<? extends Annotation> sqlAnnotationType = getSqlAnnotationType(method);
      Class<? extends Annotation> sqlProviderAnnotationType = getSqlProviderAnnotationType(method);
      if (sqlAnnotationType != null) {
        if (sqlProviderAnnotationType != null) {
        //两个注解不能同时使用
          throw new BindingException("You cannot supply both a static SQL and SqlProvider to method named " + method.getName());
        }
        Annotation sqlAnnotation = method.getAnnotation(sqlAnnotationType);
        final String[] strings = (String[]) sqlAnnotation.getClass().getMethod("value").invoke(sqlAnnotation);
        return buildSqlSourceFromStrings(strings, parameterType, languageDriver);
      } else if (sqlProviderAnnotationType != null) {
        Annotation sqlProviderAnnotation = method.getAnnotation(sqlProviderAnnotationType);
        return new ProviderSqlSource(assistant.getConfiguration(), sqlProviderAnnotation, type, method);
      }
      return null;
    } catch (Exception e) {
      throw new BuilderException("Could not find value method on SQL annotation.  Cause: " + e, e);
    }
  }

到此整个mapper流程加载就结束了。parseConfiguration也随之结束了，XMLConfigBuilder的parse也结束了。
执行加载的最后一个节点生成DefaultSqlSessionFactory

  public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
  }

mapper流程加载总结：
//TODO


mybatis加载流程总结：
//TODO