Mybatis使用篇之十二：实现物理分页

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Mybatis使用篇

Mybatis 物理分页

Mybatis的自带分页方法只是逻辑分页，如果数据量很大，内存会溢出，不知道为什么开源组织不在里面实现类似Hibernate的物理分页处理方法。在不改动Mybatis源代码的情况下，怎么使Mybatis支持物理分页呢？下面我们来看看。

（1）新建一个Java类Dialect.java，该类的内容如下：

package org.mybatis.extend.interceptor;

public abstract class Dialect {

	public static enum Type{
		MYSQL,
		ORACLE
	}
	
	public abstract String getLimitString(String sql, int skipResults, int maxResults);
	
}

（2）新建一个Java类OracleDialect.java，该类继承Dialect 类，具体的内容如下：

package org.mybatis.extend.interceptor;

public class OracleDialect extends Dialect{

	/* (non-Javadoc)
	 * @see org.mybatis.extend.interceptor.IDialect#getLimitString(java.lang.String, int, int)
	 */
	@Override
	public String getLimitString(String sql, int offset, int limit) {

		sql = sql.trim();
		StringBuffer pagingSelect = new StringBuffer(sql.length() + 100);
		
		pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
		
		pagingSelect.append(sql);
		
		pagingSelect.append(" ) row_ ) where rownum_ > ").append(offset).append(" and rownum_ <= ").append(offset + limit);
		
		return pagingSelect.toString();
	}

}

（3）新建一个Mybaits的拦截器PaginationInterceptor.java，实现Interceptor接口，该类的内容如下：

package org.mybatis.extend.interceptor;

import java.sql.Connection;
import java.util.Map;
import java.util.Properties;

import org.apache.ibatis.executor.parameter.DefaultParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


@Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class})})
public class PaginationInterceptor implements Interceptor {
	//日志对象
	protected static Logger log = LoggerFactory.getLogger(PaginationInterceptor.class);
	/* (non-Javadoc)
	 * @see org.apache.ibatis.plugin.Interceptor#intercept(org.apache.ibatis.plugin.Invocation)
	 */
	@Override
	public Object intercept(Invocation invocation) throws Throwable {
		StatementHandler statementHandler = (StatementHandler)invocation.getTarget();
		MetaObject metaStatementHandler = MetaObject.forObject(statementHandler);
		
		RowBounds rowBounds = (RowBounds)metaStatementHandler.getValue("delegate.rowBounds");
		if(rowBounds == null || rowBounds == RowBounds.DEFAULT){
			return invocation.proceed();
		}
		
		DefaultParameterHandler defaultParameterHandler = (DefaultParameterHandler)metaStatementHandler.getValue("delegate.parameterHandler");
		Map parameterMap = (Map)defaultParameterHandler.getParameterObject();
		Object sidx = parameterMap.get("_sidx");
		Object sord = parameterMap.get("_sord");
		
		String originalSql = (String)metaStatementHandler.getValue("delegate.boundSql.sql");
		
		if(sidx != null && sord != null){
			originalSql = originalSql + " order by " + sidx + " " + sord;
		}
		
		Configuration configuration = (Configuration)metaStatementHandler.getValue("delegate.configuration");
        
                            Dialect.Type databaseType  = null;
		try{
			databaseType = Dialect.Type.valueOf(configuration.getVariables().getProperty("dialect").toUpperCase());
		} catch(Exception e){
			//ignore
		}
		if(databaseType == null){
			throw new RuntimeException("the value of the dialect property in configuration.xml is not defined : " + configuration.getVariables().getProperty("dialect"));
		}
		Dialect dialect = null;
		switch(databaseType){
			case ORACLE:
				dialect = new OracleDialect();
				break;
			case MYSQL://需要实现MySQL的分页逻辑
				break;
				
		}
		
		
		metaStatementHandler.setValue("delegate.boundSql.sql", dialect.getLimitString(originalSql, rowBounds.getOffset(), rowBounds.getLimit()) );
		metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET );
		metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT );
		if(log.isDebugEnabled()){
			BoundSql boundSql = statementHandler.getBoundSql();
			log.debug("生成分页SQL : " + boundSql.getSql());
		}
		return invocation.proceed();
	}

	/* (non-Javadoc)
	 * @see org.apache.ibatis.plugin.Interceptor#plugin(java.lang.Object)
	 */
	@Override
	public Object plugin(Object target) {
		return Plugin.wrap(target, this);
	}

	/* (non-Javadoc)
	 * @see org.apache.ibatis.plugin.Interceptor#setProperties(java.util.Properties)
	 */
	@Override
	public void setProperties(Properties arg0) {
		// TODO Auto-generated method stub
		
	}

}

（4）将Mybatis的拦截器配置到Mybatis的全局配置文件(mybatis.cfg.xml)中，具体如下：

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE configuration PUBLIC 
    "-//mybatis.org//DTD Config 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
	<properties>
    	      <property name="dialect" value="oracle"/>
	</properties>
	    
 	<plugins>
	        <plugin interceptor="org.mybatis.extend.interceptor.PaginationInterceptor"/>
	</plugins>
	   
</configuration>

（5）使用方法同Mybatis逻辑分页一样，拦截器会自动拦截执行SQL的地方，加上分页代码：

getSqlSession().selectList(sqlId, paramMap,new RowBounds(pageId, pageSize));

分享到：

Oracle查询表结构的常用语句 | Mybatis使用篇之四：整合Spring

2012-02-11 22:58
浏览 27641
评论(7)
分类:企业架构
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7 楼 Dreamer_1029 2014-09-27

阿里内部看到的url，建议楼主继续补全

6 楼 DR-YangLong 2013-12-20

不用那么麻烦，求关注http://dr-yanglong.iteye.com/blog/1992383

5 楼 sunney2010 2013-02-02

进入PaginationInterceptor之前就报错了。在全局配置去了这个拦截器就正常，求解，错误为：
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.lang.NullPointerException
### Cause: java.lang.NullPointerException
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:73)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:365)
at $Proxy14.selectList(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:202)
at com.sunney.userInfo.dao.Impl.UserInfoDaoImpl.queryUserInfo(UserInfoDaoImpl.java:48)
at com.sunney.userInfo.service.Impl.UserInfoServiceImpl.queryUserInfo(UserInfoServiceImpl.java:39)
at com.sunney.userInfo.service.Impl.UserInfoServiceImpl$$FastClassByCGLIB$$2d83dad1.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
at com.sunney.userInfo.service.Impl.UserInfoServiceImpl$$EnhancerByCGLIB$$9e960c26.queryUserInfo(<generated>)
at com.sunney.userInfo.UserInfoTest.queryUserInfoTest(UserInfoTest.java:41)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:292)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.lang.NullPointerException
### Cause: java.lang.NullPointerException
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:355)
... 43 more
Caused by: java.lang.NullPointerException
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:101)
... 48 more

org.springframework.transaction.UnexpectedRollbackException: Transaction rolled back because it has been marked as rollback-only
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:717)
at org.springframework.test.context.transaction.TransactionalTestExecutionListener$TransactionContext.endTransaction(TransactionalTestExecutionListener.java:591)
at org.springframework.test.context.transaction.TransactionalTestExecutionListener.endTransaction(TransactionalTestExecutionListener.java:297)
at org.springframework.test.context.transaction.TransactionalTestExecutionListener.afterTestMethod(TransactionalTestExecutionListener.java:192)
at org.springframework.test.context.TestContextManager.afterTestMethod(TestContextManager.java:396)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:91)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:292)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

4 楼 sunney2010 2013-02-02

进入PaginationInterceptor之前就报错了。求解：

3 楼 flynofry 2012-12-11

您好！参考/转载文章
http://www.cnblogs.com/jcli/archive/2011/08/09/2132222.html
其实可以标注一下出处。

2 楼 say4ever2u 2012-11-22

say4ever2u 写道

第41parameterMap 没做校验就直接使用， 40行有可能取到null

我确实不明白 41 42这两行是干什么的 _sidx _sord是干什么用的，调试也没有发现他们，所以报错，呵呵希望给于说明下

1 楼 say4ever2u 2012-11-22