JdbcTemplate详解 - 2

JdbcTemplate详解 - 2

http://tianya23.blog.51cto.com/1081650/275292

1、由于之前JdbcTemplate的程序需要编写一堆的RowMapper的映射文件，显得有些臃肿，最好是根据pojo类和字段的名称进行自动的对应， 所以SimpleJdbcTemplate支持使用Pojo中的属性进行自动赋值， 语法为':'开头。

public class UserDaoSpringImpl implements UserDao {
   private SimpleJdbcTemplate simpleJdbcTemplate = new SimpleJdbcTemplate(
       JdbcUtils.getDataSource());
 
  public void addUser(User user) {
     String sql = "insert into user (name, money, birthday) values (:name, :money, :birthday)";
     SqlParameterSource param = new BeanPropertySqlParameterSource(user);
     KeyHolder keyHolder = new GeneratedKeyHolder();
     this.simpleJdbcTemplate.getNamedParameterJdbcOperations().update(sql,
         param, keyHolder);
     user.setId(keyHolder.getKey().intValue());
   }
 
  public void delete(User user) {
     String sql = "delete from user where id=?";
     this.simpleJdbcTemplate.update(sql, user.getId());
   }
 
  public User findUser(String loginName, String password) {
     String sql = "select id, name, money, birthday    from user where name=?";
     return this.simpleJdbcTemplate.queryForObject(sql,
         ParameterizedBeanPropertyRowMapper.newInstance(User.class),
         loginName);
   }
 
  public User getUser(int userId) {
     String sql = "select id, name, money, birthday    from user where id=?";
     return this.simpleJdbcTemplate.queryForObject(sql,
         ParameterizedBeanPropertyRowMapper.newInstance(User.class),
         userId);
   }
 
  public void update(User user) {
     String sql = "update user set name=?, birthday=?, money=? where id=? ";
     this.simpleJdbcTemplate.update(sql, user.getName(), user.getBirthday(),
         user.getMoney(), user.getId());
 
    sql = "update user set name=:name, birthday=:birthday, money=:money where id=:id ";
     this.simpleJdbcTemplate.update(sql, new BeanPropertySqlParameterSource(
         user));
   }
 
}

其中使用的JdbcUtils获取数据源的代码如下：

public final class JdbcUtils {
   private static String url = "jdbc:mysql://localhost:3306/jdbc";
   private static String user = "root";
   private static String password = "";
   private static DataSource myDataSource = null;
 
  private JdbcUtils() {
   }
 
  static {
     try {
       Class.forName("com.mysql.jdbc.Driver");
       // myDataSource = new MyDataSource2();
       Properties prop = new Properties();
       // prop.setProperty("driverClassName", "com.mysql.jdbc.Driver");
       // prop.setProperty("user", "user");
 
      InputStream is = JdbcUtils.class.getClassLoader()
           .getResourceAsStream("dbcpconfig.properties");
       prop.load(is);
       myDataSource = BasicDataSourceFactory.createDataSource(prop);
     } catch (Exception e) {
       throw new ExceptionInInitializerError(e);
     }
   }
 
  public static DataSource getDataSource() {
     return myDataSource;
   }
 
  public static Connection getConnection() throws SQLException {
     // return DriverManager.getConnection(url, user, password);
     return myDataSource.getConnection();
   }
 
  public static void free(ResultSet rs, Statement st, Connection conn) {
     try {
       if (rs != null)
         rs.close();
     } catch (SQLException e) {
       e.printStackTrace();
     } finally {
       try {
         if (st != null)
           st.close();
       } catch (SQLException e) {
         e.printStackTrace();
       } finally {
         if (conn != null)
           try {
             conn.close();
             // myDataSource.free(conn);
           } catch (Exception e) {
             e.printStackTrace();
           }
       }
     }
   }
 }

2、 完成相同映射的类还包括：NamedParameterJdbcTemplate， 它将之前的占位符‘？’进行了取名，方便程序的阅读。 不过这样的SQL不能再数据库中直接执行，需要有Spring进行转换。

public class NamedJdbcTemplate {
   static NamedParameterJdbcTemplate named = new NamedParameterJdbcTemplate(
       JdbcUtils.getDataSource());
 
  /**
     * @param args
     */
   public static void main(String[] args) {
     User user = new User();
     user.setMoney(10);
     user.setId(2);
     System.out.println(findUser1(user));
   }
 
  static void addUser(User user) {
     String sql = "insert into user(name,birthday, money) values (:name,:birthday,:money) ";
     SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
     KeyHolder keyHolder = new GeneratedKeyHolder();
     named.update(sql, ps, keyHolder);
     int id = keyHolder.getKey().intValue();
     user.setId(id);
     
     Map map = keyHolder.getKeys();
   }
 
  static User findUser(User user) {
     String sql = "select id, name, money, birthday    from user "
         + "where money > :m and id < :id";
     Map params = new HashMap();
     // params.put("n", user.getName());
     params.put("m", user.getMoney());
     params.put("id", user.getId());
     Object u = named.queryForObject(sql, params, new BeanPropertyRowMapper(
         User.class));
     return (User) u;
   }
 
  static User findUser1(User user) {
     String sql = "select id, name, money, birthday    from user "
         + "where money > :money and id < :id";
     SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
     Object u = named.queryForObject(sql, ps, new BeanPropertyRowMapper(User.class));
     return (User) u;
   }
 
}

【注意】

1、BeanPropertyRowMapper完成了对象到数据库字段的映射关系， 可以不再使用RowMapper来一一对应起来。如果RowMapper只使用1次，则可以直接使用内部类来完成，而不再需要专门的写一个类。

2、KeyHolder， 其中保存了数据库中操作的主键，取得操作的主键后， 方便对进行操作的记录进行其他动作。



总之：利用反射技术，减少的了不必要的rowmapper，提高了效率