mybatis 多表查询二

public class User {
    private Integer id;
    private String name;
    private Integer gender;
    private Integer age;
    private Address address;
    ......
}
public class Address {
    private Integer id;
    private String province;
    private String city;
    private String district;
}

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"      
 "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="com.xiang.mapper.UserMapper">
  <!-- 嵌套结果 -->
    <resultMap type="com.xiang.domain.User" id="UserResultMap">
        <id property="id" column="userId" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <result property="name" column="name" jdbcType="VARCHAR" javaType="java.lang.String"/>
        <result property="gender" column="gender" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <result property="age" column="age" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <association property="address" javaType="com.xiang.domain.Address">
            <id property="id" column="id" jdbcType="INTEGER" javaType="java.lang.Integer"/>
            <result property="province" column="province" jdbcType="VARCHAR" javaType="java.lang.String"/>
            <result property="city" column="city" jdbcType="VARCHAR" javaType="java.lang.String"/>
            <result property="district" column="district" jdbcType="VARCHAR" javaType="java.lang.String"/>
            <result property="detail" column="detail" jdbcType="VARCHAR" javaType="java.lang.String"/>
        </association>
    </resultMap>

    <select id="findById" parameterType="int" resultMap="UserResultMap">
       SELECT u.id userId,u.name,u.gender,u.age,a.id,a.province,a.city,a.district,a.detail 
       FROM user u LEFT JOIN address a on u.addressId = a.id where u.id = #{id}
    </select>

    <select id="findAll" parameterType="int" resultMap="UserResultMap">
       SELECT u.id userId,u.name,u.gender,u.age,a.id,a.province,a.city,a.district,a.detail 
       FROM user u LEFT JOIN address a on u.addressId = a.id 
    </select>
</mapper>

public interface UserMapper {
  public User findById(Integer id);
    public List<User> findAll(); 
}

public class UserDao {
 public User findById(Integer id){
        User user = new User();
      SqlSession sqlSession = null;
        sqlSession = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        if (sqlSession != null) {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
          user = userMapper.findById(id);
          sqlSession.close();
      }
    return user;
 };
   public List<User> findAll(){
       List<User> users = new ArrayList<User>();
        SqlSession sqlSession = null;
        sqlSession = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        if (sqlSession != null) {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
          users = userMapper.findAll();
            sqlSession.close();
      }
    return users;
    }; 
}

public class UserService {
 public User findById(String id){
     UserDao userDao = new UserDao();
     User user = new User();
      if (id != null && !"".equals(id.trim())) {
           user = userDao.findById(Integer.valueOf(id));
        }
        return user;
 };
   public List<User> findAll(){
       UserDao userDao = new UserDao();
     List<User> users = new ArrayList<User>();
        users = userDao.findAll();
       return users;
    }; 
}

<resultMap type="com.xiang.domain.User" id="UserResultMap">
        <id property="id" column="id" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <result property="name" column="name" jdbcType="VARCHAR" javaType="java.lang.String"/>
        <result property="gender" column="gender" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <result property="age" column="age" jdbcType="INTEGER" javaType="java.lang.Integer"/>
        <association property="address"  javaType="com.xiang.domain.Address" column="addressId" select="findAddress"></association>
    </resultMap>
 
    <select id="findAddress" parameterType="int" resultType="com.xiang.domain.Address">
        SELECT id,province,city,district,detail FROM address WHERE id=#{id}
    </select>

    <select id="findById" parameterType="int" resultMap="UserResultMap">
        SELECT id,name,gender,age,addressId FROM user where id=#{id}
    </select>

    <select id="findAll" parameterType="int" resultMap="UserResultMap">
        SELECT id,name,gender,age,addressId FROM user
    </select>