resultMap 結果集映射（one to many/many to one）

1.userInfo-mapping.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="oneToMany">
    <!-- 一對多 -->
    <!-- resultMap 結果集映射 -->
    <!-- type 是數據表類型   id 是結果集映射名稱
        關聯查詢兩張表有相同的列名必須給於別名     
                如果數據庫表的列名和實體類的字段名一致可以用autoMapping自動映射 
    -->
    <resultMap type="com.mybatis.pojo.UserInfo" id="userinfo" >
        <!-- 
            結果列名  填充到userinfo對應的字段上 
            column    結果集列名
            javaType  實體類的字段類型
            property  實體類字段名
         -->
        <result column="id" javaType="string" property="id" />
        <result column="name" javaType="string" property="name"/>
        <result column="password" javaType="string" property="password"/>
        <!-- collection 一對多

                property  是一的一方的orders字段名  (private List<Orders> orders)
                javaType  是一的一方的orders字段的類型 java.util.List
                select   要執行的sql語句的映射名   會自動填充到List<Orders> orders中
                column   要傳人的關聯的列名
                autoMapping 類型的自動映射
         -->
        <collection property="orders" javaType="list" select="queryOrdersById" column="id" >
            <!-- 
            結果列名  填充到orders對應的字段中間的泛型類( private List<Orders> orders)
            column    結果集列名
            javaType  實體類的字段類型
            property  實體類字段名
         -->
            <result column="id" javaType="string" property="id"/>
            <result column="u_id" javaType="string" property="u_id"/>
            <result column="o_count" javaType="string" property="o_count"/>
            <result column="name" javaType="string" property="name"/>
        </collection>

    </resultMap>

    <!-- 查詢userinfo 使用userinfo 結果集    傳人要查詢的id -->
    <select id="queryUserinfoById" resultMap="userinfo" parameterType="int">
        select * from  userinfo where id =#{id} 
    </select>

    <!-- 查詢orders 使用實體類包名+類名 （com.mybatis.pojo.Orders）   傳人的關聯的列名的類型 -->
    <select id="queryOrdersById" resultType="com.mybatis.pojo.Orders" parameterType="String" >
        select * from orders where u_id =#{id}
    </select>

</mapper>

2.orders-mapping.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="manyToOne">
    <!-- 多對一 -->
    <!-- resultMap結果集映射 -->
    <resultMap type="com.mybatis.pojo.Orders" id="orders">
        <result column="id" javaType="string" property="id"/>
        <result column="u_id" javaType="string" property="u_id"/>
        <result column="o_count" javaType="string" property="o_count"/>
        <result column="name" javaType="string" property="name"/>
        <!-- 查詢出userinfo 信息填充至userinfo 字段中  javaType="com.mybatis.pojo.UserInfo" 使用id列做關聯 -->
        <association property="userinfo"  javaType="com.mybatis.pojo.UserInfo" select="queryUserinfoById" column="u_id">
            <result column="id" javaType="string" property="id" />
            <result column="name" javaType="string" property="name"/>
            <result column="password" javaType="string" property="password"/>
        </association>
    </resultMap>
    <select id="queryUserinfoById" resultType="com.mybatis.pojo.UserInfo" parameterType="string">
        select * from  userinfo where id =#{id} 
    </select>
    <!-- 引用resultMap orders -->
    <select id="queryOrdersById" resultMap="orders" parameterType="int" >
        select * from orders where id =#{id}
    </select>
</mapper>

3.userinfo.java

package com.mybatis.pojo;

import java.util.List;

public class UserInfo {
    private String id      ;
    private String name     ;
    private String  password ;
    private List<Orders> orders;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

4.orders.java

package com.mybatis.pojo;

public class Orders {
    private String id     ;
    private String u_id   ;
    private String   o_count;
    private String name;
    private UserInfo userinfo;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getU_id() {
        return u_id;
    }
    public void setU_id(String u_id) {
        this.u_id = u_id;
    }
    public String getO_count() {
        return o_count;
    }
    public void setO_count(String o_count) {
        this.o_count = o_count;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}