MyBatis配置文件UserMapper.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="com.kaishengit.mapper.UserMapper">

    <resultMap id="userWithCountryMap" type="com.kaishengit.entity.User">
        <id column="id" property="id"/>
        <result column="username" property="userName"/>
        <result column="address" property="address"/>
        <result column="password" property="passWord"/>
        <result column="countryid" property="countryId"/>
        <association property="country" javaType="com.kaishengit.entity.Country" column="countryid" select="com.kaishengit.mapper.CountryMapper.findById"/>
    </resultMap>

    <select id="findById" resultMap="userWithCountryMap">
        SELECT id,username,address,password,countryid FROM t_user
        WHERE id = #{id}
    </select>
    <!--开启二级缓存-->   
    <cache/>
    <!--批量添加-->
    <insert id="batchSaveUser">
        INSERT INTO t_user (username,address,password)
        VALUES
        <foreach collection="userList" item="user" separator=",">
            (#{user.userName},#{user.passWord},#{user.address})
        </foreach>
    </insert>

    <!--左联接查询-->
    <select id="find" parameterType="int" resultType="user">
         SELECT
            tu.id,
            username,
            address,
            PASSWORD,
            countryid AS 'country.id',
            tc.countname AS 'country.countname'
        FROM
            t_user AS tu
        LEFT JOIN t_country AS tc ON tu.countryid = tc.id
        WHERE
            tu.id = #{id}
    </select>
    <!-- 根据id查询user对象-->
    <select id="findById" parameterType="int" resultType="user" useCache="false">
        SELECT * FROM t_user WHERE id=#{id}
    </select>
    <!--查询全部-->
    <select id="findAll" resultType="user">
        SELECT * FROM t_user
    </select>
    <!--增加对象-->
    <insert id="add" parameterType="user">
        INSERT INTO t_user (username,address,password,countryid) VALUES (#{userName},#{address},#{passWord},#{countryId})
    </insert>
    <!--修改-->
    <update id="update" parameterType="user">
        UPDATE t_user SET username = #{userName},address = #{address},password = #{passWord},countryid = #{countryId}
        WHERE id = #{id}
    </update>
    <!--删除-->
    <delete id="delete" parameterType="int">
        DELETE FROM t_user WHERE id = #{id}
    </delete>
    <select id="page" resultType="user">
        SELECT * FROM t_user limit #{offset},#{size}
    </select>

    <resultMap id="userWithTagMap" type="com.kaishengit.entity.User">
        <id column="id" property="id"/>
        <result column="username" property="userName"/>
        <result column="address" property="address"/>
        <result column="password" property="passWord"/>
        <result column="countryid" property="countryId"/>
        <collection property="tagList" ofType="com.kaishengit.entity.Tag">
            <id column="tag_id" property="id"/>
            <result column="tag_name" property="tagName"/>
        </collection>
    </resultMap>

    <select id="findByIdWithTag" parameterType="int" resultMap="userWithTagMap">
        SELECT
            t_user.id,
            username,
            address,
            PASSWORD,
            countryid,
            t_tag.id AS 'tag_id',
            tag_name
        FROM
            t_user
        INNER JOIN user_tag ON t_user.id = user_tag.user_id
        INNER JOIN t_tag ON t_tag.id = user_tag.tag_id
        WHERE
            t_user.id = #{userId}
    </select>

</mapper>