Mybatis基于XML配置SQL映射器(二)

Mybatis之XML注解

之前已经讲到通过 mybatis-generator 生成mapper映射接口和相关的映射配置文件:

下面我们将详细的讲解具体内容

首先我们新建映射接口文档  sysUserExtMapper.java,同时新增相关配置文件sysUserExtMapper.xml。通过操作这两个类我们来讲解具体内容。

映射语句

MyBatis提供了多种元素来配置不同类型的语句，如SELECT，INSERT，UPDATE，DELETE。接下来让我们看看如何具体配置映射语句。

INSERT语句

 一个INSERT SQL语句可以在<insert>元素在sysUserExtMapper.xml中配置，如下所示：

    <insert id="insertsysUser" parameterType="com.goku.mybatis.model.sysUser">
     insert into sys_user (id, username, password,
      name, sex, status, org_id,
      email, idcard, is_admin,
      sort, mobile, stationid
      )
    values (#{id,jdbcType=VARCHAR}, #{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR},
      #{name,jdbcType=VARCHAR}, #{sex,jdbcType=VARCHAR}, #{status,jdbcType=CHAR}, #{orgId,jdbcType=VARCHAR},
      #{email,jdbcType=VARCHAR}, #{idcard,jdbcType=VARCHAR}, #{isAdmin,jdbcType=VARCHAR},
      #{sort,jdbcType=BIGINT}, #{mobile,jdbcType=VARCHAR}, #{stationid,jdbcType=LONGVARCHAR}
      )
    </insert>

同时在 sysUserExtMapper.java接口中添加相应的方法

package com.goku.mybatis.mapper.ext;

import com.goku.mybatis.model.sysUser;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

/**
 * Created by nbfujx on 2017/10/14.
 */
public interface sysUserExtMapper {

    int  insertsysUser(sysUser sysuser));
}

 增加相对应单元测试查看相关效果

package test.com.goku.mybatis.mapper.ext;

import com.goku.mybatis.WebapiApplication;
import com.goku.mybatis.mapper.ext.sysUserExtMapper;
import com.goku.mybatis.model.sysUser;
import com.goku.mybatis.service.impl.sysUserServiceImpl;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import static org.junit.Assert.*;

/**
 * Created by nbfujx on 2017/10/23.
 */
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = WebapiApplication.class)
public class sysUserExtMapperTest  {

    private Logger logger = LoggerFactory.getLogger(sysUserExtMapperTest.class);

    @Autowired
    private sysUserExtMapper sysuserextmapper;

    @Test
    public void insertsysUser() throws Exception {
       sysUser sysuser=new sysUser();
        sysuser.setId("222");
        sysuser.setOrgId("2");
        int i=sysuserextmapper.insertsysUser(sysuser);
        this.logger.info("执行成功个数："+i);
    }

}

执行效果

【自动生成主键】

在上述的INSERT语句中，我们为可以自动生成（auto-generated）主键的列 id 插入值。

我们可以使用useGeneratedKeys 和 keyProperty属性让数据库生成AUTO_INCREMENT列的值，并将生成的值设置到其中一个输入对象属性内，如下所示：

    <insert id="insertsysUser2" parameterType="com.goku.mybatis.model.sysUser" useGeneratedKeys="true"
            keyProperty="id">
        insert into sys_user ( username, password,
        name, sex, status, org_id,
        email, idcard, is_admin,
        sort, mobile, stationid
        )
        values ( #{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR},
        #{name,jdbcType=VARCHAR}, #{sex,jdbcType=VARCHAR}, #{status,jdbcType=CHAR}, #{orgId,jdbcType=VARCHAR},
        #{email,jdbcType=VARCHAR}, #{idcard,jdbcType=VARCHAR}, #{isAdmin,jdbcType=VARCHAR},
        #{sort,jdbcType=BIGINT}, #{mobile,jdbcType=VARCHAR}, #{stationid,jdbcType=LONGVARCHAR}
        )
    </insert>

有些数据库如Oracle并不支持 AUTO_INCREMENT 列，其使用序列（SEQUENCE），或者其他查询（uuid）来生成主键值，如下所示：

 <insert id="insertsysUser3" parameterType="com.goku.mybatis.model.sysUser">
        <selectKey keyProperty="id" resultType="java.lang.String" order="BEFORE">
              SELECT replace(uuid(),'-','')  AS id
        </selectKey>
        insert into sys_user (id, username, password,
        name, sex, status, org_id,
        email, idcard, is_admin,
        sort, mobile, stationid
        )
        values (#{id,jdbcType=VARCHAR}, #{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR},
        #{name,jdbcType=VARCHAR}, #{sex,jdbcType=VARCHAR}, #{status,jdbcType=CHAR}, #{orgId,jdbcType=VARCHAR},
        #{email,jdbcType=VARCHAR}, #{idcard,jdbcType=VARCHAR}, #{isAdmin,jdbcType=VARCHAR},
        #{sort,jdbcType=BIGINT}, #{mobile,jdbcType=VARCHAR}, #{stationid,jdbcType=LONGVARCHAR}
        )
    </insert>

UPDATE 语句

一个UPDATE SQL语句可以在<update>元素在映射器XML配置文件中配置，如下所示：

    <update id="updateUser" parameterType="com.goku.mybatis.model.sysUser">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        update sys_user
        set username = #{username,jdbcType=VARCHAR},
        password = #{password,jdbcType=VARCHAR},
        name = #{name,jdbcType=VARCHAR},
        sex = #{sex,jdbcType=VARCHAR},
        status = #{status,jdbcType=CHAR},
        org_id = #{orgId,jdbcType=VARCHAR},
        email = #{email,jdbcType=VARCHAR},
        idcard = #{idcard,jdbcType=VARCHAR},
        is_admin = #{isAdmin,jdbcType=VARCHAR},
        sort = #{sort,jdbcType=BIGINT},
        mobile = #{mobile,jdbcType=VARCHAR},
        stationid = #{stationid,jdbcType=LONGVARCHAR}
        where id = #{id,jdbcType=VARCHAR}
    </update>

同时在映射器接口中添加相应的方法

    int updateUser(sysUser sysuser);

 增加相对应单元测试查看相关效果

 @Test
    public void updateUser() throws Exception {
        sysUser sysuser=sysuserextmapper.selectByUsername("1");
        sysuser.setPassword("3");
        sysuser.setOrgId("2");
        int i=sysuserextmapper.updateUser(sysuser);
        this.logger.info("执行成功个数："+i);
    }

测试效果

DELETE 语句

一个DELETE SQL语句可以在<delete>元素在映射器XML配置文件中配置，如下所示：

    <delete id="deleteByUserName" parameterType="java.lang.String">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        delete from sys_user
        where username = #{username,jdbcType=VARCHAR}
    </delete>

同时在映射器接口中添加相应的方法

    int deleteByUserName(@Param("username") String username);

 增加相对应单元测试查看相关效果

 @Test
    public void deleteByUserName() throws Exception {
        int i=sysuserextmapper.deleteByUserName("1");
        this.logger.info("执行成功个数："+i);
    }

测试效果

SELECT 语句

一个SELECT SQL语句可以在<select>元素在映射器XML配置文件中配置，如下所示：

   <select id="selectByUsername" parameterType="java.lang.String" resultMap="BaseResultExtMap">
        select
        <include refid="Base_Ext_Column_List" />
        from sys_user
        where username = #{username,jdbcType=VARCHAR}
    </select>

同时在映射器接口中添加相应的方法

    sysUser selectByUsername(String username);

 增加相对应单元测试查看相关效果

  @Test
    public void selectByUsername() throws Exception {
        sysUser user= sysuserextmapper.selectByUsername("444");
        System.out.println(user.getId());
    }

测试效果

 结果集映射ResultMaps

简单ResultMap

在<select>语句中，我们使用了resultMap属性，而不是resultType来引用映射。

当<select>语句中配置了resutlMap属性，MyBatis会使用此数据库列名与对象属性映射关系来填充JavaBean中的属性。

 <select id="selectByUsername" parameterType="java.lang.String" resultMap="BaseResultExtMap">
        select
        <include refid="Base_Ext_Column_List" />
        from sys_user
        where username = #{username,jdbcType=VARCHAR}
    </select>

让我们来看另外一个<select>映射语句定义的例子，怎样将查询结果填充到HashMap中。如下所示：

    <select id="selectUserByUsername"  resultType="java.util.HashMap">
        select  username,password from sys_user where username = #{username,jdbcType=VARCHAR}
    </select>

在上述的<select>语句中，我们将resultType配置成map，即java.util.HashMap的别名。在这种情况下，结果集的列名将会作为Map中的key值，而列值将作为Map的value值。

映射器接口中添加相应的方法

    Map<String, String> selectUserByUsername(@Param("username") String username);

让我们再看一个 使用resultType=”map”,返回多行结果的例子：

    <select id="selectUserByOrgid"  resultType="java.util.HashMap">
        select  username,password from sys_user where org_id = #{orgid,jdbcType=VARCHAR}
        <if test="orderFiled != null" >
            order by  ${orderFiled}
            <if test="orderSort != null" >
                ${orderSort}
            </if>
        </if>
    </select>

映射器接口中添加相应的方法

List<Map<String, String>> selectUserByOrgid(@Param("orgid") String orgid, @Param("orderSort") String orderSort, @Param("orderFiled") String orderFiled);

拓展ResultMap

首先我们要在 sys_User中增加 sys_user_info对象。下面同理

 private sysUserInfo sysuserinfo;

    public sysUserInfo getSysuserinfo() {
        return sysuserinfo;
    }

    public void setSysuserinfo(sysUserInfo sysuserinfo) {
        this.sysuserinfo = sysuserinfo;
    }

 我们可以从从另外一个<resultMap>，拓展出一个新的<resultMap>，这样，原先的属性映射可以继承过来，以实现。

  <resultMap id="UserinfoBaseResultExtMap" type="com.goku.mybatis.model.sysUser" extends="BaseResultExtMap">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        <result column="address" jdbcType="VARCHAR" property="sysuserinfo.address" />
        <result column="post_code" jdbcType="VARCHAR" property="sysuserinfo.postCode" />
        <result column="height" jdbcType="VARCHAR" property="sysuserinfo.height" />
        <result column="weight" jdbcType="VARCHAR" property="sysuserinfo.weight" />
        <result column="birthday" jdbcType="DATE" property="sysuserinfo.birthday" />
        <result column="blood" jdbcType="VARCHAR" property="sysuserinfo.blood" />
        <result column="culture" jdbcType="VARCHAR" property="sysuserinfo.culture" />
        <result column="finish_school_date" jdbcType="DATE" property="sysuserinfo.finishSchoolDate" />
        <result column="folk" jdbcType="VARCHAR" property="sysuserinfo.folk" />
        <result column="government" jdbcType="VARCHAR" property="sysuserinfo.government" />
        <result column="homepage" jdbcType="VARCHAR" property="sysuserinfo.homepage" />
        <result column="householder" jdbcType="VARCHAR" property="sysuserinfo.householder" />
        <result column="marriage" jdbcType="VARCHAR" property="sysuserinfo.marriage" />
        <result column="msn" jdbcType="VARCHAR" property="sysuserinfo.msn" />
        <result column="nativity_address" jdbcType="VARCHAR" property="sysuserinfo.nativityAddress" />
        <result column="qq" jdbcType="VARCHAR" property="sysuserinfo.qq" />
        <result column="speciality" jdbcType="VARCHAR" property="sysuserinfo.speciality" />
        <result column="description" jdbcType="VARCHAR" property="sysuserinfo.description" />
        <result column="version" jdbcType="BIGINT" property="sysuserinfo.version" />
    </resultMap >

扩展方法来使用它

 <select id="selectextends" parameterType="java.lang.String" resultMap="UserinfoBaseResultExtMap">
        select
         u.id, username, password, name, sex, status, org_id, email, idcard, is_admin, sort,
        mobile,address, post_code, height, weight, birthday, blood, culture, finish_school_date,
        folk, government, homepage, householder, marriage, msn, nativity_address, qq, speciality,
        description, version
        from sys_user u LEFT OUTER JOIN sys_user_info ui ON  u.id=ui.id
           where username = #{username,jdbcType=VARCHAR}
    </select>

一对一映射

使用嵌套结果ResultMap实现一对一关系映射

在我们的域模型样例中，每一个用户都有一个与之关联的用户扩展信息。表sys_user有一个id列，是sys_user_info表的外键。我们定义一个resultMap中，sys_user_info的属性使用了圆点记法被赋上了对应列的值。

 <resultMap id="BaseResultExtMapext" type="com.goku.mybatis.model.sysUser">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="username" jdbcType="VARCHAR" property="username" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sex" jdbcType="VARCHAR" property="sex" />
        <result column="status" jdbcType="CHAR" property="status" />
        <result column="org_id" jdbcType="VARCHAR" property="orgId" />
        <result column="email" jdbcType="VARCHAR" property="email" />
        <result column="idcard" jdbcType="VARCHAR" property="idcard" />
        <result column="is_admin" jdbcType="VARCHAR" property="isAdmin" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="mobile" jdbcType="VARCHAR" property="mobile" />
        <result column="address" jdbcType="VARCHAR" property="sysuserinfo.address" />
        <result column="height" jdbcType="VARCHAR" property="sysuserinfo.height" />
        <result column="weight" jdbcType="VARCHAR" property="sysuserinfo.weight" />
        <result column="birthday" jdbcType="DATE" property="sysuserinfo.birthday" />
        <result column="blood" jdbcType="VARCHAR" property="sysuserinfo.blood" />
        <result column="culture" jdbcType="VARCHAR" property="sysuserinfo.culture" />
        <result column="finish_school_date" jdbcType="DATE" property="sysuserinfo.finishSchoolDate" />
        <result column="folk" jdbcType="VARCHAR" property="sysuserinfo.folk" />
        <result column="government" jdbcType="VARCHAR" property="sysuserinfo.government" />
        <result column="homepage" jdbcType="VARCHAR" property="sysuserinfo.homepage" />
        <result column="householder" jdbcType="VARCHAR" property="sysuserinfo.householder" />
        <result column="marriage" jdbcType="VARCHAR" property="sysuserinfo.marriage" />
        <result column="msn" jdbcType="VARCHAR" property="sysuserinfo.msn" />
        <result column="nativity_address" jdbcType="VARCHAR" property="sysuserinfo.nativityAddress" />
        <result column="qq" jdbcType="VARCHAR" property="sysuserinfo.qq" />
        <result column="speciality" jdbcType="VARCHAR" property="sysuserinfo.speciality" />
        <result column="description" jdbcType="VARCHAR" property="sysuserinfo.description" />
        <result column="version" jdbcType="BIGINT" property="sysuserinfo.version" />
    </resultMap >

扩展方法来使用它

    <select id="selectextends2" parameterType="java.lang.String" resultMap="BaseResultExtMapext">
        select
        u.id, username, password, name, sex, status, org_id, email, idcard, is_admin, sort,
        mobile,address, post_code, height, weight, birthday, blood, culture, finish_school_date,
        folk, government, homepage, householder, marriage, msn, nativity_address, qq, speciality,
        description, version
        from sys_user u LEFT OUTER JOIN sys_user_info ui ON  u.id=ui.id
        where username = #{username,jdbcType=VARCHAR}
    </select>

使用嵌套Select语句实现一对一关系映射

上述样例展示了一对一关联映射的一种方法。然而，使用这种方式映射，如果sysuserinfo结果需要在其他的SELECT映射语句中映射成Address对象，我们需要为每一个语句重复这种映射关系。MyBatis提供了更好地实现一对一关联映射的方法：嵌套结果ResultMap和嵌套select查询语句。

嵌套结果ResultMap

      <resultMap id="userinfoBaseResultMap" type="com.goku.mybatis.model.sysUserInfo">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="address" jdbcType="VARCHAR" property="address" />
        <result column="post_code" jdbcType="VARCHAR" property="postCode" />
        <result column="height" jdbcType="VARCHAR" property="height" />
        <result column="weight" jdbcType="VARCHAR" property="weight" />
        <result column="birthday" jdbcType="DATE" property="birthday" />
        <result column="blood" jdbcType="VARCHAR" property="blood" />
        <result column="culture" jdbcType="VARCHAR" property="culture" />
        <result column="finish_school_date" jdbcType="DATE" property="finishSchoolDate" />
        <result column="folk" jdbcType="VARCHAR" property="folk" />
        <result column="government" jdbcType="VARCHAR" property="government" />
        <result column="homepage" jdbcType="VARCHAR" property="homepage" />
        <result column="householder" jdbcType="VARCHAR" property="householder" />
        <result column="marriage" jdbcType="VARCHAR" property="marriage" />
        <result column="msn" jdbcType="VARCHAR" property="msn" />
        <result column="nativity_address" jdbcType="VARCHAR" property="nativityAddress" />
        <result column="qq" jdbcType="VARCHAR" property="qq" />
        <result column="speciality" jdbcType="VARCHAR" property="speciality" />
        <result column="description" jdbcType="VARCHAR" property="description" />
        <result column="version" jdbcType="BIGINT" property="version" />
    </resultMap>
  <resultMap type="com.goku.mybatis.model.sysUser" id="BaseResultExtMapext3">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="username" jdbcType="VARCHAR" property="username" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sex" jdbcType="VARCHAR" property="sex" />
        <result column="status" jdbcType="CHAR" property="status" />
        <result column="org_id" jdbcType="VARCHAR" property="orgId" />
        <result column="email" jdbcType="VARCHAR" property="email" />
        <result column="idcard" jdbcType="VARCHAR" property="idcard" />
        <result column="is_admin" jdbcType="VARCHAR" property="isAdmin" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="mobile" jdbcType="VARCHAR" property="mobile" />
        <association property="sysuserinfo" resultMap="userinfoBaseResultMap" />
    </resultMap>

相对应的扩展方法来使用它

    <select id="selectextends5" parameterType="java.lang.String" resultMap="BaseResultExtMapext3">
        select
        u.id, username, password, name, sex, status, org_id, email, idcard, is_admin, sort,
        mobile,address, post_code, height, weight, birthday, blood, culture, finish_school_date,
        folk, government, homepage, householder, marriage, msn, nativity_address, qq, speciality,
        description, version
        from sys_user u LEFT OUTER JOIN sys_user_info ui ON  u.id=ui.id
        where username = #{username,jdbcType=VARCHAR}
    </select>

元素<association>被用来导入“有一个”(has-one)类型的关联。在上述的例子中，我们使用了<association>元素引用了另外的在同一个XML文件中定义的<resultMap>。也可以使用<association>定义内联的resultMap。

<resultMap type="com.goku.mybatis.model.sysUser" id="BaseResultExtMapext4">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="username" jdbcType="VARCHAR" property="username" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sex" jdbcType="VARCHAR" property="sex" />
        <result column="status" jdbcType="CHAR" property="status" />
        <result column="org_id" jdbcType="VARCHAR" property="orgId" />
        <result column="email" jdbcType="VARCHAR" property="email" />
        <result column="idcard" jdbcType="VARCHAR" property="idcard" />
        <result column="is_admin" jdbcType="VARCHAR" property="isAdmin" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="mobile" jdbcType="VARCHAR" property="mobile" />
        <association property="sysuserinfo" javaType="com.goku.mybatis.model.sysUserInfo">
            <id column="id" jdbcType="VARCHAR" property="id" />
            <result column="address" jdbcType="VARCHAR" property="address" />
            <result column="post_code" jdbcType="VARCHAR" property="postCode" />
            <result column="height" jdbcType="VARCHAR" property="height" />
            <result column="weight" jdbcType="VARCHAR" property="weight" />
            <result column="birthday" jdbcType="DATE" property="birthday" />
            <result column="blood" jdbcType="VARCHAR" property="blood" />
            <result column="culture" jdbcType="VARCHAR" property="culture" />
            <result column="finish_school_date" jdbcType="DATE" property="finishSchoolDate" />
            <result column="folk" jdbcType="VARCHAR" property="folk" />
            <result column="government" jdbcType="VARCHAR" property="government" />
            <result column="homepage" jdbcType="VARCHAR" property="homepage" />
            <result column="householder" jdbcType="VARCHAR" property="householder" />
            <result column="marriage" jdbcType="VARCHAR" property="marriage" />
            <result column="msn" jdbcType="VARCHAR" property="msn" />
            <result column="nativity_address" jdbcType="VARCHAR" property="nativityAddress" />
            <result column="qq" jdbcType="VARCHAR" property="qq" />
            <result column="speciality" jdbcType="VARCHAR" property="speciality" />
            <result column="description" jdbcType="VARCHAR" property="description" />
            <result column="version" jdbcType="BIGINT" property="version" />
        </association>
    </resultMap>

嵌套select查询语句

    <resultMap type="com.goku.mybatis.model.sysUser" id="BaseResultExtMapext2">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="username" jdbcType="VARCHAR" property="username" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sex" jdbcType="VARCHAR" property="sex" />
        <result column="status" jdbcType="CHAR" property="status" />
        <result column="org_id" jdbcType="VARCHAR" property="orgId" />
        <result column="email" jdbcType="VARCHAR" property="email" />
        <result column="idcard" jdbcType="VARCHAR" property="idcard" />
        <result column="is_admin" jdbcType="VARCHAR" property="isAdmin" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="mobile" jdbcType="VARCHAR" property="mobile" />
        <association property="sysuserinfo" column="id" select="findsysUserInfoById"/>
    </resultMap>

相对应的扩展方法来使用它

    <select id="findsysUserInfoById" parameterType="String"
            resultMap="userinfoBaseResultMap">
        SELECT * FROM  sys_user_info where id = #{id,jdbcType=VARCHAR}
    </select>
    <select id="selectextends4" parameterType="java.lang.String" resultMap="BaseResultExtMapext2">
        select *  from sys_user  where username = #{username,jdbcType=VARCHAR}
    </select>

一对多映射

我们创建一张机构表一个机构包含多个用户。在sys_org中增加sys_user对象。

    public List<sysUser> getSysuser() {
        return sysuser;
    }

    public void setSysuser(List<sysUser> sysuser) {
        this.sysuser = sysuser;
    }

    private  List<sysUser> sysuser;

使用内嵌结果ResultMap实现一对多映射

    <resultMap id="OrgBaseResultMapext1" type="com.goku.mybatis.model.sysOrg">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="version" jdbcType="BIGINT" property="version" />
        <result column="level" jdbcType="BIGINT" property="level" />
        <result column="type" jdbcType="CHAR" property="type" />
        <result column="description" jdbcType="VARCHAR" property="description" />
        <result column="image" jdbcType="VARCHAR" property="image" />
        <result column="isparent" jdbcType="VARCHAR" property="isparent" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="url" jdbcType="VARCHAR" property="url" />
        <result column="parent_id" jdbcType="VARCHAR" property="parentId" />
        <result column="operate" jdbcType="VARCHAR" property="operate" />
        <collection  property="sysuser" resultMap="userBaseResultMap" />
    </resultMap>

相对应的扩展方法来使用它

    <select id="selectextend1" parameterType="java.lang.String" resultMap="OrgBaseResultMapext1">
            select   o.id, version, level, type, description, image, isparent, o.name, o.sort, url, parent_id,
             u.id as uid, username, password, u.name, sex, status, org_id, email, idcard, is_admin, u.sort,
                mobile from sys_org o LEFT OUTER JOIN sys_user u
            on o.id=u.org_id where o.id = #{id,jdbcType=VARCHAR}
    </select>

级联查询的时候，主表和从表有一样的字段名的时候，在mysql上命令查询是没问题的。但在mybatis中主从表需要为相同字段名设置别名。

<collection>元素被用来将多行结果映射成一个对象的一个集合。

使用嵌套Select语句实现一对多映射

 <resultMap id="OrgBaseResultMapext2" type="com.goku.mybatis.model.sysOrg">
        <!--
          WARNING - @mbg.generated
          This element is automatically generated by MyBatis Generator, do not modify.
        -->
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="version" jdbcType="BIGINT" property="version" />
        <result column="level" jdbcType="BIGINT" property="level" />
        <result column="type" jdbcType="CHAR" property="type" />
        <result column="description" jdbcType="VARCHAR" property="description" />
        <result column="image" jdbcType="VARCHAR" property="image" />
        <result column="isparent" jdbcType="VARCHAR" property="isparent" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="sort" jdbcType="BIGINT" property="sort" />
        <result column="url" jdbcType="VARCHAR" property="url" />
        <result column="parent_id" jdbcType="VARCHAR" property="parentId" />
        <result column="operate" jdbcType="VARCHAR" property="operate" />
        <collection  property="sysuser" column="id" select="findsysUserByOrgId"  />
    </resultMap>

相对应的扩展方法来使用它

    <select id="findsysUserByOrgId" parameterType="String"
            resultMap="userBaseResultMap">
        SELECT * FROM  sys_user where org_id = #{id,jdbcType=VARCHAR}
    </select>
    <select id="selectextend2" parameterType="java.lang.String" resultMap="OrgBaseResultMapext2">
        select * from sys_org where id = #{id,jdbcType=VARCHAR}
    </select>

GITHUB

github :  https://github.com/nbfujx/learn-java-demo/tree/master/Goku.MybatisDemo.XML