Mybatis级联，使用JOIN和Associa,以及一些ID覆盖和自动变换。

先说下坑，比如数据库的字段是 DW_ID  ，用generator讲mybatis自动转换的时候，会省略下表_变成dwId，所以我们之后自己手动设计的时候也尽量换成dwId；

generate的mybatis不是重新生成而是覆盖原来文字

Mybatis的级联

<resultMap id="BaseResultMap" type="com.ylzinfo.apps.rsdl.domain.RSDL_SHXX">
<id column="ID" jdbcType="VARCHAR" property="id" />
<result column="DW_ID" jdbcType="VARCHAR" property="dwId" />
<result column="DY_TYPE" jdbcType="VARCHAR" property="dyType" />
<result column="DWNAME" jdbcType="VARCHAR" property="dwname" />
<result column="ZJHM" jdbcType="VARCHAR" property="zjhm" />
<result column="SBSJ" jdbcType="VARCHAR" property="sbsj" />
<result column="YDLJG_ID" jdbcType="VARCHAR" property="ydljgId" />
<result column="YDLSTATE" jdbcType="VARCHAR" property="ydlstate" />
<result column="YDLOPNION" jdbcType="VARCHAR" property="ydlopnion" />
<result column="XDLJG_ID" jdbcType="VARCHAR" property="xdljgId" />
<result column="XDLSTATE" jdbcType="VARCHAR" property="xdlstate" />
<result column="XDLOPNION" jdbcType="VARCHAR" property="xdlopnion" />
<result column="JYSTATE" jdbcType="VARCHAR" property="jystate" />
<result column="JYREASON" jdbcType="VARCHAR" property="jyreason" />
<result column="JYOPNION" jdbcType="VARCHAR" property="jyopnion" />
<result column="SCSQ" jdbcType="VARCHAR" property="scsq" />
<result column="YLZD1" jdbcType="VARCHAR" property="ylzd1" />
<result column="YLZD2" jdbcType="VARCHAR" property="ylzd2" />
<result column="YLZD3" jdbcType="VARCHAR" property="ylzd3" />
<result column="YLZD4" jdbcType="VARCHAR" property="ylzd4" />
<result column="YLZD5" jdbcType="VARCHAR" property="ylzd5" />
<result column="SYS_CREATE_TIME" jdbcType="VARCHAR" property="sysCreateTime" />
<result column="SYS_CREATE_USER" jdbcType="VARCHAR" property="sysCreateUser" />
<result column="SYS_UPDATE_TIME" jdbcType="VARCHAR" property="sysUpdateTime" />
<result column="SYS_UPDATE_USER" jdbcType="VARCHAR" property="sysUpdateUser" />
<association column="YDLJG_ID" select="getYdwjg" property="ydwjg"/>
<association column="XDLJG_ID" select="getXdwjg" property="xdwjg"/>

<result column="SYS_CREATE_USER" jdbcType="VARCHAR" property="sysCreateUser" />
    <result column="SYS_UPDATE_TIME" jdbcType="VARCHAR" property="sysUpdateTime" />
    <result column="SYS_UPDATE_USER" jdbcType="VARCHAR" property="sysUpdateUser" />
    <association column="YDLJG_ID" select="getYdwjg"  property="ydwjg"/>
  </resultMap>
  <sql id="Base_Column_List">
    ID, DW_ID, DY_TYPE, DWNAME, ZJHM, SBSJ, YDLJG_ID, YDLSTATE, YDLOPNION, XDLJG_ID,
    XDLSTATE, XDLOPNION, JYSTATE, JYREASON, JYOPNION, SCSQ, YLZD1, YLZD2, YLZD3, YLZD4,
    YLZD5, SYS_CREATE_TIME, SYS_CREATE_USER, SYS_UPDATE_TIME, SYS_UPDATE_USER
  </sql>
  <select id="selectByPrimaryKey" parameterType="java.lang.String" resultMap="BaseResultMap">
    select
    <include refid="Base_Column_List" />
    from RSDL_SHXX
    where ID = #{id,jdbcType=VARCHAR}
  </select>
  <select id="getYdwjg" parameterType="java.lang.String" resultType="com.ylzinfo.apps.unit.domain.UnitBaseInfo">
        SELECT  NAME FROM Unit_Baseinfo WHERE id=#{ydwjg,jdbcType=VARCHAR}
      </select>

  <select id="selectByDwId" parameterType="java.lang.String" resultMap="BaseResultMap">
    select
    <include refid="Base_Column_List" />
    from RSDL_SHXX
    where DW_ID = #{dwId,jdbcType=VARCHAR}
  </select>

里面是级联部分代码，其中resultMap用来映射实体类对应的字段，用于返回数据，其中如果原本的实体类里面又包含实体类，我们就可以使用级联。在resultMap里面跟上级联实体类的名字，后面加入方法，

之后专门添加对应的select进行级联。

因为上个方法在项目中不知道为什么原因，如果名字一样就只能显示一个名字，而且如果只是要名字的话却封装一个对象，有点大材小用，故用到JOIN 来替换。

<select id="queryAndName" parameterType="java.lang.String"
        resultMap="BaseResultMap2">
        select r.id as ID,
        r.dw_id as DW_ID,
        r.dwname as DWNAME,
        r.zjhm as ZJHM,
        r.sbsj as SBSJ,
        r.ydljg_id as YDLJG_ID,
        r.ydlstate as YDLSTATE,
        r.xdljg_id as XDLJG_ID,
        r.xdlstate as XDLSTATE,
        r.ylzd1 as YLZD1,
        u1.dwname as YDLJG_NAME,
        u2.dwname as XDLJG_NAME
        from RSDL_SHXX r
        left outer join RSDL_DLJG u1 on r.ydljg_id = u1.dwid
        left outer join RSDL_DLJG u2 on r.xdljg_id = u2.dwid
        where 1=1
        <if test="dwId != null and dwId != ''">
            and DW_ID like CONCAT(CONCAT('%',#{dwId}),'%')
        </if>
        <if test="dyType != null and dyType != ''">
            and DY_TYPE like CONCAT(CONCAT('%',#{dyType}),'%')
        </if>
        <if test="dwname != null and dwname != ''">
            and DWNAME like CONCAT(CONCAT('%',#{dwname}),'%')
        </if>
        <if test="zjhm != null and zjhm != ''">
            and ZJHM like CONCAT(CONCAT('%',#{zjhm}),'%')
        </if>
        <if test="sbsj != null and sbsj != ''">
            and SBSJ like CONCAT(CONCAT('%',#{sbsj}),'%')
        </if>
        <if test="ydljgId != null and ydljgId != ''">
            and YDLJG_ID like CONCAT(CONCAT('%',#{ydljgId}),'%')
        </if>
        <if test="ydlstate != null and ydlstate != ''">
            and YDLSTATE like CONCAT(CONCAT('%',#{ydlstate}),'%')
        </if>
        <if test="ydlopnion != null and ydlopnion != ''">
            and YDLOPNION like CONCAT(CONCAT('%',#{ydlopnion}),'%')
        </if>
        <if test="xdljgId != null and xdljgId != ''">
            and XDLJG_ID like CONCAT(CONCAT('%',#{xdljgId}),'%')
        </if>
        <if test="xdlstate != null and xdlstate != ''">
            and XDLSTATE like CONCAT(CONCAT('%',#{xdlstate}),'%')
        </if>
        <if test="ydlopnion != null and ydlopnion != ''">
            and XDLOPNION like CONCAT(CONCAT('%',#{ydlopnion}),'%')
        </if>
        <if test="jystate != null and jystate != ''">
            and JYSTATE like CONCAT(CONCAT('%',#{jystate}),'%')
        </if>
        <if test="jyreason != null and jyreason != ''">
            and JYREASON like CONCAT(CONCAT('%',#{jyreason}),'%')
        </if>
        <if test="jyopnion != null and jyopnion != ''">
            and JYOPNION like CONCAT(CONCAT('%',#{jyopnion}),'%')
        </if>
        <if test="ylzd1 != null and ylzd1 != ''">
            and YLZD1 like CONCAT(CONCAT('%',#{ylzd1}),'%')
        </if>
        <if test="ylzd2 != null and ylzd2 != ''">
            and YLZD2 like CONCAT(CONCAT('%',#{ylzd2}),'%')
        </if>
        <if test="ylzd3 != null and ylzd3 != ''">
            and YLZD3 like CONCAT(CONCAT('%',#{ylzd3}),'%')
        </if>
        <if test="ylzd4 != null and ylzd4 != ''">
            and YLZD4 like CONCAT(CONCAT('%',#{ylzd4}),'%')
        </if>
        <if test="ylzd5 != null and ylzd5 != ''">
            and YLZD5 like CONCAT(CONCAT('%',#{ylzd5}),'%')
        </if>
        order by r.sbsj desc
        <!-- select <include refid="Base_Column_List" /> from RSDL_SHXX where DW_ID
            = #{dwId,jdbcType=VARCHAR} order by sbsj desc -->
    </select>

resultmap和java实体类

<resultMap id="BaseResultMap2" type="com.ylzinfo.apps.rsdl.domain.RSDL_SHXX">
        <id column="ID" jdbcType="VARCHAR" property="id" />
        <result column="DW_ID" jdbcType="VARCHAR" property="dwId" />
        <result column="DY_TYPE" jdbcType="VARCHAR" property="dyType" />
        <result column="DWNAME" jdbcType="VARCHAR" property="dwname" />
        <result column="ZJHM" jdbcType="VARCHAR" property="zjhm" />
        <result column="SBSJ" jdbcType="VARCHAR" property="sbsj" />
        <result column="YDLJG_ID" jdbcType="VARCHAR" property="ydljgId" />
        <result column="YDLSTATE" jdbcType="VARCHAR" property="ydlstate" />
        <result column="YDLOPNION" jdbcType="VARCHAR" property="ydlopnion" />
        <result column="XDLJG_ID" jdbcType="VARCHAR" property="xdljgId" />
        <result column="XDLSTATE" jdbcType="VARCHAR" property="xdlstate" />
        <result column="XDLOPNION" jdbcType="VARCHAR" property="xdlopnion" />
        <result column="JYSTATE" jdbcType="VARCHAR" property="jystate" />
        <result column="JYREASON" jdbcType="VARCHAR" property="jyreason" />
        <result column="JYOPNION" jdbcType="VARCHAR" property="jyopnion" />
        <result column="SCSQ" jdbcType="VARCHAR" property="scsq" />
        <result column="YLZD1" jdbcType="VARCHAR" property="ylzd1" />
        <result column="YLZD2" jdbcType="VARCHAR" property="ylzd2" />
        <result column="YLZD3" jdbcType="VARCHAR" property="ylzd3" />
        <result column="YLZD4" jdbcType="VARCHAR" property="ylzd4" />
        <result column="YLZD5" jdbcType="VARCHAR" property="ylzd5" />
        <result column="SYS_CREATE_TIME" jdbcType="VARCHAR" property="sysCreateTime" />
        <result column="SYS_CREATE_USER" jdbcType="VARCHAR" property="sysCreateUser" />
        <result column="SYS_UPDATE_TIME" jdbcType="VARCHAR" property="sysUpdateTime" />
        <result column="SYS_UPDATE_USER" jdbcType="VARCHAR" property="sysUpdateUser" />
        <result column="YDLJG_NAME" jdbcType="VARCHAR" property="ydwjg" />
        <result column="XDLJG_NAME" jdbcType="VARCHAR" property="xdwjg" />
    </resultMap>

 /**
     * 创建时间，一旦创建无法改变。
     */
    private String sysCreateTime;

    /**
     * 创建用户，一旦创建无法改变。
     */
    private String sysCreateUser;

    /**
     * 更改时间
     */
    private String sysUpdateTime;

    /**
     * 更改用户
     */
    private String sysUpdateUser;

    /**
     * 原单位机构，用来取名字。
     */
    private String ydwjg;

    /**
     * 新单位机构，用来取名字。
     */
    private String xdwjg;