详解mybatis中的if-else的嵌套使用

目录

• 案例一：if-else
• 案例二：if嵌套
• MyBatis中if和choose的嵌套

案例一：if-else

在mybatis的使用过程中，难免会存在使用if-else的逻辑，但是实际是没有这种语法的，提供了choose标签来替代这种语法

   <select id="selectUserByState" resultType="com.bz.model.entity.User">
    SELECT
      *
    FROM
      user
    WHERE
      1=1
    <choose>
      <when test="state == 1">
        AND name = #{name1}
      </when>
     <when test="state == 2">
        AND name = #{name2}
      </when>
      <otherwise>
        AND name = #{name3}
      </otherwise>
    </choose>
  </select>

案例二：if嵌套

在实际的编码过程中会对一些条件进行重复判断，并对内深入if判断，这时就可以使用if嵌套

  <select id="selectUserByState" resultType="com.bz.model.entity.User">
    SELECT
      *
    FROM
      user
    WHERE
     <if test=" gender!=null and gender!='' ">
         <if test=" gender==male ">
             and name=#{name}
         </if>
     </if>
  </select>

MyBatis中if和choose的嵌套

    <!-- public List<VadtaxShow> findList(VadtaxShow vadtaxShow); -->
    <select id="findList" parameterType="com.cdqyzj_WC.Backstage.vaddedtax.domain.VaddeTax" resultType="com.cdqyzj_WC.Backstage.vaddedtax.domain.VaddeTax">
    SELECT t.addedId,t.taxType,t.totalSales,t.outputTax,t.inputTax,t.entryAmount, t.amountTax,t.retentionTax,
    t.createTime, t.taxTime,t.comId,c.comName,c.comType
    FROM t_g_vaddedtax AS t JOIN t_ucompany AS c ON c.comId = t.comId
    <where>
    1=1
            <if test="comType != '' and comType != null"> and c.comType = #{comType}</if>
            <if test="taxTime != null and taxTime != ''"> and t.taxTime =#{taxTime} </if>
            <if test="taxType != null and taxType != '' "> and t.taxType =#{taxType} </if>
            <if test="comId != null and comId != '' and comId != 0 "> and t.comId =#{comId} </if>
            <if test="start_times != null and end_times != null">
                <choose>
                    <when test="middle_times != null">
                        and t.createTime in ('${start_times}','${middle_times}', '${end_times}' )
                    </when>
                    <otherwise>
                        and t.createTime in ('${start_times}','${end_times}' )
                    </otherwise>
                </choose>
            </if>
            <if test="orderBy != null and orderType != '' ">
                     order by ${orderBy}  ${orderType}
            </if>
            <if test="pageSize != 0 ">
                    limit ${startRows},${pageSize}
            </if>
    </where>
    </select>

功能实现之后反思：要不我不对“middle_times”判空？这样不就不用嵌套了吗？

    <!-- public List<VadtaxShow> findList(VadtaxShow vadtaxShow); -->
    <select id="findList" parameterType="com.cdqyzj_WC.Backstage.vaddedtax.domain.VaddeTax" resultType="com.cdqyzj_WC.Backstage.vaddedtax.domain.VaddeTax">
    SELECT t.addedId,t.taxType,t.totalSales,t.outputTax,t.inputTax,t.entryAmount, t.amountTax,t.retentionTax,
    t.createTime, t.taxTime,t.comId,c.comName,c.comType
    FROM t_g_vaddedtax AS t JOIN t_ucompany AS c ON c.comId = t.comId
    <where>
    1=1
            <if test="comType != '' and comType != null"> and c.comType = #{comType}</if>
            <if test="taxTime != null and taxTime != ''"> and t.taxTime =#{taxTime} </if>
            <if test="taxType != null and taxType != '' "> and t.taxType =#{taxType} </if>
            <if test="comId != null and comId != '' and comId != 0 "> and t.comId =#{comId} </if>
            <if test="start_times != null and end_times != null">
                and t.createTime in ('${start_times}','${middle_times}', '${end_times}' )
            </if>
            <if test="orderBy != null and orderType != '' ">
                     order by ${orderBy}  ${orderType}
            </if>
            <if test="pageSize != 0 ">
                    limit ${startRows},${pageSize}
            </if>
    </where>
    </select>

到此这篇关于详解mybatis中的if-else的嵌套使用的文章就介绍到这了,更多相关mybatis if-else嵌套内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！