详解mybatis中的if-else的嵌套使用
作者：舒克日记
本文主要介绍了mybatis中的if-else的嵌套使用，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧
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>
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