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>
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