MyBatis-条件子句中的嵌套条件

问题描述

我正在MyBatis v3映射器xml中动态生成where子句.但是，放置括号确实很麻烦.有没有不使用if语句就可以解决问题的简便方法?

I'm dynamically generating the where clause inside MyBatis v3 mapper xml. However placing parentheses is really cumbersome. Is there an easier way to handle the problem without using if statements?

<where>
  <if test="filter != null">
    <choose>
      <when test="filter.lref != null">
        file.lref = #{filter.lref}
      </when>
      <otherwise>
        <!-- I don't want to use this -->
        <if test="filter.forLike != null || filter.forInt != null">
          (
        </if>
        <if test="filter.forLike != null" >
          subject LIKE #{filter.forLike}
          OR requester_identifier LIKE #{filter.forLike}
          OR requester_name LIKE #{filter.forLike}
        </if>
        <if test="filter.forInt != null">
          OR file_id = #{filter.forInt}
        </if>

        <!-- I don't want to use this -->
        <if test="filter.forLike != null || filter.forInt != null">
          )
        </if>
      </otherwise>
    </choose>
  </if>
  <if test="listMode > 0">
    <choose>
       <when test="listMode == 1">
         AND file_status_link.dosya_ref is not NULL
       </when>
       <otherwise>
         AND file_status_link.dosya_ref is NULL
       </otherwise>
    </choose>
   </if>
</where>

动态生成的SQL输出示例如下

Sample dynamically generated SQL output is as follows

WHERE ( subject LIKE ? OR requester_identifier LIKE ? OR requester_name LIKE ? )
AND file_status_link.dosya_ref is NULL

推荐答案

您可以尝试将该部分封装在<trim>标记内.会是这样的:

You can try to encapsulate that part inside <trim> tag. It would be something like this:

<trim prefix="(" prefixOverrides="OR" suffix=")">
  <if test="filter.forLike != null" >
    subject LIKE #{filter.forLike}
    OR requester_identifier LIKE #{filter.forLike}
    OR requester_name LIKE #{filter.forLike}
  </if>
  <if test="filter.forInt != null">
    OR file_id = #{filter.forInt}
  </if>
</trim>

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