MyBatis - Nested Conditions in Where Clause

问题

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>

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

回答1:

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>

回答2:

Pseudo-SQL (XML-SQL):

where
    1 = 1
    <A>and file.lref = #{filter.lref}</A>
    <D>and (
        <E>
        subject like #{filter.forLike}    
        or requester_identifier like #{filter.forLike}
        or requester_name like #{filter.forLike}
        </E>
        <F>or file_id = #{filter.forInt}</F>
    )</D>
    </B>
    <C>and file_status_link.dosya_ref is <G>not</G> null</C>

Where:

A: <B> && filter.lref != null
B: filter != null
D: <B> && (<E> || <F>)
E: filter.forLike != null
F: filter.forInt != null
C: listMode > 0
G: listMode == 1

来源：https://stackoverflow.com/questions/14306949/mybatis-nested-conditions-in-where-clause

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