mapper.xml-if应用场景: curd-传参判空和集合判断元素个数

mapper.java

 int deleteRelationsByRoleids(@Param("roleIds") Integer[] roleIds);

mapper.xml

 <delete id="deleteRelationsByRoleids">
        DELETE FROM user_role
        WHERE 1==1 
          <if test="null != roleIds and roleIds.size() > 0" >
               and role_id in
        <foreach collection="roleIds" item="item" index="index" open="(" separator="," close=")">
            #{item,jdbcType=INTEGER}
        </foreach>
           </if>
    </delete>