模糊查询

$

这种方式，简单，但是无法防止SQL注入，所以不推荐使用

 LIKE  '%${name}%'

#

 LIKE "%"#{name}"%"

字符串拼接

AND name LIKE CONCAT(CONCAT('%',#{name},'%'))

bind标签

<select id="searchStudents" resultType="com.example.entity.StudentEntity"
  parameterType="com.example.entity.StudentEntity">
  <bind name="pattern1" value="'%' + _parameter.name + '%'" />
  <bind name="pattern2" value="'%' + _parameter.address + '%'" />
  SELECT * FROM test_student
  <where>
   <if test="age != null and age != '' and compare != null and compare != ''">
    age
    ${compare}
    #{age}
   </if>
   <if test="name != null and name != ''">
    AND name LIKE #{pattern1}
   </if>
   <if test="address != null and address != ''">
    AND address LIKE #{pattern2}
   </if>
  </where>
  ORDER BY id
 </select>

java代码里写

param.setUsername("%CD%"); 在 java 代码中传参的时候直接写上

 <if test="username!=null"> AND username LIKE #{username}</if>

然后 mapper 里面直接写 #{} 就可以了