MyBatis动态sql

Mybatis是我们现在常用的一个框架，他的功能非常强大尤其是动态sql，我偶尔看到一篇帖子针对Mybatis动态sql的使用介绍的非常详细，所以给大家分享出来。
相关链接
[1]: https://mp.weixin.qq.com/s?__biz=MzIwMzY1OTU1NQ==&mid=2247493491&idx=1&sn=d83791e6bd0a093c83851010c00a75f7&chksm=96cea73fa1b92e29bd46dedcdadbdcf85d7c6d838d826aca7d72f99dbde37afe134ed8436cef&mpshare=1&scene=23&srcid=0801Lf2ZaJJlSCUi8MWjYIGc&sharer_sharetime=1597573639081&sharer_shareid=e503c766ca289af74ab1826a7f43b366%23rd

Mybatis各种入参以及返回值相关描述

案例1，当入参是list时在xml中的parameterType可以不写，而resultType则写集合的泛型类型即可 代码片.

// dao
User getUsersById(@Param("idls") List<String> idls);

// xml
<select id="getUsersById" resultType="com.beiyun.lcm.entity.User">
		select auto_id as autoId,name as name ,age as age
		 from user
		where id in 
		<foreach collection="idls"  item="item"  open="(" separator="," close=")">
			#{
     item}
		</foreach>
</select>

案例2，当入参是map 代码片.

// java
Map<String,String> map =  new HashMap<> ();
map.put("userName","张三")；
map.put("age","100");
this.userMapper.getUserByMap(map);

// dao
User getUserByMap(@Param("map") Map<String,Object> map);

// xml
<select id="getUsersById" resultType="com.beiyun.lcm.entity.User">
		select auto_id as autoId,name as name ,age as age
		 from user
		where name = #{
     userName} and age =#{
     age}
</select>

案例3，当入参是array 代码片.

// dao
List<User> getUserls(@Param("ids") Integer[] ids);

// xml
<select id="getUserls" resultType="com.beiyun.lcm.entity.User">
		select auto_id as autoId,name as name ,age as age
		 from user
		where id in 
		<foreach index="index" collection="array"  item="item"  open="(" separator="," close=")">
			#{
     item}
		</foreach>
</select>

案例3，当入参是字符串或者实体 代码片.

// dao
List<User> getUserByName(@Param("name") String name);

// xml
<select id="getUserByName" resultType="com.beiyun.lcm.entity.User">
		select auto_id as autoId,name as name ,age as age
		 from user
		where name concat（“%”，name，“%”）
</select>

// dao
List<User> getUserList(User user);

// xml
<select id="getUserList" resultType="com.beiyun.lcm.entity.User">
		select auto_id as autoId,name as name ,age as age
		 from user
		 // 直接用实体中的属性即可
		where name concat（“%”，name，“%”）,age =#{
     age}
</select>

***当返回值值是一个集合时，resultType只要写泛型类型即可，mybatis会根据实际的查询结果进行映射处理。