MyBatis-parameterType 取出入参值

SQL 映射文件的几种入参情况

一、单个基本类型参数

public MyUser selectMyUser(Integer id);

<!-- #{参数名或任意名}：取出参数值 -->
<select id="selectMyUser" resultType="myUser" parameterType="integer">
  select * from myuser where id = #{id}
</select>

二、多个基本类型参数

多个参数会被封装成 一个Map，Key 为 param1...paramN，或者参数的索引 (0开始)：arg0...argN，Value 为传入的参数值

public MyUser selectMyUserIdAndAge(Integer id,Integer age);

<!-- #{arg0}/#{param1}：取出参数值 -->
<select id="selectMyUserIdAndAge" resultType="myUser">
  select * from myuser where id = #{param1} and age = #{arg1}
</select>

使用 @Param 注解

public MyUser selectMyUserIdAndAge(@Param("id") Integer id, @Param("age") Integer age);

<!-- #{@Param标识值}：取出参数值 -->
<select id="selectMyUserIdAndAge" resultType="myUser">
  select * from myuser where id = #{id} and age = #{age}
</select>

封装成 Map 对象

public MyUser selectMyUserIdAndAgeOfMap(Map<String,Object> map);

<!-- #{key}：取出map中对应的值 -->
<select id="selectMyUserIdAndAgeOfMap" resultType="myUser">
  select * from myuser where id = #{id} and age = #{age}
</select>

封装成一个类，例直接使用 POJO 对象

public Integer updateMyUser(MyUser user);

<!-- #{属性名}：取出传入pojo的属性值 -->
<update id="updateMyUser" parameterType="myUser">
    update myuser set name=#{name},age=#{age} where id=#{id}
</update>

三、Collection 集合类型

public MyUser selectMyUserByList(List<Integer> ids);

<!-- #{collection[0]}：取出参数值,若为 List 还可使用 #{list[0]} -->
<select id="selectMyUserByList" resultType="myUser">
  select * from myuser where id = #{list[0]}
</select>

四、Array 数组类型

public MyUser selectMyUserByArray(Integer[] integers);

<!-- #{array[0]}：取出参数值 -->
<select id="selectMyUserByArray" resultType="myUser">
  select * from myuser where id = #{array[0]}
</select>

五、多种参数类型

public MyUser selectMyUserIdAndAge(Integer id, @Param("user") MyUser user);

<select id="selectMyUserIdAndAge" resultType="myUser">
  select * from myuser where id = #{arg0} and age = #{user.age}
</select>

附上 MyBatis 封装集合的方法

org.apache.ibatis.session.defaults.DefaultSqlSession

public class DefaultSqlSession implements SqlSession {

    private Object wrapCollection(final Object object) {
        if (object instanceof Collection) {
            StrictMap<Object> map = new StrictMap<>();
            map.put("collection", object);
            if (object instanceof List) {
                map.put("list", object);
            }
            return map;
        } else if (object != null && object.getClass().isArray()) {
            StrictMap<Object> map = new StrictMap<>();
            map.put("array", object);
            return map;
        }
        return object;
    }

---

如果传入的是 Collection（List、Set）集合类型或者是 Array 数组类型，会把传入的 Collection 集合或者 Array 数组封装在 Map 中。