mybatis的foreach的3种使用方法

朴灿烈づ我的快乐病毒、 2022-05-24 01:43 99阅读 0赞

### 用mybatis实现select 字段 from table where id in(1,2,3,4,5)的sql语句: ###

#### mybatis提供的foreach可以实现，foreach有3种传值方式：array，list,map. ####

#### 其中Array的mapper写法： ####

<select id="selectUserArr" resultMap="BaseResultMap">
        SELECT
        <include refid="Base_Column_List" />
        from user
        where id in
        <foreach collection="array" item="id" open="(" separator="," close=")">
            #{id}
        </foreach>
    </select>

#### 注：array的写法中collection中的值必须是array,不能写Array，会报错的。但传参的命名可以不是array    ####

List<User>selectUserArr(int []arr);

List<User>userArray=userMapper.selectUserArr(arr);

#### list的写法： ####

<select id="selectUserList" resultMap="BaseResultMap">
        SELECT
        <include refid="Base_Column_List" />
        from user
        where id in
        <foreach collection="list" item="id" open="(" separator="," close=")">
            #{id}
        </foreach>
    </select>

### 注：list写法中collection中的值必须是list,也不能是List,但传来的参数命名可以不一定是list ###

List<User>selectUserList(List list1);

List<User>userList=userMapper.selectUserList(list1);

#### map的写法： ####

<select id="selectUserMap" resultMap="BaseResultMap">
        SELECT
        <include refid="Base_Column_List" />
        from user
        where id in
        <foreach collection="map1" item="id" open="(" separator="," close=")">
            #{id}
        </foreach>
    </select>

### 注：map写法中的collection中填的是map的key值，不对应就会报错 ###

List<User>selectUserMap(Map map);

map.put("map1",map1);

List<User> userMap=userMapper.selectUserMap(map);

### 在springboot的启动类测试： ###

@SpringBootApplication
    @MapperScan("springboot.mapper")
    public class Application
    {
        public static void main( String[] args )
        {
            ApplicationContext context  = SpringApplication.run(Application.class, args);
           
            UserMapper userMapper=context.getBean(UserMapper.class);
    
            int []arr=new int[5];
            List list1=new ArrayList();
            Map<String,Object> map=new HashMap<String, Object>(5);
            int i;
            for(i=1;i<5;i++){
                arr[i-1]=i;
                list1.add(i);
    
            }
            int []map1={
      1,2,3,4,5};
            map.put("map1",map1);
            List<User>userArray=userMapper.selectUserArr(arr);
            List<User>userList=userMapper.selectUserList(list1);
            List<User> userMap=userMapper.selectUserMap(map);
    
            System.out.println("Array=============");
            sys(userArray);
            System.out.println("list=============");
            sys(userList);
            System.out.println("map:================");
            sys(userMap);
    
        public static void sys(List<User> list){
            for (User user : list){
                System.out.println("user:"+user.toString());
            }
        }
    }

效果如下：

Array=============
            user:User{id=1, uname='小黑', upwd='123', unum='123', sex=0, age=18, addr='广东', tid=1}
            user:User{id=2, uname='小白', upwd='234', unum='234', sex=1, age=21, addr='广州', tid=1}
            user:User{id=3, uname='小红', upwd='345', unum='345', sex=0, age=15, addr='天河区', tid=2}
            user:User{id=4, uname='小小', upwd='123', unum='567', sex=1, age=21, addr='null', tid=3}
            list=============
            user:User{id=1, uname='小黑', upwd='123', unum='123', sex=0, age=18, addr='广东', tid=1}
            user:User{id=2, uname='小白', upwd='234', unum='234', sex=1, age=21, addr='广州', tid=1}
            user:User{id=3, uname='小红', upwd='345', unum='345', sex=0, age=15, addr='天河区', tid=2}
            user:User{id=4, uname='小小', upwd='123', unum='567', sex=1, age=21, addr='null', tid=3}
            map:================
            user:User{id=1, uname='小黑', upwd='123', unum='123', sex=0, age=18, addr='广东', tid=1}
            user:User{id=2, uname='小白', upwd='234', unum='234', sex=1, age=21, addr='广州', tid=1}
            user:User{id=3, uname='小红', upwd='345', unum='345', sex=0, age=15, addr='天河区', tid=2}
            user:User{id=4, uname='小小', upwd='123', unum='567', sex=1, age=21, addr='null', tid=3}
            user:User{id=5, uname='柘城', upwd='123', unum='423', sex=0, age=23, addr='null', tid=2}

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