mybatis的foreach的3种使用方法

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：

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

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

ListselectUserArr(int []arr);

ListuserArray=userMapper.selectUserArr(arr);

list的写法：

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

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

ListselectUserList(List list1);

ListuserList=userMapper.selectUserList(list1);

map的写法：

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

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

ListselectUserMap(Map map);

map.put("map1",map1);

List 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,Object> map=new HashMap, 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);
        ListuserArray=userMapper.selectUserArr(arr);
        ListuserList=userMapper.selectUserList(list1);
        List 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 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}

我的座右铭：不会，我可以学；落后，我可以追赶；跌倒，我可以站起来；我一定行。