#yyds干货盘点# mybatis的foreach的3种使用方法

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：

<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());
        }
    }
}