Question

上下文

我正在尝试使用SpringBoot，Hateeoas创建一个API，将数据存储到H2数据库中并通过JPA对其进行管理。

我有2个实体：Mission和User。

几个用户被分配了一个任务。并且可以将用户分配给不同的任务。

我使用@ManyToMany批注创建关联表。

目标

我的目标是创建一些请求：

（获取请求）IP/missions/123456/users：获取分配给任务123456的所有用户
（PUT请求）IP/missions/456789：已分配用户到任务456789

代码

实体

@Entity
public class Mission {

    @Id
    private String missionid;
    private String missionname;
    private Date start;
    private Date end;
    @ManyToMany(mappedBy = "missions")
    @JoinTable(name = "missions_users",
        joinColumns = @JoinColumn(name = "missionid"),
        inverseJoinColumns = @JoinColumn(name = "userid")
    )
    private Set<User> users = new HashSet<>();
    private int status;

    public Mission() {
    }

    public Mission(String name, Date start, Date end) {
        this.namemission = name;
        this.start = start;
        this.end = end;
        this.status = 0;
    }


}

@Entity
public class User {

    @Id
    private String userid;
    private String nameuser;
    @ManyToMany
    private Set<Mission> missions = new HashSet<>();

    public User() {
    }

    public User(String name) {
        this.nameuser = name;
    }
}

资源

@RepositoryRestResource(collectionResourceRel = "mission")
public interface MissionResource extends JpaRepository<Mission, String> {
}

@RepositoryRestResource(collectionResourceRel = "user")
public interface UserResource extends JpaRepository<User, String> {
}

RestController

@RestController
@RequestMapping(value = "/missions", produces = MediaType.APPLICATION_JSON_VALUE)
@ExposesResourceFor(Mission.class)
public class MissionRepresentation {

    private final MissionResource missionResource;
    private final UserResource userResource;

    public MissionRepresentation(MissionResource missionResource, UserResource userResource) {
        this.missionResource = missionResource;
        this.userResource = userResource;
    }

    // mapping
}

用于填充数据库的SQL脚本

INSERT INTO mission (missionid, namemission, start, end, status) VALUES ('de7d9052-4961-4b4f-938a-3cd12cbe1f82', 'mission 1', '2019-02-11', '2019-02-13', 0)
INSERT INTO mission (missionid, namemission, start, end, status) VALUES ('425e7701-02c6-4de3-9333-a2459eece1c8', 'mission 2', '2019-02-10', '2019-02-15', 0)

INSERT INTO user (userid, nameuser) VALUES ('0dee5423-6bd9-4014-a690-0993b3cb5f3b', 'user 1')
INSERT INTO user (userid, nameuser) VALUES ('8e70ca41-8766-4188-bf37-3d9a0aae941d', 'user 2')
INSERT INTO user (userid, nameuser) VALUES ('75cb846a-3a7b-4116-8d8a-7778916dff8c', 'user 3')

INSERT INTO missions_users(missionid, userid) VALUES ('de7d9052-4961-4b4f-938a-3cd12cbe1f82', '0dee5423-6bd9-4014-a690-0993b3cb5f3b')
INSERT INTO missions_users(missionid, userid) VALUES ('de7d9052-4961-4b4f-938a-3cd12cbe1f82', '8e70ca41-8766-4188-bf37-3d9a0aae941d')
INSERT INTO missions_users(missionid, userid) VALUES ('425e7701-02c6-4de3-9333-a2459eece1c8', '8e70ca41-8766-4188-bf37-3d9a0aae941d')
INSERT INTO missions_users(missionid, userid) VALUES ('425e7701-02c6-4de3-9333-a2459eece1c8', '75cb846a-3a7b-4116-8d8a-7778916dff8c')

结果

当前，我尝试执行GET个请求，但是将来我将不得不执行POST / PUT / ...个请求。

结果

请求：http://localhost:8082/mission/de7d9052-4961-4b4f-938a-3cd12cbe1f82

{
    "missionid": "de7d9052-4961-4b4f-938a-3cd12cbe1f82",
    "namemission": "mission 1",
    "users": [
        {},
        {}
    ],
    "status": 0,
    "start": "2019-02-10T23:00:00.000+0000",
    "end": "2019-02-12T23:00:00.000+0000"
}

结果除外

请求：http://localhost:8082/mission/de7d9052-4961-4b4f-938a-3cd12cbe1f82

{
    "missionid": "de7d9052-4961-4b4f-938a-3cd12cbe1f82",
    "namemission": "mission 1",
    "users": [
        "user 1",
        "user 2"
    ],
    "status": 0,
    "start": "2019-02-10T23:00:00.000+0000",
    "end": "2019-02-12T23:00:00.000+0000"
}

请求：http://localhost:8082/mission/de7d9052-4961-4b4f-938a-3cd12cbe1f82/users

{
    "user 1",
    "user 2"
}

我不知道如何编写方法来仅获取用户名...

@GetMapping(value = "/{missionId}/users")
public ResponseEntity<?> getUsersByMission(@PathVariable("missionId") String missionId) {
    Mission mission = this.missionResource.findById(missionId).get();
    return new ResponseEntity<>(????, HttpStatus.OK);
}

一种解决方案是使用String列表而不是User列表？

结论

有人可以帮助我取得预期的结果吗？谢谢。

编辑1：@LppEdd答案的结果

[
    {
        "userid": "0dee5423-6bd9-4014-a690-0993b3cb5f3b",
        "nameuser": "user 1",
        "missions": []
    },
    {
        "userid": "8e70ca41-8766-4188-bf37-3d9a0aae941d",
        "nameuser": "user 2",
        "missions": []
    }
]

Answer 1

实际上应该很容易。你快过去了
JPA将为您处理User对象的创建。只需将您的Set<User>暴露给外界即可。

public class Mission {
   ...

   public Set<User> getUsers() {
      return users;
   }

   public void setUsers(final Set<User> users) {
      this.users = users;
   }

   ...
}

然后在@RestController内，保持住并返回Set。

public ResponseEntity<List<String>> getUsersByMission(@PathVariable("missionId") String missionId) {
    final Optional<Mission> mission = this.missionResource.findById(missionId);

    if (mission.isEmpty()) {
       // Handle the "mission not found" case
    }

    final List<String> names = 
                  mission.get().getUsers()
                               .stream()
                               .map(user -> user.getNameUser())
                               .collect(Collectors.toList());

    return ResponseEntity.ok().body(names);
}

要处理双向@ManyToMany关联，您需要指定mappedBy属性，该属性将指向Mission#users字段。

@ManyToMany(mappedBy = "users")
private Set<Mission> missions = new HashSet<>();

使用REST请求获取并更改objets列表的内容

1 个答案: