Question

我正在尝试将Set放在另一个Object中。例如：

我正在返回一个论坛列表，但在那些论坛中它包含一些线程。我在调用函数时如何获取这些线程：

@GET
@Produces({MediaType.APPLICATION_JSON})
public Response findAll() {
    List<Forum> forums = new ArrayList<>();

    Forum forum = new Forum();
    WebAccount account = new WebAccount("", "", "", Gender.MALE, Long.MAX_VALUE);
    forum.setAccount(account);

    List<ForumThread> threads = new ArrayList<>();

    ForumThread thread = new ForumThread();
    thread.setAccount(account);
    thread.setId(1);
    thread.setName("sweg");
    thread.setDescription("LOLOL");

    forum.setThreads(threads);
    forum.setId(1);

    Forum forum1 = new Forum();
    WebAccount account1 = new WebAccount("", "", "", Gender.MALE, Long.MAX_VALUE);
    forum1.setAccount(account1);
    forum1.setId(2);

    forums.add(forum);
    forums.add(forum1);
    GenericEntity<List<Forum>> entity = new GenericEntity<List<Forum>>(forums) {};
    return Response.ok(entity).build();
}

我想知道两件事：

获取所有主题但仅包含ID号。
获取每个线程的完整线程信息。

论坛课程：

@Entity
@NamedQueries({})
@XmlRootElement
@Table(name="Website_Forum")
public class Forum implements Serializable {

@Id
@Column(unique = true, nullable = false, length = 16)
@TableGenerator(name = "ForumSEQ", allocationSize = 1, initialValue = 1)
@GeneratedValue(strategy = GenerationType.TABLE, generator = "ForumSEQ")
private Integer id;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "webaccount_id")
private WebAccount account;

@Column(unique = true, nullable = false, length = 64)
private String name;

@Column(unique = false, nullable = false, length = 1024)
private String description;

@OneToMany(cascade = CascadeType.ALL)
@LazyCollection(LazyCollectionOption.FALSE)
@JoinTable(name = "Website_ForumThreads", 
        joinColumns = @JoinColumn(name = "forum_id", referencedColumnName = "id"), 
        inverseJoinColumns = @JoinColumn(name = "thread_id", referencedColumnName = "id"))
private List<ForumThread> threads;

public Forum() {
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public WebAccount getAccount() {
    return account;
}

public void setAccount(WebAccount account) {
    this.account = account;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public List<ForumThread> getThreads() {
    return threads;
}

public void setThreads(List<ForumThread> threads) {
    this.threads = threads;
}
}

有人可以解释我为什么没有得到任何线程吗？当我调用函数时，这是我的JSON输出：

[
  {
    "account": {
      "dateOfBirth": 9223372036854775807,
      "email": "",
      "gender": "MALE",
      "helpId": "9c5ee012-4c35-4c6c-be0f-aa8b383642a5",
      "helpType": "ACCOUNT_CREATE",
      "information": "A new account!",
      "isBanned": false,
      "password": "",
      "permissionGroup": "REGULAR",
      "profilePicture": "/Media/ProfilePictures/default.png",
      "username": ""
    },
    "id": 1,
    "threads": []
  },
  {
    "account": {
      "dateOfBirth": 9223372036854775807,
      "email": "",
      "gender": "MALE",
      "helpId": "590b8ccb-5c96-4044-8e58-424f5d5287c6",
      "helpType": "ACCOUNT_CREATE",
      "information": "A new account!",
      "isBanned": false,
      "password": "",
      "permissionGroup": "REGULAR",
      "profilePicture": "/Media/ProfilePictures/default.png",
      "username": ""
    },
    "id": 2
  }
]

Answer 1

有人可以解释我为什么没有得到任何线程吗？

在您的实际代码中：

List<ForumThread> threads = new ArrayList<>();

ForumThread thread = new ForumThread();
thread.setAccount(account);
thread.setId(1);
thread.setName("sweg");
thread.setDescription("LOLOL");

forum.setThreads(threads);
forum.setId(1);

您没有在threads列表中添加任何内容，只是创建Thread对象而不将其添加到列表中，然后返回空List。

在将创建的Thread对象设置为Forum对象之前，应将其添加到列表中。

threads.add(thread); //add the created thred to your List
forum.setThreads(threads);
forum.setId(1);

修改

回答你的第二个问题：

获取所有主题但仅包含ID号。

要仅获得ID中Threads的{{1}}，您应该创建一个具有List属性的自定义DTO对象，并且{ {1}}只保留Forum类的List<Integer>个，并使用自定义代码填充此列表。

Hibernate~RESTful返回一个对象集

1 个答案: