[解析]Spring Boot：如何在执行post请求时将子项保存在现有父项中

Question

我已经挣扎了几个小时来执行一个POST请求，将一个子（章）保存到父（用户）上。它不能正常工作，我找不到原因....

http://localhost:8080/api/chapters?username=admin
Content-type: application/json
Body: raw

{
    "name": "Product Development", 
}

@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(nullable = false, updatable = false)
private Long id;

@Column(nullable = false, unique = true)
private String username;

@Column(nullable = false)
private String password;

@Column(nullable = false)
private String role;

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "user")
private Set<Chapter> chapters = new HashSet<>();

public void addChapter(Chapter chapter) {
    this.chapters.add(chapter);
    chapter.setUser(this);
}
....
}

@Entity
public class Chapter {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(nullable = false, updatable = false)
private Long id;
    private String name;
@ManyToOne
@JoinColumn(name = "user_id")
private User user;
....

}

@RestController
public class ChapterController {
@Autowired
private ChapterRepository chapterRepository;

@Autowired
private UserRepository userRepository;


@RequestMapping("/chapters")
public Iterable<Chapter> getChapter() {
    return chapterRepository.findAll();
}

@RequestMapping(value="/users/{id}/chapters", method = RequestMethod.GET)
Chapter getChapter(@PathVariable (value = "id") Long id) {
    return chapterRepository.findByUserId(id).get();
}

@PostMapping("/chapters")// issue is here
void newChapter(@RequestParam (value = "username", required=true) 
String username, @RequestBody Chapter newChapter) {
    User user = userRepository.findByUsername(username);
    user.addChapter(newChapter);
    System.out.println(user);
    userRepository.save(user);
    }
}

我希望用父级保存子级，这意味着用user_id=1，因为目前只有一个用户(id=1)。你能告诉我我错过了什么吗？

多谢

--------------更新--------------------------------------------------------------------------------------------------------------------------------------

我不知道为什么，因为在我的应用程序中。属性：

 spring.data.rest.basePath=/api

但不管怎样，这是我的问题...

Answer 1

必须为@manytoone映射添加级联。在用户@entity中更新这一行，它就可以工作了：

@Entity
public class Chapter {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;

    private String name;

    @ManyToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH})
    @JoinColumn(name = "user_id")
    private User user;

}

您可能要做的第二件事是更新控制器，因此它将用户id分配给新的章节，如下所示：

@PostMapping("/chapters")// issue is here
void newChapter(@RequestParam (value = "username", required=true)
                        String username, @RequestBody Chapter newChapter) {
    User user = userRepository.findByUsername(username);
    newChapter.setUser(user);
    user.addChapter(newChapter);
    System.out.println(user);
    userRepository.save(user);
}