@RepositoryRestResource中m对n关系的处理

Question

public void setUsers(Set<AppUser> users) {
    users.forEach(u -> u.getGroups().add(this));
    this.users = users;
}

这样我就可以

POST http://localhost:8080/groups

{
  "name": "Group X",
  "users": ["http://localhost:8080/users/1"]
}

但我的问题是，这对我来说并不合适--它看起来确实像是一种变通方法，而不是真正的Spring方式来实现这个需求。所以..

我目前正在努力使用Spring的@repositoryrestresource创建关系资源。我想创建一个新组，并将其与调用用户关联，如下所示：

POST http://localhost:8080/users/1/groups

{
  "name": "Group X"
}

但是唯一的结果是响应204没有内容。我不知道为什么。这可能与我的另一个问题有关，也可能与我的另一个问题无关（请参见此处），我试图通过在JSON有效负载中设置相关资源来实现同样的问题--但这也不起作用。

服务器端我得到以下错误：

tion$ResourceSupportHttpMessageConverter : Failed to evaluate Jackson deserialization for type [[simple type, class org.springframework.hateoas.Resources<java.lang.Object>]]: java.lang.NullPointerException

请让我知道，如果你需要任何具体的代码。

@RepositoryRestResource(collectionResourceRel = "groups", path = "groups", exported = false)
public interface UserGroupRepository extends JpaRepository<UserGroup, Long> {
    List<UserGroup> findByName(@Param("name") String name);
}

PATCH http://localhost:8080/users/1

{
  "groups": [
    {
      "name": "Group X"
    }
  ]
}

@Autowired
private TestRestTemplate template;

private static String USERS_ENDPOINT = "http://localhost:8080/users/";
private static String GROUPS_ENDPOINT = "http://localhost:8080/groups/";

// ..

@Test
@DirtiesContext(classMode = ClassMode.BEFORE_EACH_TEST_METHOD)
public void whenCreateUserGroup() {

    // Creates a user
    whenCreateAppUser();

    ResponseEntity<AppUser> appUserResponse = template.getForEntity(USERS_ENDPOINT + "1/", AppUser.class);
    AppUser appUser = appUserResponse.getBody();

    UserGroup userGroup = new UserGroup();
    userGroup.setName("Test Group");
    userGroup.setUsers(Collections.singleton(appUser));

    template.postForEntity(GROUPS_ENDPOINT, userGroup, UserGroup.class);

    ResponseEntity<UserGroup> userGroupResponse = template.getForEntity(GROUPS_ENDPOINT + "2/", UserGroup.class);

    Predicate<String> username = other -> appUser.getUsername().equals(other);

    assertNotNull("Response must not be null.", userGroupResponse.getBody());

    assertTrue("User was not associated with the group he created.",
            userGroupResponse.getBody().getUsers().stream()
                    .map(AppUser::getUsername).anyMatch(username));
}

userGroup.setUsers(Collections.singleton(appUser)); 

将中断此测试并返回404错误请求。

Answer 1

根据SDR参考：

邮政

仅支持集合关联。向集合中添加新元素。支持的媒体类型：

POST http://localhost:8080/users/1/groups (with Content-Type:text/uri-list)
http://localhost:8080/groups/1