java - 在带有 Spring REST JPA 的自定义 REST Controller 中使用链接资源

Question

我正在数据库上开发一组 REST 资源，并使用 Spring Data Rest 公开核心 CRUD 功能，以直接与存储库交互。

在我的简化示例中，我有用户:

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long id;

    public String name;

    @OneToMany(mappedBy = "user")
    public Collection<Project> projects;
}

和用户自己的项目:

@Entity
public class Project {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long id;

    public String name;

    public String oneOfManyComplexDerivedProperties;

    @ManyToOne
    public User user;
}

直接与存储库交互是可以的，因此对于创建用户(其他简单实体)，问题在于创建项目。项目有大量基于用户表单输入的服务器派生字段，因此我编写了一个自定义 Controller 来生成它们并保留结果。 为了保留结果，我需要将项目与其所属的用户关联起来。我希望我的客户能够为此使用用户链接，就像通过直接访问存储库创建新实体时一样(直接访问存储库就可以了):

@RepositoryRestController
public class CustomProjectController {

    @Autowired
    ProjectRepo projectRepo;

    @RequestMapping(value = "/createProject", method = RequestMethod.POST)
    public HttpEntity<Project> createProject(@RequestParam User userResource,
                                         @RequestParam String formField1, // actually an uploaded file that gets processed, but i want simple for example purposes
                                         @RequestParam String formfield2)
{
    Project project = new Project();

    /*
    Actually a large amount of complex business logic to derive properties from users form fields, some of these results are binary.
     */
    String result = "result";
    project.oneOfManyComplexDerivedProperties = result;
    project.user = userResource;
    projectRepo.save(project);

    // aware that this is more complex than I've written.
    return ResponseEntity.ok(project);
}
}

当我打电话时:
<a href="http://localhost:9999/api/createProject?userResource=http://localhost:9999/api/users/1&formField1=data1&formField2=Otherdata" rel="noreferrer noopener nofollow">http://localhost:9999/api/createProject?userResource=http://localhost:9999/api/users/1&formField1=data1&formField2=Otherdata</a>

我得到:

{
    "timestamp": 1510588643801,
    "status": 400,
    "error": "Bad Request",
    "exception": "org.springframework.web.method.annotation.MethodArgumentTypeMismatchException",
    "message": "Failed to convert value of type 'java.lang.String' to required type 'com.badger.User'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'http://localhost:9999/api/users/1'; nested exception is java.lang.NumberFormatException: For input string: \"http://localhost:9999/api/users/1\"",
    "path": "/api/createProject"
}

如果我将 userResource 更改为类型 Resource然后我得到一个不同的错误:
"Failed to convert value of type 'java.lang.String' to required type 'org.springframework.hateoas.Resource'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.hateoas.Resource': no matching editors or conversion strategy found"

我在文档中找不到任何关于在自定义 Controller 中使用存储库 URI 的引用，我找到的最接近的是 Resolving entity URI in custom controller (Spring HATEOAS)但自编写以来 API 已经发生了变化，我无法让它工作。

Answer 1

我建议你真正应该做的是:

http://localhost:9999/api/users/1/projects?formField1=data1&formField2=Otherdata

通过启用 Spring Data 的 Web 支持，您可以将路径变量自动绑定(bind)到实体实例。

@RequestMapping(value = "users/{id}/projects", method = RequestMethod.POST)
        public HttpEntity<Project> createProject(
                            @PathVariable("id") User user,
                            @RequestParam String formField1,
                            @RequestParam String formfield2)
{

}

https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#core.web