在spring boot JPA中，如何正确地将实体表示具有外键关联的对象发送到不同的实体？

Question

如果有一个实体包含另一个类的对象，例如book实体中包含publisher实体，该实体如下所示关联：

@ManyToOne
@JoinColumn(name="PUB_CODE", referencedColumnName = "PUB_CODE")
private Publisher pub;

package app.domain;

/*imports*/

@Entity
public class Book implements Serializable{

    /**
     * 
     */
    private static final long serialVersionUID = -6902184723423514234L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

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

    @Column(nullable = false)
    private int pageCount;

    @ManyToOne
    @JoinColumn(name="PUB_CODE", referencedColumnName="PUB_CODE")
    private Publisher pub;


    /*public getters and setters*/

}

publisher.java

package app.domain;

/*imports*/

@Entity
public class Publisher implements Serializable {

    private static final long serialVersionUID = 4750079787174869458L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @Column(name="PUB_CODE",nullable = false, unique = true)
    private String publisherCode;

    @Column(nullable = false)
    private String publisherName;

    /*public getters and setters*/

}

bookrepo.java

package app.service;

/*imports*/

public interface BookRepo extends JpaRepository<Book, Long>{

    @Query("SELECT pb FROM Publisher pb WHERE pb.publisherCode = TRIM(UPPER(:pubCode))")
    public Publisher findPublisherByPubCode(@Param("pubCode")String pubCode);
}

bookcontroller.java

package app.controller;

/*imports*/

@RestController
@RequestMapping(value = "/books")
public class BookController {

    private BookRepo bookRepo;

    @Autowired
    public BookController(BookRepo bookRepo) {
        this.bookRepo = bookRepo;
    }
    //The ApiPathParam is for JSONDOC purposes
    @RequestMapping(value = "/create", method = RequestMethod.POST)
    public List<Book> create(@ApiPathParam(name = "book") @RequestBody Book book, @ApiPathParam(name = "pubCode") @RequestParam("pubCode") String pubCode) {
        // Assume exception handling
        Publisher pbToAttachToThisBook = bookRepo.findPublisherByPubCode(pubCode);
        book.setPub(pbToAttachToThisBook);
        bookRepo.save(book);
        return bookRepo.findAll();
    }
}

{
  "bookName": "goosebumps",
  "id": 0,
  "pageCount": 332,
  "pub": {
    "id": 0,
    "publisherCode": "",
    "publisherName": "",
    "serialVersionUID": 0
  },
  "serialVersionUID": 0
}

Answer 1

您最初发布的技术（传递FK ID，在控制器中手动检索它，并在实体上显式设置它）是有效和安全的。

我不知道有更干净的方法，除非您转到HATEOAS principals，它允许处理资源链接：http://projects.spring.io/spring-HATEOAS/