如何在Spring Data Rest中发布和放置两个实体之间的关系@onetomany/@manytoone？

Question

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

@Entity
@Table
public class Author {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)", length = 16)
    private UUID id;

    @Column
    private String name;

    @OneToMany(fetch = FetchType.LAZY, targetEntity = Book.class, mappedBy = "author")
    private List<Book> books;

    // getters and setters

}

@Entity
@Table
public class Book {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)", length = 16)
    private UUID id;

    @Column
    private String title;

    @Column
    private String language;

    @ManyToOne(fetch = FetchType.EAGER, targetEntity = Author.class)
    private Author author;

    // getters and setters

}

@RestResource(path = "authors", rel = "authors")
public interface AuthorRepository extends JpaRepository<Author, UUID> {
}

@RestResource(path = "books", rel = "books")
public interface BookRepository extends JpaRepository<Book, UUID> {
}

{
  "_links" : {
    "authors" : {
      "href" : "http://localhost:8080/authors{?page,size,sort}",
      "templated" : true
    },
    "books" : {
      "href" : "http://localhost:8080/books{?page,size,sort}",
      "templated" : true
    },
    "profile" : {
      "href" : "http://localhost:8080/profile"
    }
  }
}

url http://localhost:8080/authors返回此页面：

{
  "_embedded" : {
    "authors" : [ ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/authors"
    },
    "profile" : {
      "href" : "http://localhost:8080/profile/authors"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 0,
    "totalPages" : 0,
    "number" : 0
  }
}

url http://localhost:8080/books返回此页面：

{
  "_embedded" : {
    "books" : [ ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/books"
    },
    "profile" : {
      "href" : "http://localhost:8080/profile/books"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 0,
    "totalPages" : 0,
    "number" : 0
  }
}

我试图从Book类开始制作一些HTTP POST。

HTTP POST
url: http://localhost:8080/books
header: Content-Type:application/json
payload: { "title": "Book Title" }

Status: 201: Created
Location: http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1

{
  "title" : "Book Title",
  "language" : null,
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1"
    },
    "book" : {
      "href" : "http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1"
    },
    "author" : {
      "href" : "http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1/author"
    }
  }
}

HTTP POST
url: http://localhost:8080/authors
header: Content-Type:application/json
payload: { "name": "Author Name" }

Status: 201: Created
Location: http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11

{
  "name" : "Author Name",
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11"
    },
    "author" : {
      "href" : "http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11"
    },
    "books" : {
      "href" : "http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11/books"
    }
  }
}

HTTP PUT
url: http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11
header: Content-Type:application/json
payload: { "books": ["http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1"] }

Status: 204: No Content
Location: http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11

我有一个响应代码HTTP 204（没有内容）。如果我转到URLhttp://localhost:8080/authors/634D3BD8-ABE6-472B-97CD-04A455BDFB11/Books，我希望得到的结果是这本书，但我得到的结果是：

{
  "_embedded" : {
    "books" : [ ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/authors/634d3bd8-abe6-472b-97cd-04a455bdfb11/books"
    }
  }
}

“Books”属性仍然是空的。为什么？

此外，此URL返回一个空页面:http://localhost:8080/books/61311c9b-b33a-463c-9e6e-8e5efc0a7ad1/author

谢谢

Answer 1

为了使这种情况发生逆转，您的@onetomany(fetch=fetchtype.lazy，targetEntity=book.class,mappedBy=“author”）中应该有cascade选项，以便实际持久化book实体中的更改。

试试这个：

@onetomany(fetch=FetchType.lazy，targetEntity=Book.class，mappedBy=“author”，cascade=CascadeType.all)