如何使用JPA和Hibernate向具有额外列的多对多关联添加数据

huangapple
go评论107阅读模式
英文:

How to add data to Many to Many association with extra column using JPA, Hibernate

问题

以下是翻译好的内容：

我有一个名为 User 的表和一个名为 Book 的表，我想要将它们连接起来。

因此，我创建了第三个名为 Borrow 的表，它具有外键 (book_id, user_id)，以及 takenDate 和 broughtDate 字段。

User.java

  1. @Entity
  2. @Table(name = "Users")
  3. public class User {
  5.     @Id
  6.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  7.     private int id;
  9.     private String name;
  10.     private String surname;
  11.     private String username;
  12.     private String email;
  13.     private String password;
  15.     @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
  16.     private List<Borrow> borrow;
  17.     ....

Book.java

  1. @Entity
  2. @Table(name = "Books")
  3. public class Book {
  5.     @Id
  6.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  7.     private int id;
  9.     private String title;
  10.     private String ISBN;
  11.     private String author;
  12.     private String issuer;
  13.     private Integer dateOfIssue;
  14.     private Boolean IsRented;
  16.     @OneToMany(mappedBy = "book", cascade = CascadeType.ALL, orphanRemoval = true)
  17.     private List<Borrow> borrow;
  18.     .....

Borrow.java

  1. @Entity
  2. @Table(name = "Borrows")
  3. @IdClass(BorrowId.class)
  4. public class Borrow {
  6.     private Date takenDate;
  7.     private Date broughtDate;
  9.     @Id
  10.     @JsonIgnore
  11.     @ManyToOne(fetch = FetchType.LAZY)
  12.     @JoinColumn(name = "book_id", referencedColumnName = "id")
  13.     private Book book;
  15.     @Id
  16.     @JsonIgnore
  17.     @ManyToOne
  18.     @JoinColumn(name = "user_id", referencedColumnName = "id")
  19.     private User user;
  20.     ....

BorrowId.java

  1. public class BorrowId implements Serializable {
  3.     private int book;
  4.     private int user;
  6.     // getters/setters and most importantly equals() and hashCode()
  8.     public int getBook() {
  9.         return book;
  10.     }
  12.     public void setBook(int book) {
  13.         this.book = book;
  14.     }
  16.     public int getUser() {
  17.         return user;
  18.     }
  20.     public void setUser(int user) {
  21.         this.user = user;
  22.     }
  24.     @Override
  25.     public boolean equals(Object o) {
  26.         if (this == o) return true;
  27.         if (!(o instanceof BorrowId)) return false;
  28.         BorrowId borrowId = (BorrowId) o;
  29.         return getBook() == borrowId.getBook() &&
  30.                 getUser() == borrowId.getUser();
  31.     }
  33.     @Override
  34.     public int hashCode() {
  35.         return Objects.hash(getBook(), getUser());
  36.     }
  37. }

我尝试像这样向 Borrow 表中添加数据：

  1. @Transactional
  2. @PostMapping("/addUser/{id}/borrow")
  3. public ResponseEntity<Object> createItem(@PathVariable int id, @RequestBody Borrow borrow, @RequestBody Book book){
  4.     Optional<User> userOptional = userRepository.findById(id);
  5.     Optional<Book> bookOptional = bookRepository.findById(book.getId());
  7.     if(!userOptional.isPresent()){
  8.         throw new UserNotFoundException("id-" + id);
  9.     }
  11.     User user = userOptional.get();
  12.     borrow.setUser(user);
  13.     borrow.setBook(book);
  15.     borrowRepository.save(borrow);
  17.     URI location = ServletUriComponentsBuilder.fromCurrentRequest().path("/{id}").buildAndExpand(borrow.getId()).toUri();
  19.     return ResponseEntity.created(location).build();
  20. }

我还没有完成它，因为我不确定如何操作 :/
欢迎任何提示！

英文:

I have a User table and a Book table that I would like to connect.

So I created third table Borrow that has foreign key (book_id, user_id) and takenDate and broughtDate fields.

User.java

  1. @Entity
  2. @Table(name = &quot;Users&quot;)
  3. public class User {
  6.     @Id
  7.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  8.     private int id;
  10.     private String name;
  11.     private String surname;
  12.     private String username;
  13.     private String email;
  14.     private String password;
  16.     @OneToMany(mappedBy = &quot;user&quot;, cascade = CascadeType.ALL, orphanRemoval = true)
  17.     private List&lt;Borrow&gt; borrow;
  18.     ....

Book.java

  1. @Entity
  2. @Table(name = &quot;Books&quot;)
  3. public class Book {
  5.     @Id
  6.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  7.     private int id;
  9.     private String title;
  10.     private String ISBN;
  11.     private String author;
  12.     private String issuer;
  13.     private Integer dateOfIssue;
  14.     private Boolean IsRented;
  17.     @OneToMany(mappedBy = &quot;book&quot;, cascade = CascadeType.ALL, orphanRemoval = true)
  18.     private List&lt;Borrow&gt; borrow;
  19.     .....

Borrow.java

  1. @Entity
  2. @Table(name = &quot;Borrows&quot;)
  3. @IdClass(BorrowId.class)
  4. public class Borrow {
  6.     private Date takenDate;
  7.     private Date broughtDate;
  9.     //lazy means it will get details of book
  10.     // only if we call GET method
  12.     @Id
  13.     @JsonIgnore
  14.     @ManyToOne(fetch = FetchType.LAZY)
  15.     @JoinColumn(name = &quot;book_id&quot;, referencedColumnName = &quot;id&quot;)
  16.     private Book book;
  19.     @Id
  20.     @JsonIgnore
  21.     @ManyToOne
  22.     @JoinColumn(name = &quot;user_id&quot;, referencedColumnName = &quot;id&quot;)
  23.     private User user;
  24.     ....

BorowId.java

  1. public class BorrowId implements Serializable {
  3.     private int book;
  4.     private int user;
  6.     // getters/setters and most importantly equals() and hashCode()
  8.     public int getBook() {
  9.         return book;
  10.     }
  12.     public void setBook(int book) {
  13.         this.book = book;
  14.     }
  16.     public int getUser() {
  17.         return user;
  18.     }
  20.     public void setUser(int user) {
  21.         this.user = user;
  22.     }
  24.     @Override
  25.     public boolean equals(Object o) {
  26.         if (this == o) return true;
  27.         if (!(o instanceof BorrowId)) return false;
  28.         BorrowId borrowId = (BorrowId) o;
  29.         return getBook() == borrowId.getBook() &amp;&amp;
  30.                 getUser() == borrowId.getUser();
  31.     }
  33.     @Override
  34.     public int hashCode() {
  35.         return Objects.hash(getBook(), getUser());
  36.     }
  37. }

My MySql database design looks like this:

如何使用JPA和Hibernate向具有额外列的多对多关联添加数据

I am trying to add data to Borrow table something like this:

EDITED

  1. @Transactional
  2.     @PostMapping(&quot;/addUser/{id}/borrow&quot;)
  3.     public ResponseEntity&lt;Object&gt; createItem(@PathVariable int id, @RequestBody Borrow borrow, @RequestBody Book book){
  4.         Optional&lt;User&gt; userOptional = userRepository.findById(id);
  5.         Optional&lt;Book&gt; bookOptional = bookRepository.findById(book.getId());
  8.         if(!userOptional.isPresent()){
  9.             throw new UserNotFoundException(&quot;id-&quot; + id);
  10.         }
  12.         User user = userOptional.get();
  13.         borrow.setUser(user);
  14.         borrow.setBook(book);
  16.         borrowRepository.save(borrow);
  18.         URI location = ServletUriComponentsBuilder.fromCurrentRequest().path(&quot;/{id}&quot;).buildAndExpand(borrow.getId()).toUri();
  20.                 return ResponseEntity.created(location).build();
  21.     }

I have't finished it because I am not sure how :/
Any tip is appreciated!

答案1

得分: 0

你已经接近成功了。你只需要记住两件事：

1) 你还需要通过存储库获取Book（目前只获取了User）

2) 所有三个操作必须在同一个事务上下文中进行：

  1. 获取`User`，获取`Book`和保存`Borrow`实体。

提示：你可以将所有这些放在一个Service内，并将其标记为@Transactional，或者将@Post方法标记为@Transactional。我建议第一种选项，但由你决定。

编辑：

  1. Optional<Book> bookOptional = bookRepository.findById(book.getId());

此外，似乎在这里使用@EmbeddedId而不是@IdClass更合适，因为这些id实际上是外键实体：

  1. @Embeddable
  2. public class BorrowId {
  3.    
  4.     @ManyToOne(fetch = FetchType.LAZY)
  5.     @JoinColumn(name = "book_id", referencedColumnName = "id")
  6.     private Book book;
  8.     @ManyToOne
  9.     @JoinColumn(name = "user_id", referencedColumnName = "id")
  10.     private User user;
  11. }

然后在Borrow类中：

  1. @Entity
  2. class Borrow {
  3.   @EmbeddedId 
  4.   BorrowId borrowId;
  5.   ...
  6. }

最后，在Post方法中：

  1. BorrowId borrowId = new BorrowId();
  2. borrowId.setUser(user);
  3. borrowId.setBook(book);
  5. borrow.setBorrowId(borrowId);
  7. borrowRepository.save(borrow);
英文:

You are almost there. You just have to keep in mind two things:

1) You have to fetch the Book via repository as well (you only fetch the User currently)

2) All three operation have to be within the same transactional context:

  1.    fetching of `User`, fetching of `Book` and save `Borrow` entity.

TIP: You can put all these inside a Service and mark it as @Transactional or mark the @Post method as @Transactional. I would suggest first option, but it is up to you.

EDIT:

  1. Optional&lt;Book&gt; bookOptional = bookRepository.findById(book.getId());

Also, it seems adequate to use @EmbeddedId instead of @IdClass here as ids are actual foreign entities:

  1. @Embeddable
  2. public class BorrowId{
  3.    
  4.     @ManyToOne(fetch = FetchType.LAZY)
  5.     @JoinColumn(name = &quot;book_id&quot;, referencedColumnName = &quot;id&quot;)
  6.     private Book book;
  9.     @ManyToOne
  10.     @JoinColumn(name = &quot;user_id&quot;, referencedColumnName = &quot;id&quot;)
  11.     private User user;
  12. }

and then in the Borrow class:

  1. @Entity class Borrow{
  2.   @EmbeddedId BorrwId borrowId;
  3.   ...
  4. }

and in the Post method:

  1.     BorrowId borrowId = new BorrowId();
  2.     borrowId.setUser(user);
  3.     borrowId.setBook(book);
  5.     borrow.setBorrowId(borrowId);
  7.     borrowRepository.save(borrow);

huangapple
  • 本文由 发表于 2020年8月17日 20:49:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/63451175.html
  • hibernate
  • java
  • jpa
  • spring-boot
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定