使用父引用成功添加子实体后，子资源不显示在父资源下 [英] After successfully adding child entity with parent reference, child does not show under parent resource

问题描述

我有两个实体，Shelf 和 Book.一个 Shelf 可以有多个 Books(这种关系是双向的).我已经将这两个公开为 JpaRepositories.

I have two entities, Shelf and Book. A Shelf can have multiple Books (the relationship is bi-directional). I've exposed both of these as JpaRepositories.

问题来了:

1. 我通过将 { "name":"sci-fi" } 发布到/shelves.(success) 来创建一个书架
2. 我通过将 { "name":"mybook", "shelf":"localhost:8080/shelves/1" } 发布到/books 来为该书架创建一本书.(成功)
3. 当我拿到我刚在/books/1 创建的书时，它有指向父书架的正确链接.
4. 但是当我去书架/1/books 时，我得到一个空结果，{ }！

有什么我可能遗漏的想法吗?

Any ideas what I might be missing?

现在我已经通过在 beforeCreate 事件中显式地将这本书添加到书架上构建了一个解决方法，但这似乎完全没有必要.(不过，它确实解决了问题.)

Right now I've constructed a workaround by explicitly adding the book to its shelf in a beforeCreate event, but it seems like this should be totally unnecessary. (It does fix the problem, however.)

@HandleBeforeCreate(Book.class)
public void handleCreate(Book book) {
  // why is this necessary?
  book.getShelf().getBooks().add(book); 
}

以下是实体类:

@Entity
public class Book {

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

    private String name;

    @ManyToOne
    private Shelf shelf;

    public Shelf getShelf() {
    return shelf;
    }

    public void setShelf(Shelf shelf) {
    this.shelf = shelf;
    }

    public String getName() {
    return name;
    }

    public void setName(String name) {
    this.name = name;
    }

    @Override
    public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
    }

    @Override
    public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Book other = (Book) obj;
    if (name == null) {
        if (other.name != null)
        return false;
    } else if (!name.equals(other.name))
        return false;
    return true;
    }
}

@Entity
public class Shelf {

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

    private String name;

    @OneToMany
    private List<Book> books = new ArrayList<Book>();

    public List<Book> getBooks() {
    return books;
    }

    public void setBooks(List<Book> books) {
    this.books = books;
    }

    public String getName() {
    return name;
    }

    public void setName(String name) {
    this.name = name;
    }

    @Override
    public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
    }

    @Override
    public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Shelf other = (Shelf) obj;
    if (name == null) {
        if (other.name != null)
        return false;
    } else if (!name.equals(other.name))
        return false;
    return true;
    }

}

我使用的是 Spring Boot 1.1.8.

I'm using Spring Boot 1.1.8.

推荐答案

在你的 Shelf 实体中，将 mappedBy = "self" 属性添加到 @OneToMany 注释中书籍:

In your Shelf entity, add the mappedBy = "self" property to the @OneToMany annotation in books:

@OneToMany(mappedBy = "self")
private List<Book> books = new ArrayList<Book>();

这将使用与 self 的引用匹配的书籍自动填充书籍列表.

This will auto populate the list of books with the books whose reference to self matches.

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