Question

大家好我刚刚开始学习弹簧靴，并想知道如何通过表单提交保存多对多关系的对象？

说我们有两个图书和出版商实体

@Entity
public class Book{
private long id;
private String name;
private List<Publisher> publishers;

public Book() {

}

public Book(String name) {
    this.name = name;
}

public Book(String name, Set<Publisher> publishers){
    this.name = name;
    this.publishers = publishers;
}

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getName() {
    return name;
}

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

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "book_publisher", joinColumns = @JoinColumn(name = "book_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "publisher_id", referencedColumnName = "id"))
public List<Publisher> getPublishers() {
    return publishers;
}

public void setPublishers(List<Publisher> publishers) {
    this.publishers = publishers;
  }
}

@Entity
public class Publisher {
private Long id;
private String name;
private List<Book> books;

public Publisher(){

}

public Publisher(String name){
    this.name = name;
}

public Publisher(String name, List<Book> books){
    this.name = name;
    this.books = books;
}

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getName() {
    return name;
}

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

@ManyToMany(mappedBy = "publishers")
public List<Book> getBooks() {
    return books;
}

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

然后我们有一个图书库

public interface BookRepository extends CRUDRepository<Book, Long>{
}

如何在bookcontroller中使用crud方法？

Answer 1

真正的问题是“连接表”有附加数据，例如发布者出版书籍的日期，该出版商的书籍ISBN等等...... 如果答案是肯定的，那么它需要另一个表格，这解决了您的问题，如果没有，您从您输入的图书的出版商的表单列表中收到，并将它们分别添加到连接表和书籍到书表通过书库... 从我的角度来看，数据库的设计缺乏信息。当你回答这个问题的时候，我会试着帮你做春天的事...... 当前从db的角度来看，在需要现有对象的对象之间进行这种连接。而fromwise的第一个阶段是Publisher的形式和Book的形式。众所周知，许多人都很头疼。我建议在问题中添加JPA标记，然后删除spring-data。

Spring boot + jpa，通过表单提交进行多对多关联

1 个答案: