spring-boot-starter-data-jpa @OneToMany 在更新时不会插入新子项

Question

家长：

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entity
public class A {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
public Long id;

@OneToMany(cascade = {CascadeType.ALL}, orphanRemoval = true)
public List<Child> child = new LinkedList<>();

}

孩子：

@Entity
public class Child {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
public Long child_id;

}

存储库：

import org.springframework.data.repository.CrudRepository;
@Transactional
public interface ARepository extends CrudRepository<A,Long> {

@Query("SELECT x FROM A x WHERE x.syncTimestamp IS NULL")
List<A> findAs();
}

坚持：更新

public class SomeClass {

  @Autowired
  private ARepository repo;

  public void someMethod() {

    List<A> as = repo.findAs();
    A firstA = as.get(0);
    firstA.child.add(new Child());
    repo.save(firstA);
  }    

}

当我插入一个新的 A 对象时，一切正常，所有子项都很好地插入到数据库中。

但是当我从数据库加载一个 A 对象时，将一些子项添加到列表中然后更新该对象，这不会插入新的子项。

根据 CascadeType 的文档，所有人都应该插入它们。

知道如何解决这个问题吗？

Answer 1

那是因为您没有对Child类中的A类的引用：

@Entity
public class A {
...
     @OneToMany(mappedBy = "a", cascade = {CascadeType.ALL}, orphanRemoval = true)
     public List<Child> child = new LinkedList<>();
}

@Entity
public class Child {
...
    @ManyToOne
    @JoinColumn(name = "your_table_name")
    private A a;
...
}

Answer 2

这个对我有用。 请按照以下方式重试您的子实体将得到更新：

public class SomeClass {

    @Autowired
    private ARepository repo;

    public void someMethod() {

        List<A> as = repo.findAs();
        A firstA = as.get(0);
        List<Child> childs=firstA.getChild();

        // add new child value
        childs.add(new Child("Test"));
        firstA.setChild(childs);

        for (Child child : childs) {
            child.setA(firstA);
        }
        repo.save(firstA);
    }    

}


import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinTable;
import javax.persistence.ManyToOne;

@Entity
public class Child {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    public Long child_id;

    public Child(String name) {
        // TODO Auto-generated constructor stub
        this.name=name;
    }

    public Child() {
        // TODO Auto-generated constructor stub
    }
    private String name;

    @ManyToOne
    @JoinColumn(name="a_id")
    private A a;

    //your getter setter

}

import java.util.LinkedList;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entity
public class A {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    public Long id;

    private String syncTimestamp=null;

    @OneToMany(mappedBy="a", cascade=CascadeType.ALL)
    public List<Child> child = new LinkedList<>();

    // your getter setter

}