JpaRepository删除子元素 [英] JpaRepository delete child elements

问题描述

我试图做一个非常简单的删除操作，但不知何故，它不起作用，因为我更新了DAO到JpaRepository。基本上是这样的：

  A a = aRepository.findOne（id）; 
 a.setSomeField（someNewString）; 
 
列表< B> bList = a.getBs（）; 
 bList.clear（）; 
repository.saveAndFlush（a）; 
  

字段get按预期更新，但 bList 保持不变。我甚至试过：

  A a = aRepository.findOne（id）; 
 a.setSomeField（someNewString）; 
 
列表< B> bList = a.getBs（）; （b b：bList）{
 bRepository.delete（b）; 
 
} 
 bRepository.flush（）; 
 bList.clear（）; 
repository.saveAndFlush（a）; 
  

还是一样...

A类看起来像这样：

  @Entity 
 @Table（name =A）
 public类A实现Serializable {
 private static final long serialVersionUID = -1286451120913657028L; 
 
 @Column（name =id，length = 16，nullable = false，updatable = false）
 @GenericGenerator（name =uuid，strategy =uuid2）
 @GeneratedValue（generator =uuid）
 @Basic（fetch = FetchType.EAGER）
 @Id 
受保护的UUID ID; 
 
 @OneToMany（mappedBy =a，fetch = FetchType.EAGER）
 @Cascade（{CascadeType.ALL}）
 List< B> bList; 
 
 // getter + setter 
} 
  

我是什么做错了！

---

B类：

  @Entity 
 @Table（name =B）
 public class B implements Serializable {
 @Column（name =id，length = 16，nullable = false，updatable = false）
 @GenericGenerator（name =uuid，strategy =uuid2）
 @GeneratedValue（generator =uuid）
 @Basic（fetch = FetchType。 EAGER）
 @Id 
受保护的UUID ID; 
 
 @ManyToOne（可选= false）
 @JoinColumns（{@JoinColumn（name =A_id，referencedColumnName =id，nullable = false）}）
 @Valid 
 A a; 
 
 // setter + getter 
} 
  

Setters and getters无论如何都是如此简单：

  public List< B> getBList（）{
 return bList; 
} 
 
 public void setBList（List< B> bList）{
 this.bList = bList; 
 
 
 
 
 
 $ b 
更多信息： 
 $ / p> 
 
 
 
 
 spring 3.2.2 
 
 
 hibernate 4.2.2 
 
 
 spring-data-commons 1.5.1 
 
 
 spring-data-jpa 1.3.2 
 
 
 
 
解决方案
更新 A.bList 属性如下： 
 
 
  public class A {
 @OneToMany（mappedBy =a，fetch = FetchType.EAGER，cascade = CascadeType.ALL，orphanRemoval = true）
 List< B> bList; 
 
  
  orphanRemoval = true  annotation属性将告诉基础JPA实现删除没有任何父级的B记录。
 
 
 
另外，由于 B  side管理关联，您应该在中断关系时清除它的 a 属性。为了更容易阅读并从调用者中移除这些实现细节的负担，您应该在 A 中引入管理方法： 
 
 
  public class A {
 public void clearBList（）{
 for（B b：bList）{
 b.releaseA（）; 
} 
 bList.clear（）; 
 
 
 
 public class B {
 void releaseA（）{
 this.a = null; 
 
 
 
 
 $ b 
你应该避免直接暴露集合，而是返回一个不可变的它的版本，以防止客户在没有A类知道的情况下直接修改集合。  A 管理 B 列表，所以它应该完全控制它！
  public class A {
 public List< B> getBList（）{
返回Collections.unmodifiableList（bList）; 
} 
} 
  
希望有帮助。
 
I'm trying to do a very simple delete operation, but somehow it doesn't work since I updated the DAOs to JpaRepository. Basically it's this:
A a = aRepository.findOne(id);
a.setSomeField("someNewString");

List<B> bList = a.getBs();
bList.clear();
aRepository.saveAndFlush(a);
The field get's updated as expected, but the bList stays unchanged. I've even tried:
A a = aRepository.findOne(id);
a.setSomeField("someNewString");

List<B> bList = a.getBs();
for(B b : bList) {
   bRepository.delete(b);
}
bRepository.flush();
bList.clear();
aRepository.saveAndFlush(a);
Still the same...

Class A looks like this:
@Entity
@Table(name = "A")
public class A implements Serializable {
    private static final long serialVersionUID = -1286451120913657028L;

    @Column(name = "id", length = 16, nullable = false, updatable = false)
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @GeneratedValue(generator = "uuid")
    @Basic(fetch = FetchType.EAGER)
    @Id
    protected UUID id;

    @OneToMany(mappedBy = "a", fetch = FetchType.EAGER)
    @Cascade({ CascadeType.ALL })
    List<B> bList;

    // getter + setter
}
What am I doing wrong?!



Class B:
@Entity
@Table(name = "B")
public class B implements Serializable {
    @Column(name = "id", length = 16, nullable = false, updatable = false)
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @GeneratedValue(generator = "uuid")
    @Basic(fetch = FetchType.EAGER)
    @Id
    protected UUID id;

    @ManyToOne(optional = false)
    @JoinColumns({ @JoinColumn(name = "A_id", referencedColumnName = "id", nullable = false) })
    @Valid
    A a;

    // setter + getter
}
Setters and getters are all just as simple as possbile:
public List<B> getBList() {
    return bList;
}

public void setBList(List<B> bList) {
    this.bList = bList;
}




Some more information:


spring 3.2.2
hibernate 4.2.2
spring-data-commons 1.5.1
spring-data-jpa 1.3.2

解决方案
Update the A.bList property as follows:
public class A {
    @OneToMany(mappedBy = "a", fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true)
    List<B> bList;
}
The orphanRemoval = true annotation attribute will tell the underlying JPA implementation to delete B records which don't have any parent left.

Also, Since the B side manages the association, you should clear its a attribute when breaking the relationship. To make this easier to read and to remove the burden of such implementation details from the caller, you should introduce management methods in A :
public class A {
    public void clearBList() {
        for (B b : bList) {
            b.releaseA();
        }
        bList.clear();
    }
}

public class B {
    void releaseA() {
        this.a = null;
    }
}
You should avoid exposing collections directly and instead return an immutable version of it to prevent clients to the A class of modifying the collection directly without the A class knowing it. A manages the B list, so it should have full control over it!
public class A {
    public List<B> getBList() {
        return Collections.unmodifiableList(bList);
    }
}
Hope that helps.

                        
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