Java @OneTONE映射不保存MySQL。JpaRepository

我有一对一关系中的两个模型，但当我试图保存它时，会提供一个ID错误

@Entity
@Table(name = "app_a_table")
class A {
    
    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    ...

    @OneToOne(mappedBy = "a", cascade = CascadeType.ALL)
    private B b;

    ...
    // Constructor
    // Getter & Setter
}

@Entity
@Table(name = "app_b_table")
class B {
    
    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    ...

    @OneToOne()
    @JoinColumn(name = "A_ID", referencedColumnName = "ID")
    private A a;

    ...
    // Constructor
    // Getter & Setter
}

当我试图像下面这样储蓄时

A newA = new A()
B newB = New B()

newB.setProperties().....

newA.setB(newB);

aRepository.save(newA);

引发的异常列“A_ID”不能为null

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如何避免冲突

您的映射是双向的，因此您还必须以这种方式进行维护：

A newA = new A()
B newB = New B()

newB.setProperties().....

newA.setB(newB);
// add this:
newB.setA(newA);

aRepository.save(newA);

---

首先保持

newB

或确保

cascade

处于打开状态请提供异常的堆栈跟踪