Question

我有两个实体：

@Entity
public class CustomerMainInformation {
@Id @GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;

@Column(unique = true, length = 10)
private String customerNumber;
@OneToMany(mappedBy = "firstCustomerRelationship", cascade = CascadeType.ALL)
private List<CustomerRelationship> firstCustomerRelationship;

@OneToMany(mappedBy = "secondCustomerRelationship", cascade = CascadeType.ALL)
private List<CustomerRelationship> secondCustomerRelationship;
// setter & getter
}

@Entity
public class CustomerRelationship {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@ManyToOne
@JoinColumn(columnDefinition = "first")
private CustomerMainInformation firstCustomerRelationship;

@ManyToOne
@JoinColumn(columnDefinition = "second")
private CustomerMainInformation secondCustomerRelationship;

// setter & getter
}

我执行以下代码：

    CustomerMainInformation customerMainInformation =manager.getReference(CustomerMainInformation.class, 1L);
    System.out.println(customerMainInformation.getFirstCustomerRelationship().size());
    System.out.println(customerMainInformation.getSecondCustomerRelationship().size());

    CustomerMainInformation customerMainInformation2 = manager.getReference(customerMainInformation.getClass(), 2L);
    CustomerRelationship customerRelationship = new CustomerRelationship();
    customerRelationship.setFirstCustomerRelationship(customerMainInformation2);
    customerRelationship.setSecondCustomerRelationship(customerMainInformation);
    manager.persist(customerRelationship);
    transaction.commit();

    EntityManager manager2 = factory.createEntityManager();
    CustomerMainInformation customerMainInformation3 =  manager2.getReference(CustomerMainInformation.class, 1L);
    System.out.println(customerMainInformation3.getFirstCustomerRelationship().size());
    System.out.println(customerMainInformation3.getSecondCustomerRelationship().size());

在此代码关系中，大小增加但是因为.getSecondCustomerRelationship（）在调用之前，列表大小没有改变。

如果@Cacheable（false）添加到CustomerRelationship，.size（）将返回正确的列表大小。

Answer 1

您似乎没有在显示的代码中维护关系的两个方面。调用setSecondCustomerRelationship将设置它的一侧，并且此侧控制db中的外键字段。但是您的java对象模型与您的更改不同步，除非您还将customerRelationship添加到customerMainInformation的集合中。 JPA不会为您维护您的关系，因此如果您改变一方，则您有责任保持另一方不同意。

您可以设置双方，也可以在提交后强制从数据库刷新customerMainInformation。第一种选择效率更高。

eclipselink缓存对象关系

1 个答案: