标签: orphaned-objects

以一对多关系(国家/地区->)为例.

国家(反面):

@OneToMany(mappedBy = "country", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)
private List<StateTable> stateTableList=new ArrayList<StateTable>(0);

StateTable(拥有方):

@JoinColumn(name = "country_id", referencedColumnName = "country_id")
@ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH, CascadeType.DETACH})
private Country country;

尝试更新StateTable活动数据库事务(JTA或资源本地)中的提供(分离)实体的方法:

public StateTable update(StateTable stateTable) {

    // Getting the original state entity from the database.
    StateTable oldState = entityManager.find(StateTable.class, stateTable.getStateId());
    // Get hold of the original country (with countryId = 67, for example).
    Country oldCountry = oldState.getCountry();
    // Getting …

我想到的场景是:Service Bus用于实例到实例的通信,因此Subscription对每个服务实例都是唯一的.最终结果是,如果实例未正常关闭,则其订阅不会被删除.

当服务实例"死"并重新启动时,订阅的先前内容是不相关的并且可以被丢弃.

那么,有没有办法为Service Bus订阅设置"生存时间"或模拟类似的东西,而不必诉诸一些自定义的孤立检测机制？

重要提示:如果您正在阅读本文,请考虑深入讨论这篇文章.

这是一种很常见的做法/情况/要求,父母的子女可能会迁移到另一方父母.如果orphanRemoval设置true在这种关系的反面,会发生什么？

以一个例子为例,任何简单的一对多关系如下.

反面(部门):

@OneToMany(mappedBy = "department", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)
private List<Employee> employeeList = new ArrayList<Employee>(0);

拥有方(员工):

@JoinColumn(name = "department_id", referencedColumnName = "department_id")
@ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH, CascadeType.DETACH})
private Department department;

合并如下所示的操作/操作(其中department是客户端提供的分离实体),

Employee employee = entityManager.find(Employee.class, 1L);
Department newDepartment = entityManager.contains(department) ? department : entityManager.merge(department);

if (!newDepartment.equals(employee.getDepartment())) {
    employee.getDepartment().getEmployeeList().remove(employee);
    // Since orphanRemoval is set to true, 
    // this should cause a …

我使用以下命令在本地存储库上创建一个孤立分支，然后将其推送到 Github 上的远程：

git checkout --orphan worker
git rm -rf .
git commit --allow-empty -m "Initial orphan commit"
git push origin worker

我在 GitHub 上的工作分支上收到“此分支提前 1 次提交，在 master 后面提交 n 次”消息。