JPA和Hibernate代理行为 [英] JPA and Hibernate proxy behavior
问题描述
我试图观察下面的JPA2/Hibernate4代理行为，
i tried to observe JPA2 / Hibernate4 proxy behavior below,
//具有延迟加载的循环实体:
// Circular entity with lazy loading:
@Entity
public class Employee {
@Id@Generated
int id;
String name;
@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
Employee boss;
public String toString() {
return id + "|" + name + "|" + boss;
}
//getters and setters ...
}
//坚持存在的实体
// Outer entity:
Employee employee = new Employee();
employee.setName("engineer");
// Inner entity:
Employee boss = new Employee();
boss.setName("manager");
employee.setBoss(boss);
entityTransaction.begin();
entityManager.persist(employee);
entityTransaction.commit();
System.out.println(employee);
//输出:
Hibernate: insert into Employee (id, boss_id, name) values (default, ?, ?)
Hibernate: insert into Employee (id, boss_id, name) values (default, ?, ?)
2|engineer|1|manager|null
//加载外部实体:
String queryString = "select e from Employee e where e.id=" + employee.getId();
Query query = entityManager.createQuery(queryString);
Object loadedEmployee = query.getSingleResult();
System.out.println(loadedEmployee.getClass().getSimpleName());
//输出:
Hibernate: select employee0_.id as id2_, employee0_.boss_id as boss3_2_, employee0_.name as name2_ from Employee employee0_ where employee0_.id=2 limit ?
Employee
令我惊讶的是，上面加载的外部实体仍然是普通实体，但是我希望它是Hibernate proxy由lazy loading产生的结果.我可能在这里错过了一些东西，那么如何正确处理呢?一个简单而具体的示例将不胜感激！
To my surprise the loaded outer entity above is still the plain one, but i'd expected it to be Hibernate proxy resulting from lazy loading. I could have missed something here, so how to get it right? A simple yet concrete example is much appreciated!
@EDIT
根据来自@kostja的回答，我修改了代码并在下面的SE模式下对其进行了调试，因此既无法生成LazyInitializationException，也无法对其进行代理.还有其他提示吗?
According to the answer from @kostja i adapted the code and debugged it in SE mode below, neither could LazyInitializationException be produced, nor was boss property proxied. Any further hints?
@EDIT 2
最后，我将确认@kostja的答案无疑是很棒的.
Finally, i'd confirm that the answer from @kostja is undoubtly great.
我在EE模式下进行了测试，因此在下面观察到了proxied boss property，
I tested in EE mode, so the proxied boss property was observed below,
//LazyInitializationException抛出:
public Employee retrieve(int id) {
Employee employee = entityManager.find(Employee.class, id);
// access to the proxied boss property outside of persistence/transaction ctx
Employee boss = employee.getBoss();
System.out.println(boss instanceof HibernateProxy);
System.out.println(boss.getClass().getSimpleName());
return boss;
}
//放置Spring Tx后绿灯:
@Transactional
public Employee retrieve(int id) ...
//输出:
true
Employee_$$_javassist_0
