根实体及其集合的不同缓存并发策略（Hibernate 与 EHCache）？

Question

给出的示例来自 Hibernate docs 并修改它，以便根级实体（客户）是只读的，而其集合之一（票证）是读写的：

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
public class Customer { 
    ... 
    @OneToMany(...)
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    public SortedSet<Ticket> getTickets() {
        return tickets;
    }
    ...
}

从缓存访问客户时，票证集合会刷新吗？

Answer 1

如果您在其他地方修改给定客户的一张票据，是的。你为什么不测试一下这个？我们假设 Cutomer#1 在其 tickets 集合中具有 Ticket#1 和 Ticket#2。我运行了这段代码：

// loading in first session
Session session1 = HibernateUtil.getSession();
Transaction tx1 = session1.beginTransaction();
Customer c1 = (Customer) session1.load(Customer.class, 1L); // loads from db and puts in cache
for (Ticket ticket : c1.getTickets()) { // caches q2742145.Customer.tickets#1
    System.out.println(ticket);
}
Ticket ticket = (Ticket) session1.load(Ticket.class, 1L); // doesn't hit the db
ticket.setName("foo"); // do some change on Ticket#1
session1.save(ticket);
tx1.commit(); // Ticket#1 gets updated in the db and the cached association invalidated

// loading in second session
Session session2 = HibernateUtil.getSession();
Transaction tx2 = session2.beginTransaction();
Customer c2 = (Customer) session2.load(Customer.class, 1L); // hits the cache
Set<Ticket> tickets = c2.getTickets();
for (Ticket ticket2 : tickets) { // reloads tickets from db
    System.out.println(ticket2); 
}
tx2.commit();

这表明票证集合被“刷新”。