EJB 容器中的 ThreadLocal（和 Singleton）

发布于 2024-08-29 00:14:37 字数 731 浏览 5 评论 0原文

我编写了一个授权系统，它依赖于代表当前用户的对象。为了简化编程并提高性能，我想在用户登录后将这些对象保存在 ThreadLocal 中。

它看起来像这样：

public class UserCache {

    private static final ThreadLocal<User> cache = new ThreadLocal<User>();

    public User getCurrentUser() {
        return cache.get();
    }

    public void setCurrentUser(User user) {
        cache.set(user);
    }

}

我读到静态元素会使集群出现问题。如果我在每个集群节点上都有一个 UserCache，那么它们都有自己的缓存对象，不与其他节点上的缓存对象同步。正确的？ UserCache 是单例的典型候选者，因为应用程序只需要它的一个实例。但据我所知，@Singleton EJB 在集群中具有相同的行为。

那么如何使 UserCache 在 EJB 3.1 (Java EE 6) 环境中可集群呢？

从答案中提取的解决方案：

使用 CDI (JSR 299) 中的 SessionScope 或
使用 Terracotta 中的 JVM 集群

原文

I've written an authorization system which relies on objects representing the current user. To simplify programming and increase performance I want to hold those objects in a ThreadLocal after the user has logged in.

It looks like this:

public class UserCache {

    private static final ThreadLocal<User> cache = new ThreadLocal<User>();

    public User getCurrentUser() {
        return cache.get();
    }

    public void setCurrentUser(User user) {
        cache.set(user);
    }

}

I've read that static elements make clustering problematic. If I had an UserCache on each cluster node, they all had their own cache object not synchronized with the cache objects on other nodes. Right? UserCache is a classic candidate for a singleton, because the application needs only a single instance of it. But as far as I know @Singleton EJBs have the same behaviour in a cluster.

So what to do to make UserCache clusterable in an EJB 3.1 (Java EE 6) environment?

Solutions extracted from the answers: