Wildfly 10.1.0 Final Remoting 端点任务线程不断增长答案

【问题标题】：Wildfly 10.1.0 Final Remoting endpoint task threads keep growingWildfly 10.1.0 Final Remoting 端点任务线程不断增长
【发布时间】：2019-02-04 21:49:16
【问题描述】：

我们正在使用 Wildfly 10.1.0 Final。

我们遇到了由于线程不断增长导致的 OutOfMemoryError。

检查线程转储后。

我们发现有数千个远程“端点”任务-N线程。

远程处理“端点”任务-N 个线程有什么用？

它们是由 jobss-remoting 创建的吗？

重启服务器后，我们发现一开始只有16个线程：

远程处理“端点”任务 1 ~ 远程处理“端点”任务 16。

服务器运行几天或几个月后，可能会有成百上千个远程处理线程：

下面列出了一个线程转储的 sn-p。

在这个线程转储中，有几个不同编号的“Remoting "endpoint" task-11”。

其他任务也是如此，例如任务 1 到任务 16。

所有这些线程都在等待。

"Remoting "endpoint" task-11" #55415 daemon prio=5 os_prio=0 tid=0x00007f2b8c0a8000 nid=0x276e waiting on condition [0x00007f280a36c000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabee2b8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-11" #55417 daemon prio=5 os_prio=0 tid=0x00007f2ba003f800 nid=0x276d waiting on condition [0x00007f2794818000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabecf40> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-11" #55414 daemon prio=5 os_prio=0 tid=0x00007f2b98023800 nid=0x276b waiting on condition [0x00007f2792bfc000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabeda50> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-10" #55411 daemon prio=5 os_prio=0 tid=0x00007f2ba003e000 nid=0x276a waiting on condition [0x00007f27926f7000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabecf40> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-10" #55413 daemon prio=5 os_prio=0 tid=0x00007f2b8c0a7000 nid=0x2769 waiting on condition [0x00007f27927f8000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabee2b8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-10" #55412 daemon prio=5 os_prio=0 tid=0x00007f2b98022800 nid=0x2768 waiting on condition [0x00007f27c4815000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabeda50> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-9" #55372 daemon prio=5 os_prio=0 tid=0x00007f2c7408f000 nid=0x41df waiting on condition [0x00007f27907d8000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-8" #55369 daemon prio=5 os_prio=0 tid=0x00007f2c7408d000 nid=0x41dd waiting on condition [0x00007f27909da000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-7" #55368 daemon prio=5 os_prio=0 tid=0x00007f2c7408b000 nid=0x41dc waiting on condition [0x00007f2790adb000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-6" #55367 daemon prio=5 os_prio=0 tid=0x00007f2c74089000 nid=0x41db waiting on condition [0x00007f2790bdc000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-5" #55366 daemon prio=5 os_prio=0 tid=0x00007f2c74087000 nid=0x41da waiting on condition [0x00007f2790cdd000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-4" #55365 daemon prio=5 os_prio=0 tid=0x00007f2c74085000 nid=0x41d9 waiting on condition [0x00007f2790dde000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabece88> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-9" #55364 daemon prio=5 os_prio=0 tid=0x00007f2bd813c000 nid=0x41d8 waiting on condition [0x00007f2790edf000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabed500> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


"Remoting "endpoint" task-9" #55363 daemon prio=5 os_prio=0 tid=0x00007f2bf4044000 nid=0x41d7 waiting on condition [0x00007f2790fe0000]
   java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x00000006eabee3c0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

....

20180903

我发现“远程处理“端点”任务”线程是由“xnio”创建的。而且我发现有一个 xnio 的 issue 和我们的场景非常相似：

https://issues.jboss.org/browse/XNIO-285

它说这个问题已在“xnio 3.6.0.Beta1”中修复。不幸的是，Wildfly 10.1.0 使用的是 xnio 3.4.0。当我尝试升级到 xnio 3.6.5 时，我得到了 org/wildfly/common/context/Contextual 的 java.lang.NoClassDefFoundError。升级包含“org/wildfly/common/context/Contextual”类的wildfly-common-1.4.0.Final.jar后，NoClassDefFoundError仍然存在。

还有其他方法可以防止远程“端点”任务线程增长吗？

【问题讨论】：

您是否使用作用域 EJB 上下文来执行远程方法？

标签： java jboss wildfly-10

【解决方案1】：

您可能正在使用scoped EJB 上下文进行远程方法执行。

每个作用域的 EJB 上下文都会创建新线程，并且简单地调用 context.close() 方法不会关闭上下文，因此您会得到 OutOfMemoryError

如何关闭作用域 EJB 客户端上下文？

答案是一样的，在 EJB 客户端上下文中使用 close() 方法。但真正的问题是如何获得与 JNDI 上下文相关联的相关作用域 EJB 客户端上下文。在我们开始之前，了解用于 EJB 查找的 ejb:JNDI 名称空间以及 JNDI 上下文（通常是您在客户端代码中看到的 InitialContext）之间的关系非常重要。 Java 语言提供的 JNDI API 允许在 JNDI 框架中注册“URL 上下文工厂”（详见 http://docs.oracle.com/javase/jndi/tutorial/provider/url/factory.html）。如该文档所述，URL 上下文工厂可用于在 JNDI 查找期间解析 URL 字符串。这就是执行远程 EJB 查找时的 ejb: 前缀。 ejb: URL 字符串由 URL 上下文工厂支持。

在内部，当查找 ejb: URL 字符串时，会为该 ejb: 查找创建相关的 javax.naming.Context。让我们看一些代码以便更好地理解：

// JNDI context "A"
Context jndiCtx = new InitialContext(props);
// Now let's lookup a EJB
MyBean bean = jndiCtx.lookup("ejb:app/module/distinct/bean!interface");

所以我们首先创建一个 JNDI 上下文，然后使用它来查找 EJB。使用 ejb: JNDI 名称的 bean 查找虽然只是一种说法，但它还涉及到更多的东西。当您查找该字符串时，实际发生的情况是为 ejb: URL 字符串创建了一个单独的 javax.naming.Context。然后使用这个新的 javax.naming.Context 来查找该 JNDI 名称中的其余字符串。

让我们将这一行分解为多个语句以便更好地理解：

// Remember, the ejb: is backed by a URL context factory which returns a Context for the ejb: URL (that's why it's called a context factory)
final Context ejbNamingContext = (Context) jndiCtx.lookup("ejb:");
// Use the returned EJB naming context to lookup the rest of the JNDI string for EJB
final MyBean bean = ejbNamingContext.lookup("app/module/distinct/bean!interface");

正如您在上面看到的，我们将单个语句拆分为几个语句，以便更好地解释细节。如您所见，当 ejb: URL 字符串被解析为 JNDI 名称时，它获取了 javax.naming.Context 实例。此实例不同于用于进行查找的实例（本例中为 jndiCtx）。这是一个需要理解的重要细节（原因稍后解释）。现在这个返回的实例用于查找 JNDI 字符串的其余部分（“app/module/distinct/bean!interface”），然后返回 EJB 代理。无论查找是在单个语句中还是在多个部分中完成，代码的工作方式都是一样的。即为 ejb: URL 字符串创建 javax.naming.Context 的实例。

那么，当这部分的标题是“如何关闭作用域 EJB 客户端上下文”时，我为什么要解释所有这些？原因是因为处理与 JNDI 上下文关联的作用域 EJB 客户端上下文的客户端应用程序会期望以下代码关闭关联的 EJB 客户端上下文，但会惊讶于它不会：

final Properties props = new Properties();
// mark it for scoped EJB client context
props.put("org.jboss.ejb.client.scoped.context","true");
// add other properties
props.put(....);
...
Context jndiCtx = new InitialContext(props);
try {
      final MyBean bean = jndiCtx.lookup("ejb:app/module/distinct/bean!interface");
      bean.doSomething();
} finally {
  jndiCtx.close();
}

应用程序期望调用 jndiCtx.close() 将有效地关闭与 JNDI 上下文关联的 EJB 客户端上下文。这不会发生，因为如前所述，支持 ejb: URL 字符串的 javax.naming.Context 与代码正在关闭的实例不同。 Java 中的 JNDI 实现只是关闭调用 close 的上下文。结果，支持 ejb: URL 字符串的另一个 javax.naming.Context 仍然没有关闭，这实际上意味着范围内的 EJB 客户端上下文也没有关闭，这最终意味着与服务器的连接EJB 客户端上下文也没有关闭。

所以现在让我们看看如何正确地做到这一点。我们知道 ejb: URL 字符串查找返回给我们一个 javax.naming.Context。我们所要做的就是保持对这个实例的引用，并在我们完成 EJB 调用时关闭它。下面是它的外观：

final Properties props = new Properties();
// mark it for scoped EJB client context
props.put("org.jboss.ejb.client.scoped.context","true");
// add other properties
props.put(....);
...
Context jndiCtx = new InitialContext(props);
Context ejbRootNamingContext = (Context) jndiCtx.lookup("ejb:");
try {
    final MyBean bean = ejbRootNamingContext.lookup("app/module/distinct/bean!interface"); // the rest of the EJB jndi string
    bean.doSomething();
} finally {
    try {
        // close the EJB naming JNDI context
        ejbRootNamingContext.close();
    } catch (Throwable t) {
        // log and ignore
    }
    try {
        // also close our other JNDI context since we are done with it too
        jndiCtx.close();
    } catch (Throwable t) {
        // log and ignore
    }

}

如您所见，我们将代码更改为首先仅查找“ejb:”字符串以获取 EJB 命名上下文，然后使用该 ejbRootNamingContext 实例查找其余 EJB JNDI 名称以获取EJB 代理。然后，当需要关闭上下文时，我们关闭了 ejbRootNamingContext（以及其他 JNDI 上下文）。关闭 ejbRootNamingContext 可确保与该 JNDI 上下文关联的作用域 EJB 客户端上下文也被关闭。实际上，这会关闭该 EJB 客户端上下文中与服务器的连接。

更多详情可以参考 Scoped EJB client contexts

【讨论】：

谢谢斯内哈尔！但我检查了我们的代码。我们没有设置 props.put("org.jboss.ejb.client.scoped.context","true");所以我认为我们没有使用 Scoped EJB Client 上下文。但我会添加 ejbRootNamingContext.close();看看我们是否可以避免这个问题。
@ChihpengLin 让我知道以防问题仍然存在。我们之前遇到过类似的问题，并在此帮助下解决了。
感谢您的帮助。当您遇到 OutOfMemory 问题时，您是否注意到 ** Remoting "endpoint" task** 线程的数量？当我们遇到这个问题时，有上千个 **Remoting “endpoint” task** 线程，但它们都在等待，什么都不做。
我们在线程转储中遇到类似的远程“端点”任务线程。你能分享你的 EJB 查找和远程执行代码吗？
这里是我们创建 InitialContext 和查找 ejb 的方法： prop.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory"); prop.put(Context.PROVIDER_URL, "http-remoting://" + ip + ":" + 端口); prop.put("jboss.naming.client.ejb.context", true);上下文 ctx = new InitialContext(prop); MyBean bean = (MyBean) ctx.lookup(jndiName);

【解决方案2】：

我发现远程“端点”任务线程是由javax.management.remote.JMXConnector创建的。我们打开了一些 javax.management.remote.JMXConnector 来访问其他服务器中的 MBean。但没有关闭它们。关闭那些 JMXConnector 实例后，线程就消失了。

javax.management.remote.JMXConnector 正在使用 xnio 与 MBean 通信。它将在打开时创建一个 XnioWorker，XnioWorker 将创建 Remoting "endpoint" task 线程。所以问题不是由 EJB 引起的。

【讨论】：