Java 是否可以在gwt内调试ConcurrentModificationException

我有一个复杂的gwt应用程序，偶尔会抛出java.util.ConcurrentModificationException，但是我不知道哪个对象是问题的根源

java.util.ConcurrentModificationException
        at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)
        at java.util.ArrayList$Itr.next(ArrayList.java:859)
        at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.serialize(Collection_CustomFieldSerializerBase.java:43)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serialize(ArrayList_CustomFieldSerializer.java:39)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:51)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:28)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:788)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:669)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:130)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:153)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:587)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeClass(ServerSerializationStreamWriter.java:757)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:796)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:669)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:130)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:153)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:587)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeClass(ServerSerializationStreamWriter.java:757)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:796)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:669)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:130)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:153)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:587)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeClass(ServerSerializationStreamWriter.java:757)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:796)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:669)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:130)
        at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.serialize(Collection_CustomFieldSerializerBase.java:44)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serialize(ArrayList_CustomFieldSerializer.java:39)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:51)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:28)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:788)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:669)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:130)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:153)
        at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:587)
        at com.google.gwt.user.server.rpc.RPC.encodeResponse(RPC.java:605)
        at com.google.gwt.user.server.rpc.RPC.encodeResponseForSuccess(RPC.java:471)
        at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:563)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:265)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:305)
        at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:706)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:791)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1580)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:258)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:652)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:591)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
        at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:463)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:168)
        at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
        at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
        at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:242)
        at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
        at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
        at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
        at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
        at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
        at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
        at java.lang.Thread.run(Thread.java:748)

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是否有方法调试应用程序以确定此问题的根源？glassfish服务器在Debian上运行，客户端独立于操作系统。源代码构建在Debian系统上，然后导出到服务器以供运行时使用。因为代码中有57个对象是可序列化的，并且包含ArrayList，而这些ArrayList中的一些对象也包含嵌套的ArrayList。

这通常是由多个线程访问同一ArrayList引起的。使数组列表线程安全的最简单方法是用以下方式包装它：

List<String> list = Collections.synchronizedList(new ArrayList<String>()); 

List List=Collections.synchronizedList（新的ArrayList（））；

另一个可能的原因可能是您迭代列表并在该循环中修改列表。这有时有效，但并不总是有效。坏例子：

List<String> list = new ArrayList<String>();
// fill the list here
for (String item : list)
{
    if (item.contains("xxx"))
    {
        list.remove(item);
    }
}

List List=new ArrayList（）；
//在这里填写清单
用于（字符串项：列表）
{
如果（项目包含（“xxx”））
{
列表。删除（项目）；
}
}

使用临时列表修复此问题的示例：

List<String> list = new ArrayList<String>();
// fill the list here

List<String> toRemove = new ArrayList<String>();
for (String item : list)
{
    if (item.contains("xxx"))
    {
        toRemove=item;
    }
}
for (String item : toRemove)
{
    list.remove(item);
}

List List=new ArrayList（）；
//在这里填写清单
List toRemove=new ArrayList（）；
用于（字符串项：列表）
{
如果（项目包含（“xxx”））
{
toRemove=项目；
}
}
用于（字符串项：toRemove）
{
列表。删除（项目）；
}

理解，但问题是我如何找到50多个对象中的哪一个是罪魁祸首？客户端是单线程的，服务器端一次只运行一个作业，但是作业可以将对象提交给事件侦听器，而事件侦听器最终会进入我无法控制的http侦听器。那么，有没有办法调试java.util.ArrayList$Itr.CheckForComodition以查找对象？您确定HTTP服务器运行单线程吗？这将是非常不寻常的。它假定罪魁祸首是并发传入的HTTP请求。线程转储将显示当前正在执行的所有线程和方法。可能这有助于在发生异常时生成这样的转储：。当然，您需要以某种方式捕获异常。服务器端代码应该一次运行一个作业，而不是单线程，一个作业可能会为某些内容生成一个线程，但不会等待线程完成，它只是在完成作业时移动。然后触发队列中的下一个作业，这可能会导致另一个线程启动，依此类推。我将研究如何，但是仍然需要找到一种方法来锁定http-listener。是的，这肯定是服务器端的一个错误，当RemoteServiceServlet正在迭代其内容以将其发送到客户端时，该列表正在发生变化。发送到客户端的任何内容都不应在发送时更改，否则您可能会发送不一致的数据—或者阻止对这些对象进行编辑，或者在发送之前进行复制。