BlockingQueue 失去了它的引用并抛出 NullPointerException onMessage Jetty WebSocket
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【中文标题】BlockingQueue 失去了它的引用并抛出 NullPointerException onMessage Jetty WebSocket【英文标题】：BlockingQueue loses its reference and throws NullPointerException onMessage Jetty WebSocket 【发布时间】：2021-06-26 21:33:12 【问题描述】：不得不问这个问题，因为它已经一天试图解决问题并且无法解决。
我正在使用 Netbeans 8.2 和 java 8。
拓扑：
-
浏览器上的 WebSocket 客户端
Jetty WebSocket 服务器（带有 swing GUI 的 java 应用）
目标：将数据从客户端发送到服务器，并在 JTextArea (GUI) 上显示数据
Main.java (GUI)
public class Main extends javax.swing.JPanel
private WebSocketSwing websocketserver;
private BlockingQueue<String> stack = new ArrayBlockingQueue<String>(3);
public Main()
initComponents();
// WebSocketServer
websocketserver = new WebSocketSwing(stack);
websocketserver.start();
consumer.start();
Thread consumer = new Thread(new Runnable()
@Override
public void run()
try
String msg;
//consuming messages until exit message is received
while((msg = stack.take()) !="exit")
Thread.sleep(10);
System.out.println("Consumed: " + msg);
catch(InterruptedException e)
e.printStackTrace();
);
private void initComponents()
//GUI code goes here
public static void main(String[] args)
JFrame frame = new JFrame("Main GUI");
java.awt.EventQueue.invokeLater(new Runnable()
public void run()
frame.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
frame.getContentPane().add(new SDG());
frame.pack();
frame.setVisible(true);
);
private javax.swing.JLabel jLabel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea txt_area;
WebSocketSwing 类
public class WebSocketSwing extends Thread
/**
* @param args the command line arguments
*/
private BlockingQueue<String> stack;
public WebSocketSwing(BlockingQueue<String> queue)
this.stack = queue;
@Override
public void run()
super.run();
try
Server server = new Server(2014);
WSHandler mHandler = new WSHandler();
mHandler.SetStack(stack);
server.setHandler(mHandler);
server.setStopTimeout(0);
server.start();
//
server.join();
catch (Exception e)
e.printStackTrace();
WSHandler 类
@WebSocket
public class WSHandler extends WebSocketHandler
private Session session;
public BlockingQueue<String> stack = new ArrayBlockingQueue<String>(3); // **THIS instantiation should not be needed...**
private static ArrayList<WSHandler> sessions = new ArrayList<WSHandler>();
public static ArrayList<WSHandler> getAllSessions()
return sessions;
/*WSHandler(BlockingQueue<String> stack) // **I tried to send/assign the queue from the constructor but the method is not overridable**
SetStack(stack); // or this.stack = stack;
*/
public void SetStack(BlockingQueue<String> queue)
this.stack = queue;
//Testing operations to see the reference to the queue was successfully passed
System.out.println(stack.remainingCapacity());
stack.offer("Something"); //**consumes just fine in the other Thread...**
@OnWebSocketClose
public void onClose(int StatusCode, String reason)
sessions.remove(this);
System.out.println("Close: Status Code: " + StatusCode + ", reason: " + reason + ", sessions = " + sessions.size());
@OnWebSocketError
public void onError(Throwable t)
System.out.println("Error: " + t.getMessage());
@OnWebSocketConnect
public void onConnect(Session localSession)
session = localSession;
sessions.add(this);
System.out.println("Connect: " + session.getRemoteAddress().getAddress());
@OnWebSocketMessage
public void onMessage(String message)
try
System.out.println("Message: " + message);
session.getRemote().sendString("ACK");
SetData(message);
if(message.equals("exit"))
System.out.println("Message: Bye!...");
System.exit(0);
catch (IOException ex)
Logger.getLogger(WSHandler.class.getName()).log(Level.SEVERE, null, ex);
private void SetData(String message)
try
if (stack.offer(message))
System.out.print("Inserted");
else
System.out.print("NOT Inserted");
catch(NullPointerException e)
e.printStackTrace();
@Override
public void configure(WebSocketServletFactory factory)
factory.register(WSHandler.class);
结果> 似乎 this.stack 失去了对队列的引用... 好像我没有在类内初始化 BlockingQueue 会在 SetStack 方法之外抛出 NPE...
跟踪（当我没有在 WSHandler 类上初始化 BlockingQueue 时） 如果我的理解是正确的，如果 Main 类的引用已正确传递，我应该不需要在 Handler 中初始化 BlockingQueue ......那么我认为这就是要解决的问题......
NullPointerException 被抛出是因为对象丢失了它的引用（它在 SetStack 方法中拥有的那个......）... 这个原因是我无法做到的找到...
2021-06-26 15:35:41.990:INFO::Thread-2: Logging initialized @470ms to org.eclipse.jetty.util.log.StdErrLog
3
2021-06-26 15:35:42.077:INFO:oejs.Server:Thread-2: jetty-9.4.42.v20210604; built: 2021-06-04T17:33:38.939Z; git: 5cd5e6d2375eeab146813b0de9f19eda6ab6e6cb; jvm 1.8.0_111-b14
Consumed: Something
2021-06-26 15:35:42.827:INFO:oejs.AbstractConnector:Thread-2: Started ServerConnector@98f7e6fHTTP/1.1, (http/1.1)0.0.0.0:2014
2021-06-26 15:35:42.830:INFO:oejs.Server:Thread-2: Started @1314ms
Connect: /127.0.0.1
Message: sample message
Happened
java.lang.NullPointerException
at websocketswing.WSHandler.SetData(WSHandler.java:100)
at websocketswing.WSHandler.onMessage(WSHandler.java:78)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.jetty.websocket.common.events.annotated.CallableMethod.call(CallableMethod.java:70)
at org.eclipse.jetty.websocket.common.events.annotated.OptionalSessionCallableMethod.call(OptionalSessionCallableMethod.java:72)
at org.eclipse.jetty.websocket.common.events.JettyAnnotatedEventDriver.onTextMessage(JettyAnnotatedEventDriver.java:301)
at org.eclipse.jetty.websocket.common.message.SimpleTextMessage.messageComplete(SimpleTextMessage.java:69)
at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.appendMessage(AbstractEventDriver.java:67)
at org.eclipse.jetty.websocket.common.events.JettyAnnotatedEventDriver.onTextFrame(JettyAnnotatedEventDriver.java:287)
at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.incomingFrame(AbstractEventDriver.java:152)
at org.eclipse.jetty.websocket.common.WebSocketSession.incomingFrame(WebSocketSession.java:326)
at org.eclipse.jetty.websocket.common.extensions.AbstractExtension.nextIncomingFrame(AbstractExtension.java:148)
at org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension.nextIncomingFrame(PerMessageDeflateExtension.java:111)
at org.eclipse.jetty.websocket.common.extensions.compress.CompressExtension.forwardIncoming(CompressExtension.java:169)
at org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension.incomingFrame(PerMessageDeflateExtension.java:90)
at org.eclipse.jetty.websocket.common.extensions.ExtensionStack.incomingFrame(ExtensionStack.java:202)
at org.eclipse.jetty.websocket.common.Parser.notifyFrame(Parser.java:225)
at org.eclipse.jetty.websocket.common.Parser.parseSingleFrame(Parser.java:259)
at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onFillable(AbstractWebSocketConnection.java:459)
at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onFillable(AbstractWebSocketConnection.java:440)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)
at org.eclipse.jetty.io.ChannelEndPoint$1.run(ChannelEndPoint.java:104)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:338)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:315)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:173)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.produce(EatWhatYouKill.java:137)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:882)
at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1036)
at java.lang.Thread.run(Thread.java:745)
跟踪（初始化队列时）
2021-06-26 15:39:36.821:INFO::Thread-2: Logging initialized @470ms to org.eclipse.jetty.util.log.StdErrLog
3
2021-06-26 15:39:36.889:INFO:oejs.Server:Thread-2: jetty-9.4.42.v20210604; built: 2021-06-04T17:33:38.939Z; git: 5cd5e6d2375eeab146813b0de9f19eda6ab6e6cb; jvm 1.8.0_111-b14
Consumed: Something
2021-06-26 15:39:37.961:INFO:oejs.AbstractConnector:Thread-2: Started ServerConnector@358d4f07HTTP/1.1, (http/1.1)0.0.0.0:2014
2021-06-26 15:39:37.964:INFO:oejs.Server:Thread-2: Started @1615ms
Connect: /127.0.0.1
Message: sample message
Happened
Inserted
Message: sample message
Happened
NOT Inserted
Message: sample message
Happened
NOT Inserted
因此，我假设队列丢失了它的引用，因为“这个队列”永远不会被消费者线程消耗（就像它在第一次分配中所做的那样）
希望有人能看到我没有看到的东西......
最好的问候，
【问题讨论】：
更新了问题，如果您重新打开它，将不胜感激...谢谢 @Andrew 使用每个 websocket 连接创建一个新的 WSHandler（因为您的configure() 方法如何注册它）。重构您的代码，在您的configure() 中使用自定义WebSocketCreator，并为每个新的websocket 连接使用一个新类。请参阅先前答案中的选项 2，例如 - ***.com/questions/15646213/…
@JoakimErdfelt 非常感谢！真的！......这就是我所缺少的......这是使用自定义构造函数创建 WebSocket 的正确方法......伙计，真的只有上帝知道你帮助了我多少。再次感谢:)
【参考方案1】：
一个新的WSHandler 实例会随着您在configure() 方法中的注册方式而随着每个新的（并接受/升级的）WebSocket 连接而创建...
@Override
public void configure(WebSocketServletFactory factory)
factory.register(WSHandler.class);
重构你的代码。
首先将 WSHandler 与 WebSocket 端点分开。
使新的MyEndpoint 为您的queue 对象提供一个构造函数（或设置器）。
@WebSocket
public class MyEndpoint
private .... queue;
public MyEndpoint(... queue)
this.queue = queue;
@OnWebSocketMessage
public void onMessage(String str)
this.queue.offer(str);
接下来，您要创建一个您自己设计的自定义 org.eclipse.jetty.websocket.servlet.WebSocketCreator，它会创建 WebSocket 端点实例、填充它，然后将其交回给 Jetty 实现。
public static class MyWebSocketCreator implements WebSocketCreator
private ... masterQueue = new ...;
@Override
public Object createWebSocket(ServletUpgradeRequest req, ServletUpgradeResponse resp)
return new MyEndpoint(masterQueue);
最后，你想让你的 configure() 方法使用这个新的创建者。
@Override
public void configure(WebSocketServletFactory factory)
factory.setCreator(new MyWebSocketCreator());
这在我之前的答案选项 2 中有所介绍，How do I access instantiated WebSockets in Jetty 9?
【讨论】：
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