7

我们最近从 Update 21 更新到 Java 7 Update 25，现在在从 rmi 线程调用 SwingUtilities.isEventDispatchThread() 时遇到空指针异常，因为 AppContext.getAppContext() 返回 null。

java.lang.NullPointerException at sun.awt.SunToolkit.getSystemEventQueueImplPP(Unknown Source) at sun.awt.SunToolkit.getSystemEventQueueImplPP(Unknown Source) at sun.awt.SunToolkit.getSystemEventQueueImpl(Unknown Source) at java.awt.Toolkit.getEventQueue( Unknown Source) at java.awt.EventQueue.isDispatchThread(Unknown Source) at javax.swing.SwingUtilities.isEventDispatchThread(Unknown Source) at ... ... sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect .NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source) at sun .rmi.transport.Transport$1.run（未知来源）在 sun.rmi.transport.Transport$1。在 sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.的 java.security.AccessController.doPrivileged(Native Method) 上运行(Unknown Source)。 rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java. util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)run0(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(未知来源）在 java.lang.Thread.run（未知来源）run0(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(未知来源）在 java.lang.Thread.run（未知来源）

此错误仅在 web 启动时出现，当我们通过 IDE 运行我们的应用程序时，它很好。

有没有其他人遇到过这个？知道有关 AppContext 的最新更新中发生了什么变化吗？

似乎其他人在更新后与 AppContext 有一些相关的问题： https ://forums.oracle.com/message/11077767#11077767

4

3 回答 3

1

Java3D 作为 Java Web Start 运行时，我遇到了同样的问题。我找到了另一种解决方案。您必须准备自己的 InvokeLaterProcessor 和可运行队列。它必须扩展 Thread 并获取可运行对象并在 run 方法中处理它们：

public class InvokeLaterProcessor extends Thread {

  private BlockingQueue<Runnable> queue=new ArrayBlockingQueue<Runnable>(1);

  public InvokeLaterProcessor(String name) {
    super(name);
  }

  public void invokeLater(Runnable runnable) {
    try {
      queue.put(runnable);
    } catch (InterruptedException ex) {
      log.warn("invokeLater interrupted");
    }
  }

  public void run() {
    Runnable runnable=null;
    do {
      try {
        runnable = queue.take();
        SwingUtilities.invokeLater(runnable);
      } catch (InterruptedException ex) {
        runnable=null;
      }
    } while(runnable!=null);
  }
}

您所要做的就是在主线程中创建的某个类的静态中创建它：

static {
  invokeLaterProcessor=new InvokeLaterProcessor("MyInvokeLater");
  invokeLaterProcessor.start();
}

并通过此代码处理可运行文件：

invokeLaterProcessor.invokeLater(runnable);

你不需要专有的

sun.awt.SunToolkit.invokeLaterOnAppContext(evtContext, rn)
于 2013-08-01T14:42:48.210 回答
0

这是 JDK-8019274 的解决方法，打包在实用程序类中。

对我们来说，invokeAndWait()这是个大问题。此示例具有针对 的现有修复invokeLater()和针对 的新修复invokeAndWait()。

笔记：

  • 你需要 jnlp.jar
  • 在调用之前，init()在您的main()方法中尽早调用invokeLater()！
  • invokeLater()用invokeAndWait()这些调用替换所有调用

（免责声明：这是来自我们的产品。此解决方案的某些方面可能不适用于您。）

public class JreFix {
    private static String badVersionInfo = null;
    private static AppContext awtEventDispatchContext = null;
    private static AppContext mainThreadContext = null;
    private static Boolean isWebStart = null;
    private static BasicService basicService = null;
    private static IntegrationService integrationService = null;

    /**
     * Call this early in main().  
     */
    public static void init() {
        if (isWebstart() && isApplicableJvmType()) {
            String javaVersion = System.getProperty("java.version");

            if ("1.7.0_25".equals(javaVersion)) {
                badVersionInfo = "7u25";
            }
            else if ("1.7.0_40".equals(javaVersion)) {
                badVersionInfo = "7u40";
            }
            else if (javaVersion != null && "1.6.0_51".equals(javaVersion.substring(0,8))) {
                badVersionInfo = "6u51";
            }
            else if ("javaws-10.25.2.16".equals(System.getProperty("javawebstart.version"))) {
                badVersionInfo = "Web Start 10.25.2.16";
            }
        }

        if (badVersionInfo != null) {
            mainThreadContext = AppContext.getAppContext();
            try {
                SwingUtilities.invokeAndWait(new Runnable() {
                    public void run() {
                        awtEventDispatchContext = AppContext.getAppContext();
                    }
                });
            }
            catch (Exception e) {
                displayErrorAndExit(null);
            }

            if (mainThreadContext == null || awtEventDispatchContext == null) {
                 displayErrorAndExit(null);
            }
        }
    }

    public static void invokeNowOrLater(Runnable runnable) {
        if (hasAppContextBug()) {
            invokeLaterOnAwtEventDispatchThreadContext(runnable);
        }
        else {
            SwingUtilities.invokeLater(runnable);
        }
    }

    public static void invokeNowOrWait(Runnable runnable) {
        if (hasAppContextBug()) {
            fixThreadAppContext(null);
        }

        try {
            SwingUtilities.invokeAndWait(runnable);
        } 
        catch (Exception e) {
            // handle it
        }
    }

    public static boolean hasAppContextBug() {
        return isJreWithAppContextBug() && AppContext.getAppContext() == null;
    }

    public static void invokeLaterOnAwtEventDispatchThreadContext(Runnable runnable) {
        sun.awt.SunToolkit.invokeLaterOnAppContext(awtEventDispatchContext, runnable);
    }

    public static void fixThreadAppContext(Component parent) {
        try {
            final Field field = AppContext.class.getDeclaredField("threadGroup2appContext");
            field.setAccessible(true);
            Map<ThreadGroup, AppContext> threadGroup2appContext = (Map<ThreadGroup, AppContext>)field.get(null);
            final ThreadGroup currentThreadGroup = Thread.currentThread().getThreadGroup();
            threadGroup2appContext.put(currentThreadGroup, mainThreadContext);
        } 
        catch (Exception e) {
            displayErrorAndExit(parent);
        }

        if (AppContext.getAppContext() == null) {
             displayErrorAndExit(parent);
        }
    }

    private static boolean isJreWithAppContextBug() {
        return badVersionInfo != null;
    }

    private static void displayErrorAndExit(Component parent) {
        JLabel msgLabel = new JLabel("<html>" + 
                "Our application cannot run using <b>Web Start</b> with this version of Java.<p><p>" +
                "Java " + badVersionInfo + " contains a bug acknowledged by Oracle (JDK-8019274).");
        JOptionPane.showMessageDialog(parent, msgLabel, "Java Version Error", JOptionPane.ERROR_MESSAGE);
        System.exit(1);
    }

    private static boolean isApplicableJvmType() {
        String vendor = System.getProperty("java.vendor");
        String vmName = System.getProperty("java.vm.name");
        if (vendor != null && vmName != null) {
            return vmName.contains("Java HotSpot") &&
                    (vendor.equals("Oracle Corporation") || 
                     vendor.equals("Sun Microsystems Inc."));
        }

        return false;
    }

    private static boolean isWebstart() {
        if (isWebStart == null) {
            try { 
                basicService = (BasicService) ServiceManager.lookup("javax.jnlp.BasicService");             
                isWebStart = true;
            } 
            catch (UnavailableServiceException e) { 
                isWebStart = false;
            }           

            try {
                integrationService = (IntegrationService) ServiceManager.lookup("javax.jnlp.IntegrationService");
            } 
            catch (UnavailableServiceException e) {
            }
        }
        return isWebStart;
    }
}
于 2013-09-27T15:12:26.003 回答
0

这不是最终答案，但它是一种解决方法，对我有用。

应用程序需要将当前的 AppContext 保存在 EVT 中：

  AppContext evtContext; //field

  SwingUtilities.invokeLater(new Runnable() {
      public void run() {
          evtContext = AppContext.getAppContext();
      }
  });

然后所有来自 RMI 线程的调用都SwingUtilities.invokeLater(..)必须替换为invokeLater2(Runnable rn)使用如下的自定义方法sun.awt.SunToolkit.invokeLaterOnAppContext(..,..)：

void invokeLater2(Runnable rn) {
    if (AppContext.getAppContext() == null) {
        logger.warning("AppContext is null, using EVT AppContext"
          + " through SunToolKit");
        sun.awt.SunToolkit.invokeLaterOnAppContext(evtContext, rn);
    } else {
        SwingUtilities.invokeLater(rn);
    }
}

不幸的是，必须替换从 RMI 线程对 SwingUtilities.invokeLater(..) 的所有调用，并且程序现在依赖于内部 Sun JRE 专有 API。

我希望 Oracle 能尽快为 JRE 1.7.0.u25 提供补丁来解决这个问题。

- 此解决方法是根据此处guruman评论中的建议提出的。

于 2013-06-25T15:39:08.273 回答