UncaughtExceptionHandler 未捕获某些异常

Question

我创建了一个 UncaughtExceptionHandler，如 本文。

我还注册了这个处理程序来捕获所有线程中的异常，如下所示：

    Thread.setDefaultUncaughtExceptionHandler(new MyExceptionHandler());

但是，它缺少一些异常：

Exception occurred during event dispatching:
java.lang.RuntimeException: Critical error!
    at com.acme.MyClass.myMethod(MyClass.java:46)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
    at java.awt.EventQueue.access$000(EventQueue.java:84)
    at java.awt.EventQueue$1.run(EventQueue.java:602)
    at java.awt.EventQueue$1.run(EventQueue.java:600)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
    at java.awt.Dialog$1.run(Dialog.java:1046)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
    at java.awt.EventQueue.access$000(EventQueue.java:84)
    at java.awt.EventQueue$1.run(EventQueue.java:602)
    at java.awt.EventQueue$1.run(EventQueue.java:600)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
    at java.awt.EventQueue$2.run(EventQueue.java:616)
    at java.awt.EventQueue$2.run(EventQueue.java:614)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

为什么它缺少这样的异常？

Answer 1

抛出此异常的线程可能已经有自己的未捕获异常处理程序。在这种情况下，不使用默认处理程序。您可以通过调用相关线程（此处为事件调度程序线程）上的 getUncaughtExceptionHandler() 方法来检查这一点。

也可能该线程属于一个特殊的ThreadGroup，它处理异常而不是将其委托给默认处理程序。

在这两种情况下，您都可以使用 setUncaughtExceptionHandler() 方法将您的处理程序显式设置为该线程的处理程序。

Answer 2

java.awt.EventDispatchThread#processException 关心 sun.awt.exception.handler 系统属性。据报道，这个 bug 已在 Java 7 中修复。

对于 Java 6，下一步是非常适合我：

import java.lang.Thread.UncaughtExceptionHandler;

import org.apache.log4j.Logger;

/**
 * @see java.awt.EventDispatchThread.processException
 * @see java.lang.Thread.dispatchUncaughtException
 * @see java.lang.ThreadGroup.uncaughtException
 * @author Mykhaylo Adamovych
 */
public class DefaultUncaughtExceptionHandler implements UncaughtExceptionHandler {
    public static final String SP_SUN_AWT_EXCEPTION_HANDLER = "sun.awt.exception.handler";
    static {
        if (Thread.getDefaultUncaughtExceptionHandler() == null)
            Thread.setDefaultUncaughtExceptionHandler(new DefaultUncaughtExceptionHandler());
        if (System.getProperty(SP_SUN_AWT_EXCEPTION_HANDLER) == null)
            System.setProperty(SP_SUN_AWT_EXCEPTION_HANDLER, DefaultUncaughtExceptionHandler.class.getName());
    }
    
    public static void initialize() {
        // load class and perform initialization
    }
    
    public void handle(Throwable e) {
        uncaughtException(Thread.currentThread(), e);
    }
    
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        if (!(e instanceof ThreadDeath))
            Logger.getLogger(e.getStackTrace()[0].getClassName()).error("Exception in thread \"" + t.getName() + "\"", e);
    }
}