如何捕获事件调度线程（EDT）exception？

我正在使用一个名为MyExceptionHandler的类来实现Thread.UncaughtExceptionHandler来处理项目中的正常exception。

据我所知，这个类无法捕获EDTexception，所以我尝试在main()方法中使用它来处理EDTexception：

 public static void main( final String[] args ) { Thread.setDefaultUncaughtExceptionHandler( new MyExceptionHandler() ); // Handle normal exceptions System.setProperty( "sun.awt.exception.handler",MyExceptionHandler.class.getName()); // Handle EDT exceptions SwingUtilities.invokeLater(new Runnable() { // Execute some code in the EDT. public void run() { JFrame myFrame = new JFrame(); myFrame.setVisible( true ); } }); } 

但直到现在它还没有用。 例如，在初始化JFrame时，我从构造函数中的bundle文件加载其标签，如下所示：

 setTitle( bundle.getString( "MyJFrame.title" ) ); 

我从包文件中删除了密钥MyJFrame.title来测试exception处理程序，但它没有用！ 例外通常打印在日志中。

我在这里做错了吗？

Answer 1

EDTexception处理程序不使用Thread.UncaughtExceptionHandler 。 相反，它调用具有以下签名的方法：

 public void handle(Throwable thrown); 

将它添加到MyExceptionHandler ，它应该工作。

对此的“文档”可在EventDispatchThread找到，它是java.awt的包私有类。 从handleException()的javadoc引用：

 /** * Handles an exception thrown in the event-dispatch thread. * * 
 If the system property "sun.awt.exception.handler" is defined, then * when this method is invoked it will attempt to do the following: * * 
 * 
 Load the class named by the value of that property, using the * current thread's context class loader, * 
 Instantiate that class using its zero-argument constructor, * 
 Find the resulting handler object's public void handle * method, which should take a single argument of type * Throwable, and * 
 Invoke the handler's handle method, passing it the * thrown argument that was passed to this method. * 
 * * If any of the first three steps fail then this method will return * false and all following invocations of this method will return * false immediately. An exception thrown by the handler object's * handle will be caught, and will cause this method to return * false. If the handler's handle method is successfully * invoked, then this method will return true. This method will * never throw any sort of exception. * * 
 Note: This method is a temporary hack to work around the * absence of a real API that provides the ability to replace the * event-dispatch thread. The magic "sun.awt.exception.handler" property * will be removed in a future release. */ 

太阳如何期待你发现这一点，我不知道。

这是一个完整的示例，可以捕获EDT内外的exception：

 import javax.swing.SwingUtilities; public class Test { public static class ExceptionHandler implements Thread.UncaughtExceptionHandler { public void handle(Throwable thrown) { // for EDT exceptions handleException(Thread.currentThread().getName(), thrown); } public void uncaughtException(Thread thread, Throwable thrown) { // for other uncaught exceptions handleException(thread.getName(), thrown); } protected void handleException(String tname, Throwable thrown) { System.err.println("Exception on " + tname); thrown.printStackTrace(); } } public static void main(String[] args) { Thread.setDefaultUncaughtExceptionHandler(new ExceptionHandler()); System.setProperty("sun.awt.exception.handler", ExceptionHandler.class.getName()); // cause an exception on the EDT SwingUtilities.invokeLater(new Runnable() { public void run() { ((Object) null).toString(); } }); // cause an exception off the EDT ((Object) null).toString(); } } 

应该这样做。

Answer 2

仅仅为了一些额外的信息，在很多情况下，即使在1.5和1.6中，Throwables也会被EDT的UncaughtExceptionHandler捕获。 查看1.5.0_22中EventDispatchThread的源代码：

 private void processException(Throwable e, boolean isModal) { if (!handleException(e)) { // See bug ID 4499199. // If we are in a modal dialog, we cannot throw // an exception for the ThreadGroup to handle (as added // in RFE 4063022). If we did, the message pump of // the modal dialog would be interrupted. // We instead choose to handle the exception ourselves. // It may be useful to add either a runtime flag or API // later if someone would like to instead dispose the // dialog and allow the thread group to handle it. if (isModal) { System.err.println( "Exception occurred during event dispatching:"); e.printStackTrace(); } else if (e instanceof RuntimeException) { throw (RuntimeException)e; } else if (e instanceof Error) { throw (Error)e; } } } private boolean handleException(Throwable thrown) { try { if (handlerClassName == NO_HANDLER) { return false; /* Already tried, and failed */ } /* Look up the class name */ if (handlerClassName == null) { handlerClassName = ((String) AccessController.doPrivileged( new GetPropertyAction(handlerPropName))); if (handlerClassName == null) { handlerClassName = NO_HANDLER; /* Do not try this again */ return false; } } /* Load the class, instantiate it, and find its handle method */ Method m; Object h; try { ClassLoader cl = Thread.currentThread().getContextClassLoader(); Class c = Class.forName(handlerClassName, true, cl); m = c.getMethod("handle", new Class[] { Throwable.class }); h = c.newInstance(); } catch (Throwable x) { handlerClassName = NO_HANDLER; /* Do not try this again */ return false; } /* Finally, invoke the handler */ m.invoke(h, new Object[] { thrown }); } catch (Throwable x) { return false; } return true; } 

根据这段代码，EDT Thread的UncaughtExceptionHandler只有3种方法不会捕获Throwable：

1. Throwable由sun.awt.exception.handler成功处理（找到类，实例化并调用其句柄（Throwable）方法而不抛出任何东西）
2. EDT处于modal dialog中
3. Throwable既不是RuntimeException也不是Error

Answer 3

总结以上内容……使用较新的Java，您可以这样做：

 // Log exceptions thrown on the event dispatcher thread SwingUtilities.invokeLater(() -> Thread.currentThread().setUncaughtExceptionHandler((thread, t) -> this.log.error("exception in event dispatcher thread", t)));