Java 如何捕获事件调度线程(EDT)异常?
我正在使用一个名为Java 如何捕获事件调度线程(EDT)异常?,java,exception,try-catch,event-dispatch-thread,Java,Exception,Try Catch,Event Dispatch Thread,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异常 据我所知,该类无法捕获EDT异常,因此我尝试在main()方法中使用它来处理EDT异常: public static void main( final String[] args ) { Thread.setDefaultUncaughtExceptionHandler( new MyExceptionHandler() ); // Ha
MyExceptionHandler
的类来实现Thread.UncaughtExceptionHandler
来处理项目中的正常异常
据我所知,该类无法捕获EDT异常,因此我尝试在main()
方法中使用它来处理EDT异常:
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 );
}
});
}
但直到现在它还不起作用。例如,在初始化JFrame时,我从构造函数中的捆绑文件加载其标签,如下所示:
setTitle( bundle.getString( "MyJFrame.title" ) );
我从bundle文件中删除了keyMyJFrame.title
,以测试异常处理程序,但它不起作用!异常通常打印在日志中
我在这里做错了什么吗?EDT异常处理程序没有使用
线程.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中,它应该可以工作
这方面的“文档”可以在EventDispatchThread
中找到,它是java.awt
中的包私有类。从javadoc中引用handleException()
此处:
/**
* Handles an exception thrown in the event-dispatch thread.
*
* <p> If the system property "sun.awt.exception.handler" is defined, then
* when this method is invoked it will attempt to do the following:
*
* <ol>
* <li> Load the class named by the value of that property, using the
* current thread's context class loader,
* <li> Instantiate that class using its zero-argument constructor,
* <li> Find the resulting handler object's <tt>public void handle</tt>
* method, which should take a single argument of type
* <tt>Throwable</tt>, and
* <li> Invoke the handler's <tt>handle</tt> method, passing it the
* <tt>thrown</tt> argument that was passed to this method.
* </ol>
*
* If any of the first three steps fail then this method will return
* <tt>false</tt> and all following invocations of this method will return
* <tt>false</tt> immediately. An exception thrown by the handler object's
* <tt>handle</tt> will be caught, and will cause this method to return
* <tt>false</tt>. If the handler's <tt>handle</tt> method is successfully
* invoked, then this method will return <tt>true</tt>. This method will
* never throw any sort of exception.
*
* <p> <i>Note:</i> 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
* <i>will be removed</i> in a future release.
*/
这应该就可以了。只是为了获得一些额外的信息,在许多情况下,即使在1.5和1.6版本中,EDT的UncaughtExceptionHandler也会捕捉到一次性垃圾。查看1.5.022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线程的UncaughtExceptionHandler只有3种方式不会捕获可丢弃文件:
综上所述。。。使用较新的Java,您只需执行以下操作:
// Log exceptions thrown on the event dispatcher thread
SwingUtilities.invokeLater(()
-> Thread.currentThread().setUncaughtExceptionHandler((thread, t)
-> this.log.error("exception in event dispatcher thread", t)));
@乌克尔曼。。。我照你说的做了,但没有发现异常情况。。。public void handle(Throwable抛出){System.out.println(“捕获异常”);//dod bot print!}@Brad:“即使句柄(…)不存在,异常也将由实现的方法uncaughtException(…)处理,那么就不需要句柄(…)!”这是错误的。EDT上的未捕获异常永远不会转到线程。未捕获异常处理程序,因为EDT不是常规线程。如果您的异常在示例中的异常处理程序中都没有采用这两条路径,那么您就没有未捕获的异常——它正在某个地方被捕获。@uckelman。。。在调查了我的密码后,你是对的。我代码中的一部分捕获了EDT异常。但是对于handle(…)方法,它不是必需的。仅设置系统属性就足够了:system.setProperty(“sun.awt.exception.handler”,MyExceptionHandler.class.getName())。。。我敢肯定。我已经创建了一个完整的样本来测试它。你也可以试试这个。非常感谢您的帮助。@Brad:我想自从上次查看以来,
java.awt.EventDispatchThread
中发生了一些变化,即,processException()
如果handleException()
返回false,则返回异常,如果您没有handle()
方法,该方法位于使用sun.awt.exception.handler
属性指定的处理程序中。因此,至少在Java 6的当前版本中,我想您可以只使用线程.UncaughtExceptionHandler
。知道这一点很好,但在旧版本的Java中可能无法正常工作。我可以确认在Java7中不需要handle()
方法,我们也无法在Javadoc中找到它的任何痕迹。多亏了你们两位,我现在可以正确地记录未捕获的异常了!:)但是,异常跟踪仍在stderr上打印。有没有办法避免这种情况?可能的重复
// Log exceptions thrown on the event dispatcher thread
SwingUtilities.invokeLater(()
-> Thread.currentThread().setUncaughtExceptionHandler((thread, t)
-> this.log.error("exception in event dispatcher thread", t)));