我在Eclipse中有一个项目，它上面有一个红叉，不会导出到可运行的JAR。自从我在笔记本电脑上重新安装Windows以来，我不记得是否看过它，但我知道我没有更改任何代码。任何类都没有错误，但是我得到的错误指向下面的类，它处理Mac OSx上的菜单项：
import java.lang.reflect.*;
public class osxhandler implements InvocationHandler {
protected Object targetObject;
protected Method targetMethod;
protected String proxySignature;
static Object macOSXApplication;
// Pass this method an Object and Method equipped to perform application shutdown logic
// The method passed should return a boolean stating whether or not the quit should occur
public static void setQuitHandler(Object target, Method quitHandler) {
setHandler(new HOsx("handleQuit", target, quitHandler));
}
public static void setAboutHandler(Object target, Method aboutHandler) {
boolean enableAboutMenu = (target != null && aboutHandler != null);
if (enableAboutMenu) {
setHandler(new HOsx("handleAbout", target, aboutHandler));
}
// If we're setting a handler, enable the About menu item by calling
// com.apple.eawt.Application reflectively
try {
Method enableAboutMethod = macOSXApplication.getClass().getDeclaredMethod("setEnabledAboutMenu", new Class[] { boolean.class });
enableAboutMethod.invoke(macOSXApplication, new Object[] { Boolean.valueOf(enableAboutMenu) });
} catch (Exception ex) {
System.err.println("MacOSHandler could not access the About Menu");
ex.printStackTrace();
}
}
public static void setPreferencesHandler(Object target, Method prefsHandler) {
boolean enablePrefsMenu = (target != null && prefsHandler != null);
if (enablePrefsMenu) {
setHandler(new HOsx("handlePreferences", target, prefsHandler));
}
// If we're setting a handler, enable the Preferences menu item by calling
// com.apple.eawt.Application reflectively
try {
Method enablePrefsMethod = macOSXApplication.getClass().getDeclaredMethod("setEnabledPreferencesMenu", new Class[] { boolean.class });
enablePrefsMethod.invoke(macOSXApplication, new Object[] { Boolean.valueOf(enablePrefsMenu) });
} catch (Exception ex) {
System.err.println("MacOSHandler could not access the About Menu");
ex.printStackTrace();
}
}
// Pass this method an Object and a Method equipped to handle document events from the Finder
// Documents are registered with the Finder via the CFBundleDocumentTypes dictionary in the
// application bundle's Info.plist
public static void setFileHandler(Object target, Method fileHandler) {
setHandler(new HOsx("handleOpenFile", target, fileHandler) {
// Override MacOSHandler.callTarget to send information on the
// file to be opened
public boolean callTarget(Object appleEvent) {
if (appleEvent != null) {
try {
Method getFilenameMethod = appleEvent.getClass().getDeclaredMethod("getFilename", (Class[])null);
String filename = (String) getFilenameMethod.invoke(appleEvent, (Object[])null);
this.targetMethod.invoke(this.targetObject, new Object[] { filename });
} catch (Exception ex) {
}
}
return true;
}
});
}
// setHandler creates a Proxy object from the passed MacOSHandler and adds it as an ApplicationListener
@SuppressWarnings({ "unchecked", "rawtypes" })
public static void setHandler(HOsx adapter) {
try {
Class applicationClass = Class.forName("com.apple.eawt.Application");
if (macOSXApplication == null) {
macOSXApplication = applicationClass.getConstructor((Class[])null).newInstance((Object[])null);
}
Class applicationListenerClass = Class.forName("com.apple.eawt.ApplicationListener");
Method addListenerMethod = applicationClass.getDeclaredMethod("addApplicationListener", new Class[] { applicationListenerClass });
// Create a proxy object around this handler that can be reflectively added as an Apple ApplicationListener
Object MacOSHandlerProxy = Proxy.newProxyInstance(HOsx.class.getClassLoader(), new Class[] { applicationListenerClass }, adapter);
addListenerMethod.invoke(macOSXApplication, new Object[] { MacOSHandlerProxy });
} catch (ClassNotFoundException cnfe) {
System.err.println("This version of Mac OS X does not support the Apple EAWT. ApplicationEvent handling has been disabled (" + cnfe + ")");
} catch (Exception ex) { // Likely a NoSuchMethodException or an IllegalAccessException loading/invoking eawt.Application methods
System.err.println("Mac OS X Adapter could not talk to EAWT:");
ex.printStackTrace();
}
}
// Each MacOSHandler has the name of the EAWT method it intends to listen for (handleAbout, for example),
// the Object that will ultimately perform the task, and the Method to be called on that Object
protected HOsx(String proxySignature, Object target, Method handler) {
this.proxySignature = proxySignature;
this.targetObject = target;
this.targetMethod = handler;
}
// Override this method to perform any operations on the event
// that comes with the various callbacks
// See setFileHandler above for an example
public boolean callTarget(Object appleEvent) throws InvocationTargetException, IllegalAccessException {
Object result = targetMethod.invoke(targetObject, (Object[])null);
if (result == null) {
return true;
}
return Boolean.valueOf(result.toString()).booleanValue();
}
// InvocationHandler implementation
// This is the entry point for our proxy object; it is called every time an ApplicationListener method is invoked
public Object invoke (Object proxy, Method method, Object[] args) throws Throwable {
if (isCorrectMethod(method, args)) {
boolean handled = callTarget(args[0]);
setApplicationEventHandled(args[0], handled);
}
// All of the ApplicationListener methods are void; return null regardless of what happens
return null;
}
// Compare the method that was called to the intended method when the MacOSHandler instance was created
// (e.g. handleAbout, handleQuit, handleOpenFile, etc.)
protected boolean isCorrectMethod(Method method, Object[] args) {
return (targetMethod != null && proxySignature.equals(method.getName()) && args.length == 1);
}
// It is important to mark the ApplicationEvent as handled and cancel the default behavior
// This method checks for a boolean result from the proxy method and sets the event accordingly
protected void setApplicationEventHandled(Object event, boolean handled) {
if (event != null) {
try {
Method setHandledMethod = event.getClass().getDeclaredMethod("setHandled", new Class[] { boolean.class });
// If the target method returns a boolean, use that as a hint
setHandledMethod.invoke(event, new Object[] { Boolean.valueOf(handled) });
} catch (Exception ex) {
System.err.println("MacOSHandler was unable to handle an ApplicationEvent: " + event);
ex.printStackTrace();
}
}
}
}
关于为什么我不能导出/编译的任何想法？我以前从未遇到过这个问题
只需在项目上进行清理和/或重建。
您可以在Eclipse的Project菜单下找到它。
我也有一个不同的，退化的问题。事实证明，我们的项目中有一个类有一个文件（所以Eclipse将它保存在类路径中），但文件中没有定义实际的类（文件只有导入和类注释......可能是合并错误） 。无论如何，删除文件解决了问题。
Eclipse总是在项目文件夹中生成隐藏文件.project和.classpath，这是非常可恶的。有时您不知道这些文件中是否出现问题。
在升级Eclipse之后，如果发现以下编译错误，我建议您检查项目文件夹中的.classpath。
由于构建路径不完整，因此未构建项目。找不到java.lang.Object的类文件。修复构建路径，然后尝试构建此项目
很可能你会看到像这样的一条线。
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/ org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/j2re1.4.2_03"/>
愚蠢的Eclipse无缘无故地附加了这个。只需将其删除即可再次使用。 ;）
/org.eclipse.基督徒.internal.debug.UI.launcher.standard VM type/就2热1.4.2_谢谢
资料来源：http://hochit.com/2006/07/06/eclipse-upgrading-problem-javalangobject-not-found/
另外，你可以在日食中检查你的project settings。右键单击您的项目并选择属性。转到Java Build Path，应该有更具体的问题信息。您最有可能将JDK设置为新系统上不存在的版本。
如果这也没有帮助，请选择您的项目，然后使用菜单条目Source->Clean Up。
我在这里被提到了，因为我有同样的错误。我在日食上使用maven。我右键单击repo，选择了build path-> Conifgure build-> Project References并检查了我的repo的项目引用。这对我有用。
我也得到了同样的错误。在我的情况下问题是，我曾经通过“用户库”多次将同一个jar放在同一个项目中的“构建路径”下一次。刚从类路径中删除了重复的jar并得到了上述错误。
在我的例子中，类是空的，编译器抱怨：
Class files on classpath not found or not accessible for: 'ibDemo/src/com/ib/controller/LocationCode.java'
Class files on classpath not found or not accessible for: 'ibDemo/src/com/ib/controller/PairPanel.java'
为了解决这个问题，我要添加一个类声明：
public class LocationCode
{
}
和
public class PairPanel
{
}
我有同样的错误，在尝试了多个推荐之后，没有任何结果。所以我创建了一个新工作区并参考了这个项目。之后，它成功构建并导出JAR而没有错误。
不确定这可能是最好的解决方案，但请检查java构建路径。我把它指向了一个错误的位置，因为我面对的是类找不到错误。修复java构建路径后，问题就解决了。
我是因为错误而来到这里的。在我的情况下，什么都没有编译（构建？），Eclipse并没有告诉我除了这些神秘的消息之外，构建还有任何问题。我最终解压缩了jar文件，发现它没有类。这是因为我在构建路径中引用的项目没有构建。在我的情况下，该项目不会在一百万年内编译，但我可以访问研发部门的jar文件，他们可以并且确实以自己的方式编译它。所以我引用了那些jar文件。现在我的类编译，错误就消失了。我确信我会在第一时间做到这一点但是“有用的”Eclipse建议我参考未构建的项目，所以我提出了不好的建议！