I'm using a FileWalker to being walking from a specified folder and find all the .class files in the folder and any subsequent sub folders so I can load them using a ClassLoader then use reflection to obtain the declared fields and methods in the class.
This works totally fine for most .class files but I sometimes get a NoClassDefFoundError when trying to load a class and I think it is to do with the location of the file. I'l use an example to illustrate my problem.
If I have the below directory structure:
D:\Users\Ste\Documents\Eclipse Workspace\Project Tests\File Reader
│
├───+bin
│ ReadFile.class
│
└───+src
ReadFile.java
I give the FileWalker the starting dir of D:\Users\Ste\.....\Project Tests\File Reader and it happily finds the .class file and loads it using a ClassLoader.
However if I add a sub folder to my src and bin folders like so:
D:\Users\Ste\Documents\Eclipse Workspace\Project Tests\File Reader
│
├───+bin
│ │ ReadFile.class
│ │
│ └───+Test
│ TestClass.class
│
└───+src
│ ReadFile.java
│
└───+Test
TestClass.java
When the program tries to load TestClass.class it gives me this error
!SESSION 2013-02-28 19:54:14.495 -----------------------------------------------
eclipse.buildId=unknown
java.version=1.7.0_13
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_GB
Framework arguments: -product ste.wootten.honoursproject.product -clearPersistedState
Command-line arguments: -product ste.wootten.honoursproject.product -data D:\Users\Ste\Documents\Uni Year 3\Project\Implementation/../runtime-honoursproject.product -dev file:D:/Users/Ste/Documents/Uni Year 3/Project/Implementation/.metadata/.plugins/org.eclipse.pde.core/honoursproject.product/dev.properties -os win32 -ws win32 -arch x86_64 -consoleLog -clearPersistedState
!ENTRY org.eclipse.e4.ui.workbench 4 0 2013-02-28 19:54:27.243
!MESSAGE Unable to create class 'ste.wootten.honoursproject.mainpart.CreateMainUI' from bundle '65'
!STACK 0
org.eclipse.e4.core.di.InjectionException: java.lang.NoClassDefFoundError: TestClass (wrong name: Test/TestClass)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:63)
at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:859)
at org.eclipse.e4.core.internal.di.InjectorImpl.inject(InjectorImpl.java:111)
at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:319)
at org.eclipse.e4.core.internal.di.InjectorImpl.make(InjectorImpl.java:240)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.make(ContextInjectionFactory.java:161)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.createFromBundle(ReflectionContributionFactory.java:102)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.doCreate(ReflectionContributionFactory.java:71)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.create(ReflectionContributionFactory.java:53)
at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer.createWidget(ContributedPartRenderer.java:141)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:896)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:630)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:732)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:703)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:697)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:682)
at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.showTab(StackRenderer.java:1114)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer$1.handleEvent(LazyStackRenderer.java:67)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler$1.run(UIEventHandler.java:41)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:180)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4687)
at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:187)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:38)
at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135)
at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78)
at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39)
at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:81)
at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:58)
at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:374)
at org.eclipse.e4.ui.model.application.ui.impl.ElementContainerImpl.setSelectedElement(ElementContainerImpl.java:171)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:103)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:646)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:732)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:703)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:697)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:682)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveRenderer.processContents(PerspectiveRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:642)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:732)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:703)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:697)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:682)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.showTab(PerspectiveStackRenderer.java:103)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer$1.handleEvent(LazyStackRenderer.java:67)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler$1.run(UIEventHandler.java:41)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:180)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4687)
at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:187)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:38)
at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135)
at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78)
at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39)
at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:81)
at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:58)
at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:374)
at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:135)
at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:1)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:103)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.postProcess(PerspectiveStackRenderer.java:77)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:646)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:732)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:703)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:697)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:682)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.processContents(WBWRenderer.java:639)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:642)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:732)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:703)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:697)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:682)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:964)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:923)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
at org.eclipse.e4.ui.internal.workbench.swt.E4Application.start(E4Application.java:150)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
Caused by: java.lang.NoClassDefFoundError: TestClass (wrong name: Test/TestClass)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at ste.wootten.honoursproject.mainpart.reflection.ReflectOnClasses.visitFile(ReflectOnClasses.java:136)
at ste.wootten.honoursproject.mainpart.reflection.ReflectOnClasses.visitFile(ReflectOnClasses.java:1)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:135)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:199)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:199)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:199)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:199)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:69)
at java.nio.file.Files.walkFileTree(Files.java:2591)
at java.nio.file.Files.walkFileTree(Files.java:2624)
at ste.wootten.honoursproject.mainpart.reflection.ReflectOnClasses.startFileWalk(ReflectOnClasses.java:39)
at ste.wootten.honoursproject.mainpart.CreateMainUI.selectDirectoryAndBeginFileWalk(CreateMainUI.java:258)
at ste.wootten.honoursproject.mainpart.CreateMainUI.createInterface(CreateMainUI.java:159)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:56)
... 104 more
I have tested this out on lot's of other directories and the same problem occurs. It seems to be caused by a .class file being in sub folders but I'm not sure why.
Here is my code to walk a file system and load the .class files found:
package ste.wootten.honoursproject.mainpart.reflection;
import ste.wootten.honoursproject.mainpart.CreateMainUI;
public class ReflectOnClasses extends SimpleFileVisitor<Path> {
//Starts the file walk from a starting directory
public static void startFileWalk(String directory){
//The startingDir is the directory the user selects on the MainUI Part
Path startingDir = FileSystems.getDefault().getPath(directory, "");
//Create an instance of my FileVisitor
ReflectOnClasses reflectOnClasses = new ReflectOnClasses();
try {
//Walk the files from my startingDir using reflectOnClasses
Files.walkFileTree(startingDir, reflectOnClasses);
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("An Error Occured");
e.printStackTrace();
}
}
//Visit files and do something with them
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attr) {
//If we find a .class file get it and reflect upon it
if(file.toString().endsWith(".class")){
//String holding the files parents directory
String filesParentDir = file.getParent().toString();
//Create a File object on the root of the directory containing the class file (it's parent directory)
File parentDir = new File(filesParentDir);
try{
//Convert parentDir to URL
URL url = parentDir.toURL();
URL[] urls = new URL[]{url};
//Create a new class loader with the directory
ClassLoader cl = new URLClassLoader(urls);
//Get the name of the file with .class removed from the end so we can load it
String classToLoad = file.getFileName().toString().replace(".class", "");
//Load in the class
Class cls = cl.loadClass(classToLoad);
//Pass the name of the class to addClassToVariableTree in CreatUI so it can be added as a TreeItem
CreateMainUI.addClassToVariableTree(classToLoad);
//Do the same for addClassToMethodTree
CreateMainUI.addClassToMethodTree(classToLoad);
//Array of the declared fields in the class
Field[] fieldsInClass = cls.getDeclaredFields();
//For each field in fieldsInClass we add it as a TreeItem using addVariableToClassTreeItem
for( Field field: fieldsInClass){
CreateMainUI.addVariableToClassNameTreeItem(field.getGenericType().toString(), field.getName());
}
//Array of all methods in the class
Method[] methodsInClass = cls.getDeclaredMethods();
//For each method we pass through the string representation of it, the class it belongs too and it's name. It will be formatted in CreateUI
for (Method method : methodsInClass) {
CreateMainUI.addMethodToClassNameTreeItem(method.toString(), classToLoad, method.getName());
}
} catch (MalformedURLException e) {
System.out.println("URL BAD");
} catch (ClassNotFoundException e){
System.out.println("Class couldnt be found");
}
}
return CONTINUE;
}
//Print out each directory visited
@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
//System.out.format("Directory: %s%n", dir);
return CONTINUE;
}
//If there is some error accessing the file, let the user know.
//If you don't override this method an error occurs, an IOException is thrown
@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) {
System.err.println(exc);
return CONTINUE;
}
}
