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Class being found by classloader but NoClassDefFoundError on newInstance() method

Class being found by classloader but NoClassDefFoundError on newInstance() method

Class being found by classloader but NoClassDefFoundError on newInstance() method

Hello Friends,
I have an junit testcase that tests a eclipse application with a very long classpath and this can't be executed in Eclipse because of Windows classpath limitations. So I decided to write a program that will execute the the JUnit Test. I create my own classloader that takes the long classpath as url and then from the classpath create "org.junit.runner.JUnitCore" and create a new instance from this class. I can load the class without any problem but as soon as I try to instantiate an object of this class I get a NoClassDefFoundError. Here is the code:

package test.com.ebay.app.rtm.biz;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;

public class RunJUnitTests {
private String classPath = "C:\\Unzips\\jmockit-1.1\\jmockit\\jmockit.jar;C:\\maven.repo\\sasurendran\\ebox\\junit\\junit\\4.11\\junit-4.11.jar;... Very long classpath";
* @param args
public static void main(String[] args) {

RunJUnitTests runJUnitTests = new RunJUnitTests();
private void doWork() {
URLClassLoader ucl = new URLClassLoader(getClassPathAsURLs(classPath));
System.out.println("UCL:" + ucl.toString());
JUnitThread runJUnitTests = new JUnitThread(ucl);
Thread t = new Thread(runJUnitTests);

private void printClassPath(URL[] urls){
for(URL url:urls)

public URL[] getClassPathAsURLs(String classpath) {
List<URL> urlList = new ArrayList<URL>();
for(String path : classpath.split(";")){
try {
urlList.add(new File(path).toURI().toURL());
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
return urlList.toArray(new URL[]{});



This is the thread class which uses the custom class loader I created:

package test.com.ebay.app.rtm.biz;

import java.net.URLClassLoader;

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class JUnitThread implements Runnable {

URLClassLoader ucl;

public JUnitThread(URLClassLoader cl){
ucl = cl;

public void run() {
try {
Class<JUnitCore> clz = (Class<JUnitCore>) ucl.loadClass("org.junit.runner.JUnitCore");
System.out.println("Loaded class : " + clz.getName());
//Object obj = clz.newInstance();
//JUnitCore junit = (JUnitCore)obj;
JUnitCore junit = clz.newInstance();
System.out.println("Thread CL:" + Thread.currentThread().getContextClassLoader().toString());
Result result = junit.runClasses(RtmCampaignSelectorTest.class);
for (Failure failure : result.getFailures()) {
} catch (InstantiationException e) {
// TODO Auto-generated catch block
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
} catch (ClassNotFoundException e) {




Output of the code:

Loaded class : org.junit.runner.JUnitCore<br>
Exception in thread "Thread-0" java.lang.NoClassDefFoundError: org/junit/runner/JUnitCore
at test.com.ebay.app.rtm.biz.JUnitThread.run(JUnitThread.java:25)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassNotFoundException: org.junit.runner.JUnitCore
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 2 more

As you can see the ClassLoader is able to find the class but not able to instantiate it from jar file 'jar:file:/C:/maven.repo/sasurendran/ebox/junit/junit/4.11/junit-4.11.jar' but not able to create a newInstance of it. Could you please help me?


RE: Class being found by classloader but NoClassDefFoundError on newInstance() method

Nice article on NoClassDefFoundError

If you're sure the jar is in the classpath, I'd check it's the same version you used to compile.

Tip: To avoid long classpaths, you can try to copy all of them to a folder like c:\jar\ so it will get shorter and you can test it


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