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Creating Classloader for a servlet container  RSS feed

Amitkumar Dhama
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Posts: 56
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Hi All Ranchers,

I am getting while creating classloader for my servlet container.
What I have done is that i have created a URLClassloader as bootstrap loader for all container classes.
Now whenever i try to create a new classloader for a deployed web application taking this bootstrap classloader as parent.
The web app classloader is again a URLClassloader which is gives first priorty to the classes availble in WEB-INF/classes to the WEB-INF/lib classes as shown below

final static String WEBAPP_CLASSES = "WEB-INF/classes";

final static String WEBAPP_LIB = "WEB-INF/lib";

public static ClassLoader forWebApp(File webAppDirPath) {
ClassLoader parent = Thread.currentThread().getContextClassLoader();
ClassLoader classesDirLoader = createLoader(webAppDirPath,

ClassLoader libDirLoader = createLoader(webAppDirPath, WEBAPP_LIB,

return libDirLoader;

private static URLClassLoader createLoader(File webAppDirPath,
String forDir, ClassLoader parent) {
String path;
URL urls[] = new URL[] {};
try {
path = webAppDirPath.getCanonicalPath() + "/" + forDir;
urls = createClassPathURLs(path);
} catch (IOException e) {
; // IGNORE and return not a valid path
log.error("Invalid DD path [" + webAppDirPath + "]!", e);

return new URLClassLoader(urls, parent);

private static URL[] createClassPathURLs(String path) {
URL urls[] = new URL[] {};
File webAppCls = new File(path);
if (webAppCls.exists() && webAppCls.isDirectory()) {
File conLibFiles[] = webAppCls.listFiles(new FileFilter() {
public boolean accept(File file) {
String fileName = file.getName().toLowerCase();
boolean isDir = file.isDirectory();
boolean isJar = fileName.endsWith(".jar");
boolean isZip = fileName.endsWith(".zip");
return !isDir && (isJar || isZip);

urls = new URL[conLibFiles.length + 1];
try {
urls[0] = webAppCls.toURL();
} catch (MalformedURLException e) {
; // IGNORE can't come now
for (int i = 0; i < conLibFiles.length; i++) {
try {
urls[i + 1] = conLibFiles[i].toURL();
} catch (MalformedURLException e) {
log.error("Invalid Class Path URL found [" + conLibFiles[i]
+ "]", e);
return urls;

I am facing following problem
i.e The Web APP is having a class called a.b.Test
that is available in WEB-INF/classes dir and its referring to some
other class x.y.SomeJarClass in WEB-INF/lib dir.
But a java.lang.NoClassDefFoundError: is thrown for x.y.SomeJarClass in WEB-INF/lib dir.

thanking u in advance..
Ulf Dittmer
Posts: 42972
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Please do not post the same question to several forums, like you have done here. It leads to duplicated effort, and doesn't really increase your audience. Let's continue the discussion in the other thread, since this is a servlet-related topic.
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