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package org.glassfish.appclient.client;
import java.io.IOException;
import java.net.URL;
import java.util.*;
/**
* {@link ClassLoader} that masks a specified set of classes
* from its parent class loader.
*
*
* This code is used to create an isolated environment.
*
* @author Jerome Dochez
*/
public class MaskingClassLoader extends ClassLoader {
private final Set punchins = new HashSet();
private final String[] multiples;
private final boolean useExplicitCallsToFindSystemClass;
public MaskingClassLoader(ClassLoader parent, Collection punchins, Collection multiples) {
this(parent, punchins, multiples, true /* use explicit calls to findSystemClass*/);
}
/**
* Creates a new masking class loader letting a set of defined packages be loaded by the parent
* classloader. Multiples packages can be specified so that only the parent package needs to
* be provided.
*
* @param parent the parent classloader to delegate actual loading from when punchin is allowed
* @param punchins list of packages allowed to be visible from the parent
* @param multiples list of parent packages allowed to be visible from the parent class loader
*/
public MaskingClassLoader(ClassLoader parent, Collection punchins, Collection multiples,
boolean useExplicitCallsToFindSystemClass) {
super(parent);
this.punchins.addAll(punchins);
this.multiples = multiples.toArray(new String[multiples.size()]);
this.useExplicitCallsToFindSystemClass = useExplicitCallsToFindSystemClass;
}
@Override
protected synchronized Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
// I do not mask java packages, and I only mask javax. stuff for now.
try {
if (useExplicitCallsToFindSystemClass) {
return findSystemClass(name);
}
} catch(ClassNotFoundException e) {
}
if (isDottedNameLoadableByParent(name)) {
return super.loadClass(name, resolve);
}
throw new ClassNotFoundException(name);
}
@Override
public URL getResource(String name) {
if (isDottedNameLoadableByParent(resourceToDotted(name))) {
return super.getResource(name);
} else {
return null;
}
}
@Override
public Enumeration getResources(String name) throws IOException {
if (isDottedNameLoadableByParent(resourceToDotted(name))) {
return super.getResources(name);
} else {
return new Enumeration() {
@Override
public boolean hasMoreElements() {
return false;
}
@Override
public URL nextElement() {
throw new NoSuchElementException();
}
};
}
}
private String resourceToDotted(String name) {
if (name.startsWith("/")) {
name = name.substring(1);
}
return name.replace("/", ".");
}
protected boolean isDottedNameLoadableByParent(final String name) {
if (!(name.startsWith("javax.") || name.startsWith("org."))) {
return true;
}
final String packageName = name.substring(0, name.lastIndexOf("."));
if (punchins.contains(packageName)) {
return true;
}
for (String multiple : multiples) {
if (name.startsWith(multiple)) {
return true;
}
}
return false;
}
}