com.sun.enterprise.loader.ResourceLocator Maven / Gradle / Ivy
/*
* Copyright (c) 2022 Eclipse Foundation and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package com.sun.enterprise.loader;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* This class covers the resource loading rules of GlassFish.
*
* - Some resources can be overriden by the application (ie. services)
*
- Some applications may use the
delegate attribute to prioritize their classloader
* over server's own resources.
*
*
* @author David Matejcek
*/
public class ResourceLocator {
private static final Logger LOG = Logger.getLogger(ResourceLocator.class.getName());
private final URLClassLoader classLoader;
private final ClassLoader delegate;
private final boolean prioritizeDelegate;
/**
* @param classLoader - current classloader used
* @param delegate - delegate classloader, usually parent or system classloader
* @param prioritizeDelegate - true if the delegate should be used first. This rule is not
* applied for explicitly named resources which not only have higher priority than
* delegate's but they do override them. If they are present in current classloader,
* the delegate is then not used.
*/
public ResourceLocator(URLClassLoader classLoader, ClassLoader delegate, boolean prioritizeDelegate) {
this.classLoader = classLoader;
this.delegate = delegate;
this.prioritizeDelegate = prioritizeDelegate;
}
/**
* @param name
* @return true if the resource present in the current classloader can shadow parent's resource.
*/
public boolean isOverridableResource(String name) {
if ("META-INF/services/jakarta.json.spi.JsonProvider".equals(name)) {
return true;
}
return false;
}
/**
* Finds resources with the given name and returns enumeration providing their locations.
*
* @param name
* @return {@link Enumeration} of {@link URL}s
* @throws IOException
*/
public Enumeration getResources(String name) throws IOException {
LOG.log(Level.FINEST, "getResources({0})", name);
@SuppressWarnings("unchecked")
final Enumeration[] enums = new Enumeration[2];
final Enumeration localResources = classLoader.findResources(name);
if (localResources.hasMoreElements() && isOverridableResource(name)) {
return localResources;
}
final Enumeration delegateResources = delegate.getResources(name);
if (prioritizeDelegate) {
enums[0] = delegateResources;
enums[1] = localResources;
} else {
enums[1] = delegateResources;
enums[0] = localResources;
}
return new Enumeration<>() {
int index = 0;
private boolean next() {
while (index < enums.length) {
if (enums[index] != null && enums[index].hasMoreElements()) {
return true;
}
index++;
}
return false;
}
@Override
public boolean hasMoreElements() {
return next();
}
@Override
public URL nextElement() {
if (!next()) {
throw new NoSuchElementException();
}
return enums[index].nextElement();
}
};
}
}