com.redhat.ceylon.langtools.tools.javac.util.CloseableURLClassLoader Maven / Gradle / Ivy
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.redhat.ceylon.langtools.tools.javac.util;
import java.io.Closeable;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.jar.JarFile;
/**
* A URLClassLoader that also implements Closeable.
* Reflection is used to access internal data structures in the URLClassLoader,
* since no public API exists for this purpose. Therefore this code is somewhat
* fragile. Caveat emptor.
* @throws Error if the internal data structures are not as expected.
*
* This is NOT part of any supported API.
* If you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.
*/
public class CloseableURLClassLoader
extends URLClassLoader implements Closeable {
public CloseableURLClassLoader(URL[] urls, ClassLoader parent) throws Error {
super(urls, parent);
try {
getLoaders(); //proactive check that URLClassLoader is as expected
} catch (Throwable t) {
throw new Error("cannot create CloseableURLClassLoader", t);
}
}
/**
* Close any jar files that may have been opened by the class loader.
* Reflection is used to access the jar files in the URLClassLoader's
* internal data structures.
* @throws java.io.IOException if the jar files cannot be found for any
* reson, or if closing the jar file itself causes an IOException.
*/
@Override
public void close() throws IOException {
try {
for (Object l: getLoaders()) {
if (l.getClass().getName().equals("sun.misc.URLClassPath$JarLoader")) {
Field jarField = l.getClass().getDeclaredField("jar");
JarFile jar = (JarFile) getField(l, jarField);
if (jar != null) {
//System.err.println("CloseableURLClassLoader: closing " + jar);
jar.close();
}
}
}
} catch (Throwable t) {
IOException e = new IOException("cannot close class loader");
e.initCause(t);
throw e;
}
}
private ArrayList getLoaders()
throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException
{
Field ucpField = URLClassLoader.class.getDeclaredField("ucp");
Object urlClassPath = getField(this, ucpField);
if (urlClassPath == null)
throw new AssertionError("urlClassPath not set in URLClassLoader");
Field loadersField = urlClassPath.getClass().getDeclaredField("loaders");
return (ArrayList) getField(urlClassPath, loadersField);
}
private Object getField(Object o, Field f)
throws IllegalArgumentException, IllegalAccessException {
boolean prev = f.isAccessible();
try {
f.setAccessible(true);
return f.get(o);
} finally {
f.setAccessible(prev);
}
}
}