javassist.LoaderClassPath Maven / Gradle / Ivy
/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. Alternatively, the contents of this file may be used under
* the terms of the GNU Lesser General Public License Version 2.1 or later,
* or the Apache License Version 2.0.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*/
package javassist;
import java.io.InputStream;
import java.net.URL;
import java.lang.ref.WeakReference;
/**
* A class search-path representing a class loader.
*
* It is used for obtaining a class file from the given
* class loader by getResourceAsStream().
* The LoaderClassPath refers to the class loader through
* WeakReference. If the class loader is garbage collected,
* the other search pathes are examined.
*
*
The given class loader must have both getResourceAsStream()
* and getResource().
*
*
Class files in a named module are private to that module.
* This method cannot obtain class files in named modules.
*
*
* @author Bill Burke
* @author Shigeru Chiba
*
* @see ClassPool#insertClassPath(ClassPath)
* @see ClassPool#appendClassPath(ClassPath)
* @see ClassClassPath
* @see ModuleClassPath
*/
public class LoaderClassPath implements ClassPath {
private WeakReference clref;
/**
* If true, this search path implicitly includes
* a {@code ModuleClassPath} as a fallback.
* For backward compatibility, this field is set to true
* if the JVM is Java 9 or later. It can be false in
* Java 9 but the behavior of {@code LoadClassPath} will
* be different from its behavior in Java 8 or older.
*
* This field must be false if the JVM is Java 8 or older.
*
* @since 3.21
*/
public static boolean fallbackOnModuleClassPath
= javassist.bytecode.ClassFile.MAJOR_VERSION >= javassist.bytecode.ClassFile.JAVA_9;
private static ModuleClassPath moduleClassPath = null;
private boolean doFallback;
/**
* Creates a search path representing a class loader.
*/
public LoaderClassPath(ClassLoader cl) {
this(cl, fallbackOnModuleClassPath);
}
LoaderClassPath(ClassLoader cl, boolean fallback) {
clref = new WeakReference(cl);
doFallback = fallback;
if (fallback)
synchronized (LoaderClassPath.class) {
if (moduleClassPath == null)
moduleClassPath = new ModuleClassPath();
}
}
public String toString() {
Object cl = null;
if (clref != null)
cl = clref.get();
return cl == null ? "" : cl.toString();
}
/**
* Obtains a class file from the class loader.
* This method calls getResourceAsStream(String)
* on the class loader.
*/
public InputStream openClassfile(String classname) throws NotFoundException {
String cname = classname.replace('.', '/') + ".class";
ClassLoader cl = (ClassLoader)clref.get();
if (cl == null)
return null; // not found
else {
InputStream is = cl.getResourceAsStream(cname);
if (is == null && doFallback)
return moduleClassPath.openClassfile(classname);
else
return is;
}
}
/**
* Obtains the URL of the specified class file.
* This method calls getResource(String)
* on the class loader.
*
* @return null if the class file could not be found.
*/
public URL find(String classname) {
String cname = classname.replace('.', '/') + ".class";
ClassLoader cl = (ClassLoader)clref.get();
if (cl == null)
return null; // not found
else {
URL url = cl.getResource(cname);
if (url == null && doFallback)
return moduleClassPath.find(classname);
else
return url;
}
}
/**
* Closes this class path.
*/
public void close() {
clref = null;
}
}