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Commons Beanutils example source code file (ClassReloader.java)
The Commons Beanutils ClassReloader.java source code/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.beanutils.converters; import java.io.InputStream; import java.io.ByteArrayOutputStream; import java.io.FileNotFoundException; import java.io.IOException; /** * A special classloader useful for testing j2ee-like scenarios. * * <p>In some tests we want to be able to emulate "container" frameworks, * where code runs in a hierarchy of classloaders, and certain classes may * be loaded by various classloaders in the hierarchy.</p> * * <p>Normally this is done by having certain jars or class-file-directories * in the classpath of some classloaders but not others. This is quite * difficult difficult to integrate with the build process for the unit * tests though; compiling certain classes and having the output go into * places that is not in the default classpath for the unit tests would be * a major pain.</p> * * <p>So this class takes a sneaky alternative approach: it can grab any class * already loaded by a parent classloader and <i>reload that class via this * classloader. The effect is exactly as if a class (or jar file) had been * present in the classpath for a container's "shared" classloader <i>and * been present in the component-specific classpath too, without any messing * about with the way unit test code is compiled or executed. */ public class ClassReloader extends ClassLoader { public ClassReloader(ClassLoader parent) { super(parent); } /** * Given a class already in the classpath of a parent classloader, * reload that class via this classloader. */ public Class reload(Class clazz) throws FileNotFoundException, IOException { String className = clazz.getName(); String classFile = className.replace('.', '/') + ".class"; InputStream classStream = getParent().getResourceAsStream(classFile); if (classStream == null) { throw new FileNotFoundException(classFile); } byte[] buf = new byte[1024]; ByteArrayOutputStream baos = new ByteArrayOutputStream(); for(;;) { int bytesRead = classStream.read(buf); if (bytesRead == -1) break; baos.write(buf, 0, bytesRead); } classStream.close(); byte[] classData = baos.toByteArray(); // now we have the raw class data, let's turn it into a class Class newClass = defineClass(className, classData, 0, classData.length); resolveClass(newClass); return newClass; } } Other Commons Beanutils examples (source code examples)Here is a short list of links related to this Commons Beanutils ClassReloader.java source code file: |
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