Spring Framework example source code file (WebLogicClassLoader.java)

This example Spring Framework source code file (WebLogicClassLoader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

class, classloader, classloader, could, exception, illegalstateexception, illegalstateexception, method, object, object, reflection, string, weblogic, weblogic, weblogicclassloader

The Spring Framework WebLogicClassLoader.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 * 
 * Licensed 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.springframework.instrument.classloading.weblogic;

import java.lang.instrument.ClassFileTransformer;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import org.springframework.util.Assert;

/**
 * Reflective wrapper around a WebLogic 10 class loader. Used to
 * encapsulate the classloader-specific methods (discovered and
 * called through reflection) from the load-time weaver.
 * 
 * @author Costin Leau
 * @author Juergen Hoeller
 * @since 2.5
 */
class WebLogicClassLoader {

	private static final String GENERIC_CLASS_LOADER_NAME = "weblogic.utils.classloaders.GenericClassLoader";

	private static final String CLASS_PRE_PROCESSOR_NAME = "weblogic.utils.classloaders.ClassPreProcessor";


	private final ClassLoader internalClassLoader;

	private final Class wlPreProcessorClass;

	private final Method addPreProcessorMethod;

	private final Method getClassFinderMethod;

	private final Method getParentMethod;

	private final Constructor wlGenericClassLoaderConstructor;


	public WebLogicClassLoader(ClassLoader classLoader) {
		Class wlGenericClassLoaderClass = null;
		try {
			wlGenericClassLoaderClass = classLoader.loadClass(GENERIC_CLASS_LOADER_NAME);
			this.wlPreProcessorClass = classLoader.loadClass(CLASS_PRE_PROCESSOR_NAME);
			this.addPreProcessorMethod = classLoader.getClass().getMethod(
					"addInstanceClassPreProcessor", this.wlPreProcessorClass);
			this.getClassFinderMethod = classLoader.getClass().getMethod("getClassFinder");
			this.getParentMethod = classLoader.getClass().getMethod("getParent");
			this.wlGenericClassLoaderConstructor = wlGenericClassLoaderClass.getConstructor(
					this.getClassFinderMethod.getReturnType(), ClassLoader.class);
		}
		catch (Exception ex) {
			throw new IllegalStateException(
					"Could not initialize WebLogic ClassLoader because WebLogic 10 API classes are not available", ex);
		}
		Assert.isInstanceOf(wlGenericClassLoaderClass, classLoader,
				"ClassLoader must be instance of [" + wlGenericClassLoaderClass.getName() + "]");
		this.internalClassLoader = classLoader;
	}


	public void addTransformer(ClassFileTransformer transformer) {
		Assert.notNull(transformer, "ClassFileTransformer must not be null");
		try {
			InvocationHandler adapter = new WebLogicClassPreProcessorAdapter(transformer, this.internalClassLoader);
			Object adapterInstance = Proxy.newProxyInstance(this.wlPreProcessorClass.getClassLoader(),
					new Class[] {this.wlPreProcessorClass}, adapter);
			this.addPreProcessorMethod.invoke(this.internalClassLoader, adapterInstance);
		}
		catch (InvocationTargetException ex) {
			throw new IllegalStateException("WebLogic addInstanceClassPreProcessor method threw exception", ex.getCause());
		}
		catch (Exception ex) {
			throw new IllegalStateException("Could not invoke WebLogic addInstanceClassPreProcessor method", ex);
		}
	}

	public ClassLoader getInternalClassLoader() {
		return this.internalClassLoader;
	}

	public ClassLoader getThrowawayClassLoader() {
		try {
			Object classFinder = this.getClassFinderMethod.invoke(this.internalClassLoader);
			Object parent = this.getParentMethod.invoke(this.internalClassLoader);
			// arguments for 'clone'-like method
			return (ClassLoader) this.wlGenericClassLoaderConstructor.newInstance(classFinder, parent);
		}
		catch (InvocationTargetException ex) {
			throw new IllegalStateException("WebLogic GenericClassLoader constructor failed", ex.getCause());
		}
		catch (Exception ex) {
			throw new IllegalStateException("Could not construct WebLogic GenericClassLoader", ex);
		}
	}

}