org.kuali.rice.core.api.util.ClassLoaderUtils.java Source code

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Here is the source code for org.kuali.rice.core.api.util.ClassLoaderUtils.java

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/**
 * Copyright 2005-2014 The Kuali Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
 *
 * 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.kuali.rice.core.api.util;

import org.apache.commons.lang.ClassUtils;
import org.apache.commons.lang.StringUtils;
import org.kuali.rice.core.api.exception.RiceRuntimeException;
import org.kuali.rice.core.api.util.reflect.TargetedInvocationHandler;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.util.Iterator;
import java.util.List;

/**
 * Provides common utility methods for dealing with Classloaders.
 *
 * @author Kuali Rice Team (rice.collab@kuali.org)
 */
public final class ClassLoaderUtils {

    private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(ClassLoaderUtils.class);

    private ClassLoaderUtils() {
        throw new UnsupportedOperationException("do not call");
    }

    /**
     * Returns the default class loader within the current context.  If there is a context classloader
     * it is returned, otherwise the classloader which loaded the ClassLoaderUtil Class is returned.
     *
     * @return the appropriate default classloader which is guaranteed to be non-null
     */
    public static ClassLoader getDefaultClassLoader() {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            classLoader = ClassLoaderUtils.class.getClassLoader();
        }
        return classLoader;
    }

    /**
     * Checks if the given object is an instance of the given class, unwrapping any proxies if
     * necessary to get to the underlying object.
     */
    public static boolean isInstanceOf(Object object, Class<?> instanceClass) {
        if (object == null) {
            return false;
        }
        if (instanceClass.isInstance(object)) {
            return true;
        }
        return isInstanceOf(unwrapFromProxyOnce(object), instanceClass);
    }

    public static Object unwrapFromProxy(Object proxy) {
        Object unwrapped = unwrapFromProxyOnce(proxy);
        if (unwrapped == null) {
            return proxy;
        }
        return unwrapFromProxy(unwrapped);
    }

    /**
     * Unwraps the underlying object from the given proxy (which may itself be a proxy).  If the
     * given object is not a valid proxy, then null is returned.
     */
    private static Object unwrapFromProxyOnce(Object proxy) {
        if (proxy != null && Proxy.isProxyClass(proxy.getClass())) {
            InvocationHandler invocationHandler = Proxy.getInvocationHandler(proxy);
            if (invocationHandler instanceof TargetedInvocationHandler) {
                return ((TargetedInvocationHandler) invocationHandler).getTarget();
            }
        }
        return null;
    }

    /**
     * Checks if the given Class is visible to the given ClassLoader.
     */
    public static boolean isClassVisible(ClassLoader classLoader, Class<?> classToCheck) {
        try {
            Class<?> classFound = classLoader.loadClass(classToCheck.getName());
            return classFound.equals(classToCheck);
        } catch (ClassNotFoundException e) {
            return false;
        }
    }

    /**
     * Determines the interfaces which need to be proxied and are visible to the given proxy ClassLoader.
     */
    public static Class[] getInterfacesToProxy(Object object, ClassLoader proxyClassLoader,
            String[] packageNamesToFilter) {
        List interfaces = ClassUtils.getAllInterfaces(object.getClass());
        outer: for (Iterator iterator = interfaces.iterator(); iterator.hasNext();) {
            Class objectInterface = (Class) iterator.next();
            // check package name filters
            if (packageNamesToFilter != null) {
                for (String packageNames : packageNamesToFilter) {
                    if (objectInterface.getName().startsWith(packageNames)) {
                        iterator.remove();
                        continue outer;
                    }
                }
            }
            // check that the interface is visible from the given classloader
            if (proxyClassLoader != null) {
                if (!ClassLoaderUtils.isClassVisible(proxyClassLoader, objectInterface)) {
                    if (LOG.isDebugEnabled()) {
                        LOG.debug("The interface " + objectInterface
                                + " was not visible from the proxy ClassLoader when attempting to proxy: "
                                + object);
                    }
                    iterator.remove();
                    continue outer;
                }
            }
        }
        Class[] interfaceArray = new Class[interfaces.size()];
        return (Class[]) interfaces.toArray(interfaceArray);
    }

    // TODO why not make this so that it throws ClassNoteFoundException and doesn't return null?
    // this is more standard behavior...
    public static Class<?> getClass(String className) {
        if (StringUtils.isEmpty(className)) {
            return null;
        }
        try {
            return ClassUtils.getClass(getDefaultClassLoader(), className);
        } catch (ClassNotFoundException e) {
            throw new RiceRuntimeException(e);
        }
    }

    public static <T> Class<? extends T> getClass(String className, Class<T> type) throws ClassNotFoundException {
        Class<?> theClass = ClassUtils.getClass(getDefaultClassLoader(), className);
        return theClass.asSubclass(type);
    }

}