Ant example source code file (LoaderUtils.java)

This example Ant source code file (LoaderUtils.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 - Ant tags/keywords

buildexception, buildexception, classloader, file, file, file_utils, fileutils, io, loaderutils, string, string, thread, thread

The LoaderUtils.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.tools.ant.util;

import java.io.File;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.launch.Locator;

// CheckStyle:HideUtilityClassConstructorCheck OFF - bc

/**
 * ClassLoader utility methods
 *
 */
public class LoaderUtils {

    /** Utilities used for file operations */
    private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();

    /**
     * Set the context classloader
     *
     * @param loader the ClassLoader to be used as the context class loader
     *      on the current thread.
     */
    public static void setContextClassLoader(ClassLoader loader) {
        Thread currentThread = Thread.currentThread();
        currentThread.setContextClassLoader(loader);
    }


    /**
     * JDK1.1 compatible access to set the context class loader.
     *
     * @return the ClassLoader instance being used as the context
     *      classloader on the current thread. Returns null on JDK 1.1
     */
    public static ClassLoader getContextClassLoader() {
        Thread currentThread = Thread.currentThread();
        return currentThread.getContextClassLoader();
    }

    /**
     * Indicates if the context class loader methods are available
     *
     * @return true if the get and set methods dealing with the context
     *      classloader are available.
     */
    public static boolean isContextLoaderAvailable() {
        return true;
    }

    /**
     * Normalize a source location
     *
     * @param source the source location to be normalized.
     *
     * @return the normalized source location.
     */
    private static File normalizeSource(File source) {
        if (source != null) {
            try {
                source = FILE_UTILS.normalize(source.getAbsolutePath());
            } catch (BuildException e) {
                // relative path
            }
        }

        return source;
    }

    /**
     * Find the directory or jar file the class has been loaded from.
     *
     * @param c the class whose location is required.
     * @return the file or jar with the class or null if we cannot
     *         determine the location.
     *
     * @since Ant 1.6
     */
    public static File getClassSource(Class c) {
        return normalizeSource(Locator.getClassSource(c));
    }

    /**
     * Find the directory or a give resource has been loaded from.
     *
     * @param c the classloader to be consulted for the source
     * @param resource the resource whose location is required.
     *
     * @return the file with the resource source or null if
     *         we cannot determine the location.
     *
     * @since Ant 1.6
     */
    public static File getResourceSource(ClassLoader c, String resource) {
        if (c == null) {
            c = LoaderUtils.class.getClassLoader();
        }
        return normalizeSource(Locator.getResourceSource(c, resource));
    }

    /**
     * Return the resource name of a class name.
     * @param className the name of the class to convert.
     * @return the corresponding resource name.
     * @since Ant 1.7.0.
     */
    public static String classNameToResource(String className) {
        return className.replace('.', '/') + ".class";
    }

    /**
     * Check if a classloader has a classname resource.
     * @param loader the classloader to look it.
     * @param className the name of the class to look for.
     * @return true if the classexists, false otherwise
     * @since Ant 1.7.0.
     */
    public static boolean classExists(ClassLoader loader, String className) {
        return loader.getResource(classNameToResource(className)) != null;
    }
}