Loader.java Source code

Introduction

Here is the source code for Loader.java

Source

// 
// Copyright 2004-2005 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// 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.
// 

import java.net.URL;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

/* ------------------------------------------------------------ */
/** ClassLoader Helper.
 * This helper class allows classes to be loaded either from the
 * Thread's ContextClassLoader, the classloader of the derived class
 * or the system ClassLoader.
 *
 * <B>Usage:</B><PRE>
 * public class MyClass {
 *     void myMethod() {
 *          ...
 *          Class c=Loader.loadClass(this.getClass(),classname);
 *          ...
 *     }
 * </PRE>          
 * @author Greg Wilkins (gregw)
 */
public class Loader {
    /* ------------------------------------------------------------ */
    public static URL getResource(Class loadClass, String name, boolean checkParents)
            throws ClassNotFoundException {
        URL url = null;
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        while (url == null && loader != null) {
            url = loader.getResource(name);
            loader = (url == null && checkParents) ? loader.getParent() : null;
        }

        loader = loadClass == null ? null : loadClass.getClassLoader();
        while (url == null && loader != null) {
            url = loader.getResource(name);
            loader = (url == null && checkParents) ? loader.getParent() : null;
        }

        if (url == null) {
            url = ClassLoader.getSystemResource(name);
        }

        return url;
    }

    /* ------------------------------------------------------------ */
    public static Class loadClass(Class loadClass, String name) throws ClassNotFoundException {
        return loadClass(loadClass, name, false);
    }

    /* ------------------------------------------------------------ */
    /** Load a class.
     * 
     * @param loadClass
     * @param name
     * @param checkParents If true, try loading directly from parent classloaders.
     * @return Class
     * @throws ClassNotFoundException
     */
    public static Class loadClass(Class loadClass, String name, boolean checkParents)
            throws ClassNotFoundException {
        ClassNotFoundException ex = null;
        Class c = null;
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        while (c == null && loader != null) {
            try {
                c = loader.loadClass(name);
            } catch (ClassNotFoundException e) {
                if (ex == null)
                    ex = e;
            }
            loader = (c == null && checkParents) ? loader.getParent() : null;
        }

        loader = loadClass == null ? null : loadClass.getClassLoader();
        while (c == null && loader != null) {
            try {
                c = loader.loadClass(name);
            } catch (ClassNotFoundException e) {
                if (ex == null)
                    ex = e;
            }
            loader = (c == null && checkParents) ? loader.getParent() : null;
        }

        if (c == null) {
            try {
                c = Class.forName(name);
            } catch (ClassNotFoundException e) {
                if (ex == null)
                    ex = e;
            }
        }

        if (c != null)
            return c;
        throw ex;
    }

    public static ResourceBundle getResourceBundle(Class loadClass, String name, boolean checkParents,
            Locale locale) throws MissingResourceException {
        MissingResourceException ex = null;
        ResourceBundle bundle = null;
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        while (bundle == null && loader != null) {
            try {
                bundle = ResourceBundle.getBundle(name, locale, loader);
            } catch (MissingResourceException e) {
                if (ex == null)
                    ex = e;
            }
            loader = (bundle == null && checkParents) ? loader.getParent() : null;
        }

        loader = loadClass == null ? null : loadClass.getClassLoader();
        while (bundle == null && loader != null) {
            try {
                bundle = ResourceBundle.getBundle(name, locale, loader);
            } catch (MissingResourceException e) {
                if (ex == null)
                    ex = e;
            }
            loader = (bundle == null && checkParents) ? loader.getParent() : null;
        }

        if (bundle == null) {
            try {
                bundle = ResourceBundle.getBundle(name, locale);
            } catch (MissingResourceException e) {
                if (ex == null)
                    ex = e;
            }
        }

        if (bundle != null)
            return bundle;
        throw ex;
    }

}