/*
 * 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.
 */
/*
 * $Id: ObjectFactory.java 468637 2006-10-28 06:51:02Z minchau $
 */

package org.apache.xalan.extensions;

/**
 * This class is duplicated for each JAXP subpackage so keep it in sync.
 * It is package private and therefore is not exposed as part of the JAXP
 * API.
 * <p>
 * This code is designed to implement the JAXP 1.1 spec pluggability
 * feature and is designed to run on JDK version 1.1 and
 * later, and to compile on JDK 1.2 and onward.  
 * The code also runs both as part of an unbundled jar file and
 * when bundled as part of the JDK.
 * <p>
 * This class was moved from the <code>javax.xml.parsers.ObjectFactory</code>
 * class and modified to be used as a general utility for creating objects 
 * dynamically.
 *
 * @version $Id: ObjectFactory.java 468637 2006-10-28 06:51:02Z minchau $
 */
class ObjectFactory {

    /**
     * Figure out which ClassLoader to use.  For JDK 1.2 and later use
     * the context ClassLoader.
     */
    static ClassLoader findClassLoader()
        throws ConfigurationError
    {
        // BEGIN android-changed
        //     the context class loader is always sufficient
        return Thread.currentThread().getContextClassLoader();
        // END android-changed
    } // findClassLoader():ClassLoader

    /**
     * Find a Class using the specified ClassLoader
     */ 
    static Class findProviderClass(String className, ClassLoader cl,
                                           boolean doFallback)
        throws ClassNotFoundException, ConfigurationError
    {   
        //throw security exception if the calling thread is not allowed to access the
        //class. Restrict the access to the package classes as specified in java.security policy.
        SecurityManager security = System.getSecurityManager();
        try{
                if (security != null){
                    final int lastDot = className.lastIndexOf(".");
                    String packageName = className;
                    if (lastDot != -1) packageName = className.substring(0, lastDot);
                    security.checkPackageAccess(packageName);
                 }   
        }catch(SecurityException e){
            throw e;
        }
        
        Class providerClass;
        if (cl == null) {
            // XXX Use the bootstrap ClassLoader.  There is no way to
            // load a class using the bootstrap ClassLoader that works
            // in both JDK 1.1 and Java 2.  However, this should still
            // work b/c the following should be true:
            //
            // (cl == null) iff current ClassLoader == null
            //
            // Thus Class.forName(String) will use the current
            // ClassLoader which will be the bootstrap ClassLoader.
            providerClass = Class.forName(className);
        } else {
            try {
                providerClass = cl.loadClass(className);
            } catch (ClassNotFoundException x) {
                if (doFallback) {
                    // Fall back to current classloader
                    ClassLoader current = ObjectFactory.class.getClassLoader();
                    if (current == null) {
                        providerClass = Class.forName(className);
                    } else if (cl != current) {
                        cl = current;
                        providerClass = cl.loadClass(className);
                    } else {
                        throw x;
                    }
                } else {
                    throw x;
                }
            }
        }

        return providerClass;
    }

    //
    // Classes
    //

    /**
     * A configuration error.
     */
    static class ConfigurationError 
        extends Error {
                static final long serialVersionUID = 8564305128443551853L;
        //
        // Data
        //

        /** Exception. */
        private Exception exception;

        //
        // Constructors
        //

        /**
         * Construct a new instance with the specified detail string and
         * exception.
         */
        ConfigurationError(String msg, Exception x) {
            super(msg);
            this.exception = x;
        } // <init>(String,Exception)

        //
        // Public methods
        //

        /** Returns the exception associated to this error. */
        Exception getException() {
            return exception;
        } // getException():Exception

    } // class ConfigurationError

} // class ObjectFactory