geronimo-jaxrpc_1.1_spec/src/main/java/javax/xml/rpc/FactoryFinder.java

/*
 * 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 javax.xml.rpc;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Properties;

import org.apache.geronimo.osgi.locator.ProviderLocator;

/**
 * This code is designed to implement the pluggability
 * feature and is designed to both compile and run on JDK version 1.1 and
 * later.  The code also runs both as part of an unbundled jar file and
 * when bundled as part of the JDK.
 *
 * This class is duplicated for each subpackage so keep it in sync.
 * It is package private and therefore is not exposed as part of the JAXRPC
 * API.
 *
 * @version $Rev$ $Date$
 */
class FactoryFinder {
    /** Set to true for debugging. */
    private static final boolean debug = false;

    private static void debugPrintln(String msg) {
        if (debug) {
            System.err.println("JAXRPC: " + msg);
        }
    }

    /**
     * Figure out which ClassLoader to use.  For JDK 1.2 and later use
     * the context ClassLoader.
     *
     * @return the <code>ClassLoader</code>
     * @throws ConfigurationError   if this class is unable to work with the
     *              host JDK
     */
    private static ClassLoader findClassLoader()
        throws ConfigurationError
    {
        Method m = null;

        try {
            m = Thread.class.getMethod("getContextClassLoader", null);
        } catch (NoSuchMethodException e) {
            // Assume that we are running JDK 1.1, use the current ClassLoader
            debugPrintln("assuming JDK 1.1");
            return FactoryFinder.class.getClassLoader();
        }

        try {
            return (ClassLoader) m.invoke(Thread.currentThread(), null);
        } catch (IllegalAccessException e) {
            // assert(false)
            throw new ConfigurationError("Unexpected IllegalAccessException",
                                         e);
        } catch (InvocationTargetException e) {
            // assert(e.getTargetException() instanceof SecurityException)
            throw new ConfigurationError("Unexpected InvocationTargetException",
                                         e);
        }
    }

    /**
     * Create an instance of a class using the specified
     * <code>ClassLoader</code>, or if that fails from the
     * <code>ClassLoader</code> that loaded this class.
     *
     * @param className     the name of the class to instantiate
     * @param classLoader   a <code>ClassLoader</code> to load the class from
     *
     * @return a new <code>Object</code> that is an instance of the class of
     *              the given name from the given class loader
     * @throws ConfigurationError   if the class could not be found or
     *              instantiated
     */
    private static Object newInstance(String className,
                                      ClassLoader classLoader)
        throws ConfigurationError
    {
        try {
            return ProviderLocator.loadClass(className, FactoryFinder.class, classLoader).newInstance();
        } catch (ClassNotFoundException x) {
            throw new ConfigurationError(
                "Provider " + className + " not found", x);
        } catch (Exception x) {
            throw new ConfigurationError(
                "Provider " + className + " could not be instantiated: " + x,
                x);
        }
    }

    /**
     * Finds the implementation Class object in the specified order.  Main
     * entry point.
     * @return Class object of factory, never null
     *
     * @param factoryId             Name of the factory to find, same as
     *                              a property name
     * @param fallbackClassName     Implementation class name, if nothing else
     *                              is found.  Use null to mean no fallback.
     *
     * @exception FactoryFinder.ConfigurationError
     *
     * Package private so this code can be shared.
     */
    static Object find(Class<?> factoryType, String fallbackClassName)
        throws ConfigurationError
    {
        String factoryId = factoryType.getName();

        debugPrintln("debug is on");

        // NOTE:  The spec does not identify the search order for this,
        // other than to note it can be overridden by the system property. The
        // STAX ordering is used here.

        ClassLoader classLoader = findClassLoader();

        // Use the system property first
        try {
            String systemProp =
                System.getProperty( factoryId );
            if( systemProp!=null) {
                debugPrintln("found system property " + systemProp);
                return newInstance(systemProp, classLoader);
            }
        } catch (SecurityException se) {
        }

        try {
            // try to read from $java.home/lib/jaxrpc.properties
            String factoryClassName =  ProviderLocator.lookupByJREPropertyFile("lib" + File.separator + "jaxrpc.properties", factoryId);
            if (factoryClassName != null) {
                debugPrintln("found java.home property " + factoryClassName);
                return newInstance(factoryClassName, classLoader);
            }
        } catch (Exception ex) {
            if( debug ) ex.printStackTrace();
        }


        try {
            // check the META-INF/services definitions, and return it if
            // we find something.
            Object service = ProviderLocator.getService(factoryId, FactoryFinder.class, classLoader);
            if (service != null) {
                return service;
            }
        } catch (Exception ex) {
            if( debug ) ex.printStackTrace();
        }

        if (fallbackClassName == null) {
            throw new ConfigurationError(
                "Provider for " + factoryId + " cannot be found", null);
        }

        debugPrintln("loaded from fallback value: " + fallbackClassName);
        return newInstance(fallbackClassName, classLoader);
    }

    static class ConfigurationError extends Error {
        // fixme: should this be refactored to use the jdk1.4 exception
        // wrapping?

        private Exception exception;

        /**
         * Construct a new instance with the specified detail string and
         * exception.
         *
         * @param msg   the Message for this error
         * @param x     an Exception that caused this failure, or null
         */
        ConfigurationError(String msg, Exception x) {
            super(msg);
            this.exception = x;
        }

        Exception getException() {
            return exception;
        }
    }
}