001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.geronimo.kernel;
018
019 import java.io.BufferedReader;
020 import java.io.IOException;
021 import java.io.InputStream;
022 import java.io.InputStreamReader;
023
024 import org.apache.geronimo.kernel.basic.BasicKernelFactory;
025
026 /**
027 * @version $Rev: 549825 $ $Date: 2007-06-22 10:17:31 -0400 (Fri, 22 Jun 2007) $
028 */
029 public abstract class KernelFactory {
030 public static final String KERNEL_FACTORY_KEY = KernelFactory.class.getName();
031
032 public static KernelFactory newInstance() {
033 ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
034 if (classLoader == null) {
035 classLoader = KernelFactory.class.getClassLoader();
036 }
037
038 // System property
039 try {
040 String kernelFactoryName = System.getProperty(KERNEL_FACTORY_KEY);
041 if (kernelFactoryName != null) {
042 return createKernelFactory(kernelFactoryName, classLoader);
043 }
044 } catch (SecurityException se) {
045 }
046
047 // Jar Service Specification - http://java.sun.com/j2se/1.3/docs/guide/jar/jar.html
048 String serviceId = "META-INF/services/" + KERNEL_FACTORY_KEY;
049 InputStream inputStream = null;
050 try {
051 inputStream = classLoader.getResourceAsStream(serviceId);
052 if (inputStream != null) {
053 BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
054 String kernelFactoryName = reader.readLine();
055 reader.close();
056
057 if (kernelFactoryName != null && kernelFactoryName.length() > 0) {
058 return createKernelFactory(kernelFactoryName, classLoader);
059 }
060 }
061 } catch (Exception ignored) {
062 } finally {
063 if (inputStream != null) {
064 try {
065 inputStream.close();
066 } catch (IOException ignored) {
067 }
068 inputStream = null;
069 }
070 }
071
072 // Default is the basic kernel
073 return new BasicKernelFactory();
074 }
075
076 private static KernelFactory createKernelFactory(String className, ClassLoader classLoader) {
077 try {
078 return (KernelFactory) classLoader.loadClass(className).newInstance();
079 } catch (ClassCastException e) {
080 throw new KernelFactoryError("Kernel factory class does not implement KernelFactory: " + className, e);
081 } catch (ClassNotFoundException e) {
082 throw new KernelFactoryError("Kernel factory class not found: " + className, e);
083 } catch (Exception e) {
084 throw new KernelFactoryError("Unable to instantiate kernel factory class: " + className, e);
085 }
086 }
087
088 public abstract Kernel createKernel(String kernelName);
089 }