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ActiveMQ example source code file (FactoryFinder.java)

This example ActiveMQ source code file (FactoryFinder.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 - ActiveMQ tags/keywords

bufferedinputstream, class, class, classnotfoundexception, classnotfoundexception, illegalaccessexception, instantiationexception, io, ioexception, ioexception, object, objectfactory, objectfactory, properties, string, threading, threads, util

The ActiveMQ FactoryFinder.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.activemq.util;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 
 */
public class FactoryFinder {

    /**
     * The strategy that the FactoryFinder uses to find load and instantiate Objects
     * can be changed out by calling the
     * {@link org.apache.activemq.util.FactoryFinder#setObjectFactory(org.apache.activemq.util.FactoryFinder.ObjectFactory)}
     * method with a custom implementation of ObjectFactory.
     *
     * The default ObjectFactory is typically changed out when running in a specialized container
     * environment where service discovery needs to be done via the container system.  For example,
     * in an OSGi scenario.
     */
    public interface ObjectFactory {
        /**
         * @param path the full service path 
         * @return
         */
        public Object create(String path) throws IllegalAccessException, InstantiationException, IOException, ClassNotFoundException;

    }

    /**
     * The default implementation of Object factory which works well in standalone applications.
     */
    protected static class StandaloneObjectFactory implements ObjectFactory {
        final ConcurrentHashMap<String, Class> classMap = new ConcurrentHashMap();

        public Object create(final String path) throws InstantiationException, IllegalAccessException, ClassNotFoundException, IOException {
            Class clazz = classMap.get(path);
            if (clazz == null) {
                clazz = loadClass(loadProperties(path));
                classMap.put(path, clazz);
            }
            return clazz.newInstance();
        }

        static public Class loadClass(Properties properties) throws ClassNotFoundException, IOException {

            String className = properties.getProperty("class");
            if (className == null) {
                throw new IOException("Expected property is missing: class");
            }
            Class clazz = null;
            ClassLoader loader = Thread.currentThread().getContextClassLoader();
            if (loader != null) {
                try {
                    clazz = loader.loadClass(className);
                } catch (ClassNotFoundException e) {
                    // ignore
                }
            }
            if (clazz == null) {
                clazz = FactoryFinder.class.getClassLoader().loadClass(className);
            }

            return clazz;
        }

        static public Properties loadProperties(String uri) throws IOException {
            // lets try the thread context class loader first
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            if (classLoader == null) {
                classLoader = StandaloneObjectFactory.class.getClassLoader();
            }
            InputStream in = classLoader.getResourceAsStream(uri);
            if (in == null) {
                in = FactoryFinder.class.getClassLoader().getResourceAsStream(uri);
                if (in == null) {
                    throw new IOException("Could not find factory class for resource: " + uri);
                }
            }

            // lets load the file
            BufferedInputStream reader = null;
            try {
                reader = new BufferedInputStream(in);
                Properties properties = new Properties();
                properties.load(reader);
                return properties;
            } finally {
                try {
                    reader.close();
                } catch (Exception e) {
                }
            }
        }
    }

    // ================================================================
    // Class methods and properties
    // ================================================================
    private static ObjectFactory objectFactory = new StandaloneObjectFactory();

    public static ObjectFactory getObjectFactory() {
        return objectFactory;
    }

    public static void setObjectFactory(ObjectFactory objectFactory) {
        FactoryFinder.objectFactory = objectFactory;
    }

    // ================================================================
    // Instance methods and properties
    // ================================================================
    private final String path;

    public FactoryFinder(String path) {
        this.path = path;
    }

    /**
     * Creates a new instance of the given key
     *
     * @param key is the key to add to the path to find a text file containing
     *                the factory name
     * @return a newly created instance
     */
    public Object newInstance(String key) throws IllegalAccessException, InstantiationException, IOException, ClassNotFoundException {
        return objectFactory.create(path+key);
    }

    
}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ FactoryFinder.java source code file:

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