content: /*
   * 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.artemis.utils;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.lang.reflect.InvocationTargetException;
  import java.util.Properties;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  public class FactoryFinder {
  
     /**
      * The strategy that the FactoryFinder uses to find load and instantiate Objects can be changed out by calling the
      * setObjectFactory method with a custom implementation of ObjectFactory.
      * <p>
      * 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 {
  
        /**
         * Creates an {@code Object} based on the input
         *
         * @param path the full service path
         * @return {@code Object}
         * @throws IllegalAccessException illegal access
         * @throws InstantiationException on instantiation error
         * @throws IOException            On IO Error
         * @throws ClassNotFoundException On class not found error
         */
        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 ConcurrentMap<String, Class> classMap = new ConcurrentHashMap<>();
  
        @Override
        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);
           }
           try {
              return clazz.getDeclaredConstructor().newInstance();
           } catch (NoSuchMethodException | InvocationTargetException e) {
              throw new IOException(e);
           }
        }
  
        static 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;
        }
  
        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
           try (BufferedInputStream reader = new BufferedInputStream(in)) {
              Properties properties = new Properties();
              properties.load(reader);
              return properties;
           }
        }
     }
  
     // ================================================================
     // 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
      * @throws IllegalAccessException On illegal access
      * @throws InstantiationException On can not instantiate exception
      * @throws IOException            On IOException
      * @throws ClassNotFoundException When class not on class path
      */
     public Object newInstance(String key) throws IllegalAccessException, InstantiationException, IOException, ClassNotFoundException {
        return objectFactory.create(path + key);
     }
  }
  