org.apache.activemq.artemis.utils.FactoryFinder Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* 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.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.
*
* 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 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 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);
}
return clazz.newInstance();
}
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);
}
}