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The RichFaces core framework.
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/*
* JBoss, Home of Professional Open Source
* Copyright 2013, Red Hat, Inc. and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.richfaces.application;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.regex.Pattern;
import com.google.common.collect.Iterables;
/**
*
* This class loads services from files placed to the META-INF/services in classpath.
*
*
* @author [email protected]
*
*/
public final class ServiceLoader {
private static final String META_INF_SERVICES = "META-INF/services/";
private static final Pattern LEGAL_JAVA_NAME = Pattern.compile("^(([A-Za-z0-9_])+[\\.\\$])+[A-Z]([A-Za-z0-9_]*)$");
private ServiceLoader() {
}
/**
*
* Load and instantiate all service implementations.
*
*
* @param
* @param serviceClass
* @return
* @throws ServiceException
*/
public static Collection loadServices(Class serviceClass) throws ServiceException {
Collection> serviceClasses = loadServiceClasses(serviceClass);
List instances = new ArrayList();
for (Class implementationClass : serviceClasses) {
instances.add(createInstance(implementationClass));
}
return instances;
}
public static S loadService(Class serviceClass, Class defaultImplementation) {
Collection> serviceClasses = loadServiceClasses(serviceClass);
try {
return createInstance(Iterables.getLast(serviceClasses));
} catch (NoSuchElementException e) {
return createInstance(defaultImplementation);
}
}
public static S loadService(Class serviceClass) {
Collection> serviceClasses = loadServiceClasses(serviceClass);
try {
return createInstance(Iterables.getLast(serviceClasses));
} catch (NoSuchElementException e) {
return null;
}
}
private static S createInstance(Class implementationClass) {
try {
return implementationClass.newInstance();
} catch (InstantiationException e) {
throw new ServiceException("Cannot instantiate service class, does it have default constructor ?", e);
} catch (IllegalAccessException e) {
throw new ServiceException("Cannot instantiate service class, illegal access", e);
}
}
/**
*
* Load service implementation classes.
*
*
* @param
* @param serviceClass
* @return
* @throws ServiceException
*/
public static Collection> loadServiceClasses(Class serviceClass) throws ServiceException {
ClassLoader classLoader = getClassLoader(serviceClass);
Set names = new LinkedHashSet();
Enumeration resources;
try {
resources = classLoader.getResources(META_INF_SERVICES + serviceClass.getName());
while (resources.hasMoreElements()) {
names.addAll(parse(resources.nextElement()));
}
} catch (IOException e) {
throw new ServiceException("Error load service descriptions", e);
}
Set> instanceClasses = new LinkedHashSet>();
for (String className : names) {
instanceClasses.add(loadClass(serviceClass, classLoader, className));
}
return instanceClasses;
}
static Collection parse(URL url) throws ServiceException, IOException {
InputStream inputStream = null;
try {
URLConnection connection = url.openConnection();
try {
connection.setUseCaches(false);
} catch (IllegalArgumentException e) {
// Do nothing.
}
Set names = new HashSet();
inputStream = connection.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"));
String line;
while (null != (line = reader.readLine())) {
parseLine(line, names);
}
return names;
} finally {
if (null != inputStream) {
inputStream.close();
}
}
}
/**
*
* Parse a single line from service description. Skips empty lines and comments started with #
*
*
* @param line
* @param names
* @throws ServiceException
*/
static void parseLine(String line, Collection names) throws ServiceException {
String name;
int commentIndex = line.indexOf('#');
if (commentIndex >= 0) {
name = line.substring(0, commentIndex);
} else {
name = line;
}
name = name.trim();
if (name.length() > 0) {
if (LEGAL_JAVA_NAME.matcher(name).matches()) {
names.add(name);
} else {
throw new ServiceException("Invalid java class name [" + line + "]");
}
}
}
/**
*
* Get class loader
*
*
* @param
* @param serviceClass
* @return context class loader or loader with which service class has been loaded.
*/
private static ClassLoader getClassLoader(Class serviceClass) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (null == classLoader) {
classLoader = serviceClass.getClassLoader();
}
return classLoader;
}
private static Class loadClass(Class serviceClass, ClassLoader classLoader, String className)
throws ServiceException {
try {
Class implementationClass = classLoader.loadClass(className);
if (serviceClass.isAssignableFrom(implementationClass)) {
return implementationClass.asSubclass(serviceClass);
} else {
throw new ServiceException("Class " + className + " in not the instance of " + serviceClass.getName());
}
} catch (ClassNotFoundException e) {
throw new ServiceException("Class " + className + " not found", e);
}
}
}