/*
* Copyright 2007 Sun Microsystems, Inc.
*
* Licensed 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 com.rometools.propono.atom.server;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Properties;
/**
* Find {@link com.rometools.rome.propono.atom.server.AtomHandlerFactory} based on properties
* files.
*
* @deprecated Propono will be removed in Rome 2.
*/
@Deprecated
class FactoryFinder {
private static boolean debug = false;
private static Properties cacheProps = new Properties();
private static SecuritySupport ss = new SecuritySupport();
private static boolean firstTime = true;
private FactoryFinder() {
}
private static void dPrint(final String msg) {
if (debug) {
System.err.println("Propono: " + msg);
}
}
/**
* Create an instance of a class using the specified ClassLoader and optionally fall back to the
* current ClassLoader if not found.
*
* @param className Name of the concrete class corresponding to the service provider
*
* @param cl ClassLoader to use to load the class, null means to use the bootstrap ClassLoader
*
* @param doFallback true if the current ClassLoader should be tried as a fallback if the class
* is not found using cl
*/
private static Object newInstance(final String className, ClassLoader cl, final boolean doFallback) throws ConfigurationError {
try {
Class<?> providerClass;
if (cl == null) {
// If classloader is null Use the bootstrap ClassLoader.
// Thus Class.forName(String) will use the current
// ClassLoader which will be the bootstrap ClassLoader.
providerClass = Class.forName(className);
} else {
try {
providerClass = cl.loadClass(className);
} catch (final ClassNotFoundException x) {
if (doFallback) {
// Fall back to current classloader
cl = FactoryFinder.class.getClassLoader();
providerClass = cl.loadClass(className);
} else {
throw x;
}
}
}
final Object instance = providerClass.newInstance();
dPrint("created new instance of " + providerClass + " using ClassLoader: " + cl);
return instance;
} catch (final ClassNotFoundException x) {
throw new ConfigurationError("Provider " + className + " not found", x);
} catch (final Exception x) {
throw new ConfigurationError("Provider " + className + " could not be instantiated: " + x, x);
}
}
/**
* Finds the implementation Class object in the specified order. Main entry point.
*
* @return Class object of factory, never null
*
* @param factoryId Name of the factory to find, same as a property name
* @param fallbackClassName Implementation class name, if nothing else is found. Use null to
* mean no fallback.
*
* Package private so this code can be shared.
*/
static Object find(final String factoryId, final String fallbackClassName) throws ConfigurationError {
// Figure out which ClassLoader to use for loading the provider
// class. If there is a Context ClassLoader then use it.
ClassLoader classLoader = ss.getContextClassLoader();
if (classLoader == null) {
// if we have no Context ClassLoader
// so use the current ClassLoader
classLoader = FactoryFinder.class.getClassLoader();
}
dPrint("find factoryId =" + factoryId);
// Use the system property first
try {
final String systemProp = ss.getSystemProperty(factoryId);
if (systemProp != null) {
dPrint("found system property, value=" + systemProp);
return newInstance(systemProp, classLoader, true);
}
} catch (final SecurityException se) {
// if first option fails due to any reason we should try next option in the
// look up algorithm.
}
// try to read from /propono.properties
try {
final String configFile = "/propono.properties";
String factoryClassName = null;
if (firstTime) {
synchronized (cacheProps) {
if (firstTime) {
try {
final InputStream is = FactoryFinder.class.getResourceAsStream(configFile);
firstTime = false;
if (is != null) {
dPrint("Read properties file: " + configFile);
cacheProps.load(is);
}
} catch (final Exception intentionallyIgnored) {
}
}
}
}
factoryClassName = cacheProps.getProperty(factoryId);
if (factoryClassName != null) {
dPrint("found in $java.home/propono.properties, value=" + factoryClassName);
return newInstance(factoryClassName, classLoader, true);
}
} catch (final Exception ex) {
if (debug) {
ex.printStackTrace();
}
}
// Try Jar Service Provider Mechanism
final Object provider = findJarServiceProvider(factoryId);
if (provider != null) {
return provider;
}
if (fallbackClassName == null) {
throw new ConfigurationError("Provider for " + factoryId + " cannot be found", null);
}
dPrint("loaded from fallback value: " + fallbackClassName);
return newInstance(fallbackClassName, classLoader, true);
}
/*
* Try to find provider using Jar Service Provider Mechanism
* @return instance of provider class if found or null
*/
private static Object findJarServiceProvider(final String factoryId) throws ConfigurationError {
final String serviceId = "META-INF/services/" + factoryId;
InputStream is = null;
// First try the Context ClassLoader
ClassLoader cl = ss.getContextClassLoader();
if (cl != null) {
is = ss.getResourceAsStream(cl, serviceId);
// If no provider found then try the current ClassLoader
if (is == null) {
cl = FactoryFinder.class.getClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
}
} else {
// No Context ClassLoader, try the current
// ClassLoader
cl = FactoryFinder.class.getClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
}
if (is == null) {
// No provider found
return null;
}
dPrint("found jar resource=" + serviceId + " using ClassLoader: " + cl);
// Read the service provider name in UTF-8 as specified in
// the jar spec. Unfortunately this fails in Microsoft
// VJ++, which does not implement the UTF-8
// encoding. Theoretically, we should simply let it fail in
// that case, since the JVM is obviously broken if it
// doesn't support such a basic standard. But since there
// are still some users attempting to use VJ++ for
// development, we have dropped in a fallback which makes a
// second attempt using the platform's default encoding. In
// VJ++ this is apparently ASCII, which is a subset of
// UTF-8... and since the strings we'll be reading here are
// also primarily limited to the 7-bit ASCII range (at
// least, in English versions), this should work well
// enough to keep us on the air until we're ready to
// officially decommit from VJ++. [Edited comment from
// jkesselm]
BufferedReader rd;
try {
rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
} catch (final java.io.UnsupportedEncodingException e) {
rd = new BufferedReader(new InputStreamReader(is));
}
String factoryClassName = null;
try {
// XXX Does not handle all possible input as specified by the
// Jar Service Provider specification
factoryClassName = rd.readLine();
rd.close();
} catch (final IOException x) {
// No provider found
return null;
}
if (factoryClassName != null && !"".equals(factoryClassName)) {
dPrint("found in resource, value=" + factoryClassName);
// Note: here we do not want to fall back to the current
// ClassLoader because we want to avoid the case where the
// resource file was found using one ClassLoader and the
// provider class was instantiated using a different one.
return newInstance(factoryClassName, cl, false);
}
// No provider found
return null;
}
}