/*
* Copyright (c) 2010, 2017 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package javax.ws.rs.ext;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.Properties;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.logging.Level;
import java.util.logging.Logger;
Factory finder utility class.
Author: Paul Sandoz, Marc Hadley, Marek Potociar Since: 1.0
/**
* Factory finder utility class.
*
* @author Paul Sandoz
* @author Marc Hadley
* @author Marek Potociar
* @since 1.0
*/
final class FactoryFinder {
private static final Logger LOGGER = Logger.getLogger(FactoryFinder.class.getName());
private FactoryFinder() {
// prevents instantiation
}
private static ClassLoader getContextClassLoader() {
return AccessController.doPrivileged((PrivilegedAction<ClassLoader>) () -> {
ClassLoader cl = null;
try {
cl = Thread.currentThread().getContextClassLoader();
} catch (SecurityException ex) {
LOGGER.log(
Level.WARNING,
"Unable to get context classloader instance.",
ex);
}
return cl;
});
}
Creates an instance of the specified class using the specified ClassLoader object. Params: - className – name of the class to be instantiated.
- classLoader – class loader to be used.
Throws: - ClassNotFoundException – if the given class could not be found
or could not be instantiated.
Returns: instance of the specified class.
/**
* Creates an instance of the specified class using the specified
* {@code ClassLoader} object.
*
* @param className name of the class to be instantiated.
* @param classLoader class loader to be used.
* @return instance of the specified class.
* @throws ClassNotFoundException if the given class could not be found
* or could not be instantiated.
*/
private static Object newInstance(final String className, final ClassLoader classLoader) throws ClassNotFoundException {
try {
Class<?> spiClass;
if (classLoader == null) {
spiClass = Class.forName(className);
} else {
try {
spiClass = Class.forName(className, false, classLoader);
} catch (ClassNotFoundException ex) {
LOGGER.log(
Level.FINE,
"Unable to load provider class " + className
+ " using custom classloader " + classLoader.getClass().getName()
+ " trying again with current classloader.",
ex);
spiClass = Class.forName(className);
}
}
return spiClass.getDeclaredConstructor().newInstance();
} catch (ClassNotFoundException x) {
throw x;
} catch (Exception x) {
throw new ClassNotFoundException("Provider " + className + " could not be instantiated: " + x, x);
}
}
Finds the implementation Class for the given factory name, or if that fails, finds the Class for the given fallback class name and create its instance. The arguments supplied MUST be used in order. If using the first argument is successful, the second one will not be used.
This method is package private so that this code can be shared.
Params: - factoryId – the name of the factory to find, which is
a system property.
- fallbackClassName – the implementation class name, which is to be used only if nothing else. is found;
null to indicate that there is no fallback class name. - service – service to be found.
Type parameters: - <T> – type of the service to be found.
Throws: - ClassNotFoundException – if the given class could not be found
or could not be instantiated.
Returns: the instance of the specified service; may not be null.
/**
* Finds the implementation {@code Class} for the given factory name,
* or if that fails, finds the {@code Class} for the given fallback
* class name and create its instance. The arguments supplied MUST be
* used in order. If using the first argument is successful, the second
* one will not be used.
* <p>
* This method is package private so that this code can be shared.
*
* @param factoryId the name of the factory to find, which is
* a system property.
* @param fallbackClassName the implementation class name, which is
* to be used only if nothing else.
* is found; {@code null} to indicate that
* there is no fallback class name.
* @param service service to be found.
* @param <T> type of the service to be found.
* @return the instance of the specified service; may not be {@code null}.
* @throws ClassNotFoundException if the given class could not be found
* or could not be instantiated.
*/
static <T> Object find(final String factoryId, final String fallbackClassName, Class<T> service) throws ClassNotFoundException {
ClassLoader classLoader = getContextClassLoader();
try {
Iterator<T> iterator = ServiceLoader.load(service, FactoryFinder.getContextClassLoader()).iterator();
if(iterator.hasNext()) {
return iterator.next();
}
} catch (Exception | ServiceConfigurationError ex) {
LOGGER.log(Level.FINER, "Failed to load service " + factoryId + ".", ex);
}
try {
Iterator<T> iterator = ServiceLoader.load(service, FactoryFinder.class.getClassLoader()).iterator();
if(iterator.hasNext()) {
return iterator.next();
}
} catch (Exception | ServiceConfigurationError ex) {
LOGGER.log(Level.FINER, "Failed to load service " + factoryId + ".", ex);
}
// try to read from $java.home/lib/jaxrs.properties
FileInputStream inputStream = null;
String configFile = null;
try {
String javah = System.getProperty("java.home");
configFile = javah + File.separator + "lib" + File.separator + "jaxrs.properties";
File f = new File(configFile);
if (f.exists()) {
Properties props = new Properties();
inputStream = new FileInputStream(f);
props.load(inputStream);
String factoryClassName = props.getProperty(factoryId);
return newInstance(factoryClassName, classLoader);
}
} catch (Exception ex) {
LOGGER.log(Level.FINER, "Failed to load service " + factoryId
+ " from $java.home/lib/jaxrs.properties", ex);
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException ex) {
LOGGER.log(Level.FINER, String.format("Error closing %s file.", configFile), ex);
}
}
}
// Use the system property
try {
String systemProp = System.getProperty(factoryId);
if (systemProp != null) {
return newInstance(systemProp, classLoader);
}
} catch (SecurityException se) {
LOGGER.log(Level.FINER, "Failed to load service " + factoryId
+ " from a system property", se);
}
if (fallbackClassName == null) {
throw new ClassNotFoundException(
"Provider for " + factoryId + " cannot be found", null);
}
return newInstance(fallbackClassName, classLoader);
}
}