jakarta.ws.rs.sse.FactoryFinder Maven / Gradle / Ivy
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/*
* Copyright (c) 2010, 2019 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 jakarta.ws.rs.sse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Properties;
import java.util.ServiceLoader;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Factory finder utility class.
*
* @author Paul Sandoz
* @author Marc Hadley
* @author Marek Potociar
* @since 2.1
*/
final class FactoryFinder {
private static final Logger LOGGER = Logger.getLogger(FactoryFinder.class.getName());
private FactoryFinder() {
// prevents instantiation
}
private static ClassLoader getContextClassLoader() {
// For performance reasons, check if a security manager is installed. If not there is no need to use a
// privileged action.
if (System.getSecurityManager() == null) {
return Thread.currentThread().getContextClassLoader();
}
return AccessController.doPrivileged((PrivilegedAction) () -> {
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 {@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 {@code Class} for the given factory name and create its instance.
*
* 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 service service to be found.
* @param 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 Object find(final String factoryId, final Class service) throws ClassNotFoundException {
ClassLoader classLoader = getContextClassLoader();
// First try the TCCL
Object result = findFirstService(factoryId, classLoader, service);
if (result != null) {
return result;
}
// Next try the class loader from the FactoryFinder
result = findFirstService(factoryId, getClassLoader(), service);
if (result != null) {
return result;
}
// 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);
}
throw new ClassNotFoundException(
"Provider for " + factoryId + " cannot be found", null);
}
private static ClassLoader getClassLoader() {
if (System.getSecurityManager() == null) {
return FactoryFinder.class.getClassLoader();
}
return AccessController.doPrivileged((PrivilegedAction) FactoryFinder.class::getClassLoader);
}
private static T findFirstService(final String factoryId, final ClassLoader cl, final Class service) {
final PrivilegedAction action = () -> {
try {
final ServiceLoader loader = ServiceLoader.load(service, cl);
if (loader.iterator().hasNext()) {
return loader.iterator().next();
}
} catch (Exception e) {
LOGGER.log(Level.FINER, "Failed to load service " + factoryId + ".", e);
}
return null;
};
if (System.getSecurityManager() == null) {
return action.run();
}
return AccessController.doPrivileged(action);
}
}