jakarta.mail.util.FactoryFinder Maven / Gradle / Ivy
/*
* Copyright (c) 2021 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.mail.util;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.ServiceLoader;
class FactoryFinder {
/**
* Finds the implementation {@code Class} object for the given
* factory type.
* The arguments supplied must be used in order
* This method is package private so that this code can be shared.
*
* @return the {@code Class} object of the specified message factory
*
* @param factoryClass factory abstract class or interface to be found
* @exception RuntimeException if there is an error
*/
static T find(Class factoryClass) throws RuntimeException {
String factoryId = factoryClass.getName();
// Use the system property first
String className = fromSystemProperty(factoryId);
if (className != null) {
T result = newInstance(className);
if (result != null) {
return result;
}
}
// standard services: java.util.ServiceLoader
T factory = factoryFromServiceLoader(factoryClass);
if (factory != null) {
return factory;
}
// handling Glassfish/OSGi (platform specific default)
if (isOsgi()) {
T result = lookupUsingOSGiServiceLoader(factoryId);
if (result != null) {
return result;
}
}
throw new IllegalStateException("Not provider of " + factoryClass.getName() + " was found");
}
@SuppressWarnings({"unchecked"})
private static T newInstance(String className) throws RuntimeException {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
checkPackageAccess(className);
Class clazz = null;
try {
if (classLoader == null) {
clazz = (Class) Class.forName(className);
} else {
clazz = (Class) classLoader.loadClass(className);
}
return clazz.getConstructor().newInstance();
} catch (ReflectiveOperationException e) {
throw new IllegalArgumentException("Cannot instance " + className, e);
}
}
private static String fromSystemProperty(String factoryId) {
String systemProp = getSystemProperty(factoryId);
return systemProp;
}
private static String getSystemProperty(final String property) {
String value = AccessController.doPrivileged(new PrivilegedAction() {
@Override
public String run() {
return System.getProperty(property);
}
});
return value;
}
private static final String OSGI_SERVICE_LOADER_CLASS_NAME = "org.glassfish.hk2.osgiresourcelocator.ServiceLoader";
private static boolean isOsgi() {
try {
Class.forName(OSGI_SERVICE_LOADER_CLASS_NAME);
return true;
} catch (ClassNotFoundException ignored) {
}
return false;
}
@SuppressWarnings({"unchecked"})
private static T lookupUsingOSGiServiceLoader(String factoryId) {
try {
// Use reflection to avoid having any dependency on HK2 ServiceLoader class
Class serviceClass = Class.forName(factoryId);
Class[] args = new Class[]{serviceClass};
Class target = Class.forName(OSGI_SERVICE_LOADER_CLASS_NAME);
Method m = target.getMethod("lookupProviderInstances", Class.class);
Iterator iter = ((Iterable) m.invoke(null, (Object[]) args)).iterator();
return iter.hasNext() ? (T) iter.next() : null;
} catch (Exception ignored) {
// log and continue
return null;
}
}
private static T factoryFromServiceLoader(Class factory) {
try {
ServiceLoader sl = ServiceLoader.load(factory);
Iterator iter = sl.iterator();
if (iter.hasNext()) {
return iter.next();
} else {
return null;
}
} catch (Throwable t) {
// For example, ServiceConfigurationError can be thrown if the factory class is not declared with 'uses' in module-info
throw new IllegalStateException("Cannot load " + factory + " as ServiceLoader", t);
}
}
private static void checkPackageAccess(String className) {
// make sure that the current thread has an access to the package of the given name.
SecurityManager s = System.getSecurityManager();
if (s != null) {
int i = className.lastIndexOf('.');
if (i != -1) {
s.checkPackageAccess(className.substring(0, i));
}
}
}
}