238 lines
9.0 KiB
Java
238 lines
9.0 KiB
Java
/* Engine -- generic getInstance method.
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Copyright (C) 2003 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.java.security;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.InvocationTargetException;
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import java.security.NoSuchAlgorithmException;
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import java.security.Provider;
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/**
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* Generic implementation of the getInstance methods in the various
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* engine classes in java.security.
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* <p>
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* These classes ({@link java.security.Signature} for example) can be
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* thought of as the "chrome, upholstery, and steering wheel", and the SPI
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* (service provider interface, e.g. {@link java.security.SignatureSpi})
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* classes can be thought of as the "engine" -- providing the actual
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* functionality of whatever cryptographic algorithm the instance
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* represents.
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*
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* @see Provider
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* @author Casey Marshall
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*/
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public final class Engine
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{
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// Constants.
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// ------------------------------------------------------------------------
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/** Prefix for aliases. */
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private static final String ALG_ALIAS = "Alg.Alias.";
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/** Maximum number of aliases to try. */
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private static final int MAX_ALIASES = 5;
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/** Argument list for no-argument constructors. */
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private static final Object[] NO_ARGS = new Object[0];
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// Constructor.
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// ------------------------------------------------------------------------
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/** This class cannot be instantiated. */
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private Engine() { }
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// Class method.
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// ------------------------------------------------------------------------
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/**
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* Get the implementation for <i>algorithm</i> for service
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* <i>service</i> from <i>provider</i>. The service is e.g.
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* "Signature", and the algorithm "DSA".
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*
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* @param service The service name.
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* @param algorithm The name of the algorithm to get.
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* @param provider The provider to get the implementation from.
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* @return The engine class for the specified algorithm; the object
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* returned is typically a subclass of the SPI class for that
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* service, but callers should check that this is so.
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* @throws NoSuchAlgorithmException If the implementation cannot be
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* found or cannot be instantiated.
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* @throws InvocationTargetException If the SPI class's constructor
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* throws an exception.
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* @throws IllegalArgumentException If any of the three arguments are null.
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*/
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public static Object getInstance(String service, String algorithm,
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Provider provider)
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throws InvocationTargetException, NoSuchAlgorithmException
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{
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return getInstance(service, algorithm, provider, NO_ARGS);
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}
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/**
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* Get the implementation for <i>algorithm</i> for service
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* <i>service</i> from <i>provider</i>, passing <i>initArgs</i> to the
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* SPI class's constructor (which cannot be null; pass a zero-length
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* array if the SPI takes no arguments). The service is e.g.
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* "Signature", and the algorithm "DSA".
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*
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* @param service The service name.
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* @param algorithm The name of the algorithm to get.
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* @param provider The provider to get the implementation from.
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* @param initArgs The arguments to pass to the SPI class's
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* constructor (cannot be null).
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* @return The engine class for the specified algorithm; the object
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* returned is typically a subclass of the SPI class for that
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* service, but callers should check that this is so.
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* @throws NoSuchAlgorithmException If the implementation cannot be
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* found or cannot be instantiated.
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* @throws InvocationTargetException If the SPI class's constructor
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* throws an exception.
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* @throws IllegalArgumentException If any of the four arguments are null.
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*/
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public static Object getInstance(String service, String algorithm,
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Provider provider, Object[] initArgs)
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throws InvocationTargetException, NoSuchAlgorithmException
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{
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if (service == null || algorithm == null
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|| provider == null || initArgs == null)
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throw new IllegalArgumentException();
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// If there is no property "service.algorithm"
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if (provider.getProperty(service + "." + algorithm) == null)
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{
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// Iterate through aliases, until we find the class name or resolve
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// too many aliases.
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String alias = null;
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int count = 0;
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while ((alias = provider.getProperty(
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ALG_ALIAS + service + "." + algorithm)) != null)
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{
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if (algorithm.equals(alias)) // Refers to itself!
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break;
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algorithm = alias;
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if (count++ > MAX_ALIASES)
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throw new NoSuchAlgorithmException("too many aliases");
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}
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if (provider.getProperty(service + "." + algorithm) == null)
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throw new NoSuchAlgorithmException(algorithm);
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}
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// Find and instantiate the implementation.
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Class clazz = null;
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ClassLoader loader = provider.getClass().getClassLoader();
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Constructor constructor = null;
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String error = algorithm;
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try
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{
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if (loader != null)
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clazz = loader.loadClass(provider.getProperty(service+"."+algorithm));
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else
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clazz = Class.forName(provider.getProperty(service+"."+algorithm));
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constructor = getCompatibleConstructor(clazz, initArgs);
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return constructor.newInstance(initArgs);
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}
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catch (ClassNotFoundException cnfe)
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{
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error = "class not found: " + algorithm;
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}
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catch (IllegalAccessException iae)
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{
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error = "illegal access: " + iae.getMessage();
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}
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catch (InstantiationException ie)
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{
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error = "instantiation exception: " + ie.getMessage();
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}
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catch (ExceptionInInitializerError eiie)
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{
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error = "exception in initializer: " + eiie.getMessage();
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}
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catch (SecurityException se)
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{
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error = "security exception: " + se.getMessage();
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}
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catch (NoSuchMethodException nsme)
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{
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error = "no appropriate constructor found";
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}
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throw new NoSuchAlgorithmException(error);
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}
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// Own methods.
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// ------------------------------------------------------------------------
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/**
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* Find a constructor in the given class that can take the specified
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* argument list, allowing any of which to be null.
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*
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* @param clazz The class from which to get the constructor.
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* @param initArgs The argument list to be passed to the constructor.
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* @return The constructor.
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* @throws NoSuchMethodException If no constructor of the given class
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* can take the specified argument array.
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*/
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private static Constructor getCompatibleConstructor(Class clazz,
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Object[] initArgs)
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throws NoSuchMethodException
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{
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Constructor[] c = clazz.getConstructors();
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outer:for (int i = 0; i < c.length; i++)
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{
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Class[] argTypes = c[i].getParameterTypes();
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if (argTypes.length != initArgs.length)
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continue;
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for (int j = 0; j < argTypes.length; j++)
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{
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if (initArgs[j] != null &&
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!argTypes[j].isAssignableFrom(initArgs[j].getClass()))
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continue outer;
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}
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// If we reach this point, we know this constructor (c[i]) has
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// the same number of parameters as the target parameter list,
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// and all our parameters are either (1) null, or (2) assignable
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// to the target parameter type.
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return c[i];
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}
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throw new NoSuchMethodException();
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}
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}
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