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Diffstat (limited to 'libjava/java/security/Engine.java')
| -rw-r--r-- | libjava/java/security/Engine.java | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/libjava/java/security/Engine.java b/libjava/java/security/Engine.java new file mode 100644 index 0000000..88ff536 --- /dev/null +++ b/libjava/java/security/Engine.java @@ -0,0 +1,152 @@ +/* Engine -- generic getInstance method. + Copyright (C) 2003 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA +02111-1307 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package java.security; + +/** + * Generic implementation of the getInstance methods in the various + * engine classes in java.security. + * <p> + * These classes ({@link java.security.Signature} for example) can be + * thought of as the "chrome, upholstery, and steering wheel", and the SPI + * (service provider interface, e.g. {@link java.security.SignatureSpi}) + * classes can be thought of as the "engine" -- providing the actual + * functionality of whatever cryptographic algorithm the instance + * represents. + * + * @see Provider + * @author Casey Marshall + */ +final class Engine +{ + + // Constants. + // ------------------------------------------------------------------------ + + /** Prefix for aliases. */ + private static final String ALG_ALIAS = "Alg.Alias."; + + /** Maximum number of aliases to try. */ + private static final int MAX_ALIASES = 5; + + // Constructor. + // ------------------------------------------------------------------------ + + /** This class cannot be instantiated. */ + private Engine() { } + + // Class method. + // ------------------------------------------------------------------------ + + /** + * Get the implementation for <i>algorithm</i> for service + * <i>service</i> from <i>provider</i>. The service is e.g. + * "Signature", and the algorithm "DSA". + * + * @param service The service name. + * @param algorithm The name of the algorithm to get. + * @param provider The provider to get the implementation from. + * @return The engine class for the specified algorithm; the object + * returned is typically a subclass of the SPI class for that + * service, but callers should check that this is so. + * @throws NoSuchAlgorithmException If the implementation cannot be + * found or cannot be instantiated. + * @throws IllegalArgumentException If any of the three arguments are null. + */ + static Object + getInstance(String service, String algorithm, Provider provider) + throws NoSuchAlgorithmException + { + if (service == null || algorithm == null || provider == null) + throw new IllegalArgumentException(); + + // If there is no property "service.algorithm" + if (provider.getProperty(service + "." + algorithm) == null) + { + // Iterate through aliases, until we find the class name or resolve + // too many aliases. + String alias = null; + int count = 0; + while ((alias = provider.getProperty( + ALG_ALIAS + service + "." + algorithm)) != null) + { + if (algorithm.equals(alias)) // Refers to itself! + break; + algorithm = alias; + if (count++ > MAX_ALIASES) + throw new NoSuchAlgorithmException("too many aliases"); + } + if (provider.getProperty(service + "." + algorithm) == null) + throw new NoSuchAlgorithmException(algorithm); + } + + // Find and instantiate the implementation. + Class clazz = null; + ClassLoader loader = provider.getClass().getClassLoader(); + String error = algorithm; + try + { + if (loader != null) + clazz = loader.loadClass(provider.getProperty(service+"."+algorithm)); + else + clazz = Class.forName(provider.getProperty(service+"."+algorithm)); + return clazz.newInstance(); + } + catch (ClassNotFoundException cnfe) + { + error = "class not found: " + algorithm; + } + catch (IllegalAccessException iae) + { + error = "illegal access: " + iae.getMessage(); + } + catch (InstantiationException ie) + { + error = "instantiation exception: " + ie.getMessage(); + } + catch (ExceptionInInitializerError eiie) + { + error = "exception in initializer: " + eiie.getMessage(); + } + catch (SecurityException se) + { + error = "security exception: " + se.getMessage(); + } + + throw new NoSuchAlgorithmException(error); + } +} |