Source for gnu.java.security.sig.SignatureFactory

   1: /* SignatureFactory.java --
   2:    Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2 of the License, or (at
   9: your option) any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: USA
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version.  */
  37: 
  38: 
  39: package gnu.java.security.sig;
  40: 
  41: import gnu.java.security.Registry;
  42: import gnu.java.security.sig.dss.DSSSignature;
  43: import gnu.java.security.sig.rsa.RSASignatureFactory;
  44: 
  45: import java.util.Collections;
  46: import java.util.HashSet;
  47: import java.util.Set;
  48: 
  49: /**
  50:  * A Factory to instantiate signature-with-appendix handlers.
  51:  */
  52: public class SignatureFactory
  53: {
  54:   private static Set names;
  55: 
  56:   /** Trivial constructor to enforce Singleton pattern. */
  57:   private SignatureFactory()
  58:   {
  59:     super();
  60:   }
  61: 
  62:   /**
  63:    * Returns an instance of a signature-with-appendix scheme given its name.
  64:    *
  65:    * @param ssa the case-insensitive signature-with-appendix scheme name.
  66:    * @return an instance of the scheme, or <code>null</code> if none found.
  67:    */
  68:   public static final ISignature getInstance(String ssa)
  69:   {
  70:     if (ssa == null)
  71:       return null;
  72: 
  73:     ssa = ssa.trim();
  74:     ssa = ssa.toLowerCase();
  75:     ISignature result = null;
  76:     if (ssa.equalsIgnoreCase(Registry.DSA_SIG) || ssa.equals(Registry.DSS_SIG))
  77:       result = new DSSSignature();
  78:     else if (ssa.startsWith(Registry.RSA_SIG_PREFIX))
  79:       result = RSASignatureFactory.getInstance(ssa);
  80: 
  81:     return result;
  82:   }
  83: 
  84:   /**
  85:    * Returns a {@link Set} of signature-with-appendix scheme names supported by
  86:    * this <i>Factory</i>.
  87:    *
  88:    * @return a {@link Set} of signature-with-appendix scheme names (Strings).
  89:    */
  90:   public static synchronized final Set getNames()
  91:   {
  92:     if (names == null)
  93:       {
  94:         HashSet hs = new HashSet();
  95:         hs.add(Registry.DSS_SIG);
  96:         hs.addAll(RSASignatureFactory.getNames());
  97:         names = Collections.unmodifiableSet(hs);
  98:       }
  99:     return names;
 100:   }
 101: }