001    /* RMIClassLoader.java --
002       Copyright (c) 1996, 1997, 1998, 1999, 2002, 2003, 2004
003       Free Software Foundation, Inc.
004    
005    This file is part of GNU Classpath.
006    
007    GNU Classpath is free software; you can redistribute it and/or modify
008    it under the terms of the GNU General Public License as published by
009    the Free Software Foundation; either version 2, or (at your option)
010    any later version.
011    
012    GNU Classpath is distributed in the hope that it will be useful, but
013    WITHOUT ANY WARRANTY; without even the implied warranty of
014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015    General Public License for more details.
016    
017    You should have received a copy of the GNU General Public License
018    along with GNU Classpath; see the file COPYING.  If not, write to the
019    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
020    02110-1301 USA.
021    
022    Linking this library statically or dynamically with other modules is
023    making a combined work based on this library.  Thus, the terms and
024    conditions of the GNU General Public License cover the whole
025    combination.
026    
027    As a special exception, the copyright holders of this library give you
028    permission to link this library with independent modules to produce an
029    executable, regardless of the license terms of these independent
030    modules, and to copy and distribute the resulting executable under
031    terms of your choice, provided that you also meet, for each linked
032    independent module, the terms and conditions of the license of that
033    module.  An independent module is a module which is not derived from
034    or based on this library.  If you modify this library, you may extend
035    this exception to your version of the library, but you are not
036    obligated to do so.  If you do not wish to do so, delete this
037    exception statement from your version. */
038    
039    package java.rmi.server;
040    
041    import gnu.classpath.ServiceFactory;
042    import gnu.classpath.SystemProperties;
043    import gnu.java.rmi.server.RMIClassLoaderImpl;
044    
045    import java.net.MalformedURLException;
046    import java.net.URL;
047    import java.util.Iterator;
048    
049    /**
050     * This class provides a set of public static utility methods for supporting
051     * network-based class loading in RMI. These methods are called by RMI's
052     * internal marshal streams to implement the dynamic class loading of types for
053     * RMI parameters and return values.
054     * @since 1.1
055     */
056    public class RMIClassLoader
057    {
058      /**
059       * This class isn't intended to be instantiated.
060       */
061      private RMIClassLoader() {}
062    
063      /**
064       * @deprecated
065       */
066      public static Class<?> loadClass(String name)
067        throws MalformedURLException, ClassNotFoundException
068      {
069        return loadClass("", name);
070      }
071    
072      public static Class<?> loadClass(String codebase, String name)
073        throws MalformedURLException, ClassNotFoundException
074      {
075        RMIClassLoaderSpi spi = getProviderInstance();
076        if (spi == null)
077          spi = getDefaultProviderInstance(); 
078        return spi.loadClass(codebase, name, null);
079      }
080    
081      public static Class<?> loadClass(String codebase, String name,
082                                       ClassLoader defaultLoader)
083        throws MalformedURLException, ClassNotFoundException
084      {
085        RMIClassLoaderSpi spi = getProviderInstance();
086        if (spi == null)
087          spi = getDefaultProviderInstance(); 
088        return spi.loadClass(codebase, name, defaultLoader);
089      }
090    
091      public static Class<?> loadProxyClass (String codeBase, String[] interfaces,
092                                             ClassLoader defaultLoader)
093        throws MalformedURLException, ClassNotFoundException
094      {
095        RMIClassLoaderSpi spi = getProviderInstance();
096        if (spi == null)
097          spi = getDefaultProviderInstance();
098        return spi.loadProxyClass(codeBase, interfaces, defaultLoader);
099      }
100    
101      /**
102       * Loads a class from <code>codeBase</code>.
103       *
104       * This method delegates to
105       * {@link RMIClassLoaderSpi#loadClass(String, String, ClassLoader)} and
106       * passes <code>codeBase.toString()</code> as first argument,
107       * <code>name</code> as second argument and <code>null</code> as third
108       * argument.
109       *
110       * @param codeBase the code base from which to load the class
111       * @param name the name of the class
112       *
113       * @return the loaded class
114       *
115       * @throws MalformedURLException if the URL is not well formed
116       * @throws ClassNotFoundException if the requested class cannot be found
117       */
118      public static Class<?> loadClass(URL codeBase, String name)
119        throws MalformedURLException, ClassNotFoundException
120      {
121        RMIClassLoaderSpi spi = getProviderInstance();
122        if (spi == null)
123          spi = getDefaultProviderInstance(); 
124        return spi.loadClass(codeBase.toString(), name, null);
125      }
126    
127      /**
128       * Gets a classloader for the given codebase and with the current
129       * context classloader as parent.
130       * 
131       * @param codebase
132       * 
133       * @return a classloader for the given codebase
134       * 
135       * @throws MalformedURLException if the codebase contains a malformed URL
136       */
137      public static ClassLoader getClassLoader(String codebase) 
138        throws MalformedURLException
139      {
140        RMIClassLoaderSpi spi = getProviderInstance();
141        if (spi == null)
142          spi = getDefaultProviderInstance(); 
143        return spi.getClassLoader(codebase);
144      }
145     
146      /**
147       * Returns a string representation of the network location where a remote
148       * endpoint can get the class-definition of the given class.
149       *
150       * @param cl
151       *
152       * @return a space seperated list of URLs where the class-definition
153       * of cl may be found
154       */
155      public static String getClassAnnotation(Class<?> cl)
156      {
157        RMIClassLoaderSpi spi = getProviderInstance();
158        if (spi == null)
159          spi = getDefaultProviderInstance(); 
160        return spi.getClassAnnotation(cl);
161      }
162    
163      /**
164       * @deprecated
165       */
166      public static Object getSecurityContext (ClassLoader loader)
167      {
168        throw new Error ("Not implemented");
169      }
170    
171      /**
172       * Returns the default service provider for <code>RMIClassLoader</code>.
173       *
174       * @return the default provider for <code>RMIClassLoader</code>
175       */
176      public static RMIClassLoaderSpi getDefaultProviderInstance()
177      {
178        return RMIClassLoaderImpl.getInstance();
179      }
180    
181      /**
182       * Chooses, instantiates and returns a service provider.
183       *
184       * @return a service provider
185       */
186      private static RMIClassLoaderSpi getProviderInstance()
187      {
188        // If the user asked for the default, return it.  We do a special
189        // check here because our standard service lookup function does not
190        // handle this -- nor should it.
191        String prop = SystemProperties.getProperty("java.rmi.server.RMIClassLoaderSpi");
192        if ("default".equals(prop))
193          return null;
194        Iterator it = ServiceFactory.lookupProviders(RMIClassLoaderSpi.class,
195                                                     null);
196        if (it == null || ! it.hasNext())
197          return null;
198        // FIXME: the spec says we ought to throw an Error of some kind if
199        // the specified provider is not suitable for some reason.  However
200        // our service factory simply logs the problem and moves on to the next
201        // provider in this situation.
202        return (RMIClassLoaderSpi) it.next();
203      }
204    }