MagicObjectInputStream


1   package org.jgroups.util;
2   
3   import org.apache.commons.logging.Log;
4   import org.apache.commons.logging.LogFactory;
5   import org.jgroups.ChannelException;
6   import org.jgroups.conf.ClassConfigurator;
7   
8   import java.io.IOException  ;
9   import java.io.InputStream  ;
10  import java.io.ObjectStreamClass  ;
11  
12  /**
13   * Uses magic numbers for class descriptors
14   * @author Bela Ban
15   * @version $Id: MagicObjectInputStream.java,v 1.4 2004/10/04 20:47:57 belaban Exp $
16   */
17  public class MagicObjectInputStream extends ContextObjectInputStream {
18      static ClassConfigurator conf=null;
19      static final Log log=LogFactory.getLog(MagicObjectInputStream.class);
20  
21  
22      public MagicObjectInputStream(InputStream   is) throws IOException   {
23          super(is);
24          if(conf == null) {
25              try {
26                  conf=ClassConfigurator.getInstance(false);
27              }
28              catch(ChannelException e) {
29                  log.error("ClassConfigurator could not be instantiated", e);
30              }
31          }
32      }
33  
34  
35      protected ObjectStreamClass   readClassDescriptor() throws IOException  , ClassNotFoundException   {
36          ObjectStreamClass   retval;
37          int magic_num=super.readInt();
38  
39          if(conf == null || magic_num == -1) {
40              return super.readClassDescriptor();
41          }
42  
43          retval=conf.getObjectStreamClassFromMagicNumber(magic_num);
44          if(retval == null)
45              throw new ClassNotFoundException  ("failed fetching class descriptor for magic number " + magic_num);
46          //if(log.isTraceEnabled())
47              //log.trace("reading descriptor (from " + magic_num + "): " + retval.getName());
48          return retval;
49      }
50  }
51  
52
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