jarclassloader.java

Java 3D Desktop Environment旨在使用Java 3D来创建一个3D桌面环境。功能包括：分布式的应用程序

package org.j3de.server;     

import java.io.InputStream; 
import java.io.IOException;  
import java.io.File;  
import java.net.MalformedURLException;    
import java.net.URL;                    
import java.security.CodeSource;
import java.security.PermissionCollection;
import java.security.SecureClassLoader;    
import java.util.jar.JarFile;
import java.util.zip.ZipEntry; 
import java.util.Enumeration;
import java.util.List;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Vector;

import org.j3de.exception.ExceptionHandler;

public class JarClassLoader extends SecureClassLoader {  
  private static JarClassLoader classLoader;
  
  private List   jarFiles;
  private Set    jarFileNames;
  
  private Map    codeSources;
  private Map    permissions;
      
  private JarClassLoader() { 
    this.jarFiles     = new Vector();     
    this.jarFileNames = new HashSet();  
    this.codeSources  = new HashMap();
    this.permissions  = new HashMap();
  }                                
  
  public Class findClass(String classname) throws ClassNotFoundException {
    byte[] b = null;
    JarFile jarfile = null;
    
    for (int i=0; i<jarFiles.size(); i++) {
      jarfile = (JarFile)jarFiles.get(i);      
      try {    
        b = loadClassFromJarFile(jarfile, classname);   
        break;
      } catch (ClassNotFoundException e) { 
      }      
    }
                   
    if (b == null) {
      ClassNotFoundException e = new ClassNotFoundException("Class " + classname + " not found !"); 
      ExceptionHandler.handleException(e);
      throw e;
    }
    
    return defineClass(classname, b, 0, b.length, (CodeSource)codeSources.get(jarfile));
  }                    
  
  private byte[] loadClassFromJarFile(JarFile jarfile, String classname) throws ClassNotFoundException {    
    try {    
      ZipEntry entry = jarfile.getEntry(classname.replace('.', '/') + ".class");    
      
      if (entry == null)  
        throw new ClassNotFoundException("Class " + classname + " not found in " + jarfile.getName());
        
      InputStream in = jarfile.getInputStream(entry); 
      int readBytes = 0;
      int size     =  (int)entry.getSize();
      int chunk;
      byte[] data = new byte[size];  
      while (readBytes < size) {
        chunk = in.read(data, readBytes, size - readBytes);      
        
        if (chunk == -1)
          break;
          
        readBytes += chunk;
      }         
      
      return data;    
    } catch (ClassFormatError e) { 
      throw new ClassNotFoundException("Damaged class in jarfile : " + jarfile.getName() + " : " + classname); 
    } catch (IOException e) {
      throw new ClassNotFoundException("IOException while loading class : " + jarfile.getName() + " : " + classname + 
                                       " " + e.getMessage()); 
    }   
    
  }
  
  private String getPropertyValue(String property) { 
    if (property.equals("/"))
      return File.separator;
    else
      return "";
  }                
  
  private String expandProperties(String path) {
    int pos, endPos;
    
    while ((pos = path.indexOf("${")) > 0) {
      String prefix = path.substring(0, pos); 
      path = path.substring(pos + 2);
      pos  = path.indexOf("}");
      String propertyName = path.substring(0, pos);
      path = prefix + getPropertyValue(propertyName) + path.substring(pos + 1);  
    }                                                                          
    
    return path;
  }                                                                            
  
  public void addJarFile(String jarFileName, PermissionCollection permissionCollection) {   
    try {                
      jarFileName = expandProperties(jarFileName);
      
      if (!jarFileNames.contains(jarFileName)) {
        jarFileNames.add(jarFileName);   
        JarFile file = new JarFile(jarFileName);                                        
        jarFiles.add(file);                                                             
        CodeSource cs = new CodeSource(new URL("file://" + jarFileName), null);
        codeSources.put(file, cs);
        permissions.put(cs, permissionCollection);
      }
    } catch (IOException e) {
      ExceptionHandler.handleException(e);
    }
  }
  
  public static JarClassLoader getClassLoader() {
    if (classLoader == null)
      classLoader = new JarClassLoader();
      
    return classLoader;
  }       
  
  protected PermissionCollection getPermissions(CodeSource codesource) {     
    return (PermissionCollection)permissions.get(codesource);
  }
}