DynamicUpdater.java :  » Chat » jYMSG » ymsg » support » Java Open Source

package ymsg.support;

import java.io.*;
import java.net.*;
import java.util.jar.*;

// !!!EXPERIMENTAL!!!
// (Look, but don't trust!)

// *********************************************************************
// This code enables classes to be dynamically loaded and stored for
// future use.  It was mainly created to allow for automatic updates for
// the challenge/response code (which Yahoo repeatedly changes).
//
// Typical usage would be to attempt these three steps:
//  1) Try logging in with standard code.
//  2) Check localUpdateAvailable(), and if true try logging in with
//    newInstance().
//  3) Check remoteUpdateAvailable(), and if true call performUpdate()
//    and then try logging in with newInstance().
//  4) Give up!
//
// To create an update file:
//   1) Write the code according to the required Java interface.
//  2) Package all necessary classes into a Jar with required name
//     (for example "ymsgx_cr.jar").
//  3) Add a manifest with the following:
//    - jYMSG-X-Main : the class which implements the interface
//    - jYMSG-X-Version : integer version number
//  4) Create property file using Jar name plus ".properties" (eg.
//    "ymsgx_cr.jar.properties" which contains :
//    - jYMSG-X-Version : integer version number (same a manifest)
//  5) Make both files available on a web server.
//  6) Set the clients "ymsg.dynamic.baseURL" to the base URL of where
//    these two files are.
// *********************************************************************
public class DynamicUpdater
{  private final static String REMOTE_PROP = "ymsg.dynamic.baseURL";
  private final static String CR_FILE = "ymsgx_cr.jar";

  private URL versionURL,remoteURL,localURL;
  private File localFile;


  // -----------------------------------------------------------------
  // CONSTRUCTOR (private, use static)
  // -----------------------------------------------------------------
/*  private DynamicUpdater(String name)
  {  String remotePath = System.getProperty(REMOTE_PROP);
    String localPath = "./";  // FIX
    try
    {  remoteURL = new URL(remotePath,name);
      versionURL = new URL(remotePath,name+".properties");
      localFile = new File(localPath+name);
      localURL = new URL(localFile.toURL());
    }catch(MalformedURLException e) { e.printStackTrace(); }
  }

  public DynamicUpdater createChallengeResponseDynamicUpdater()
  {  return new DynamicUpdater(CR_FILE);
  }



  // -----------------------------------------------------------------
  // Loads an instance of the extension class
  // -----------------------------------------------------------------
  public Object newInstance()
  throws ClassNotFoundException, InstantiationException, IllegalAccessException, IOException
  {  // -----Is there a local update?
    if(!localUpdateAvailable())
      throw new ClassNotFoundException("No jYMSG update available");
    // -----Get the name of the class we need to construct
    JarFile jf = new JarFile(localFile);
    Attributes attrs = jf.getManifest().getMainAttributes();
    String className=attrs.getValue("jYMSG-X-Main");
    jf.close();
    // -----Get the class
    URL[] u = new URL[1];  u[0]=localURL;
    Loader l = new Loader(u);
    Class cls = findClass(className);
    return cls.newInstance();
  }

  private class Loader extends URLClassLoader
  {  private Loader(URL[] u) { super(u); }
  }

  // -----------------------------------------------------------------
  // Loads
  // -----------------------------------------------------------------
  public void performUpdate() throws IOException
  {  byte[] buffer = new byte[10*1024];

    File f = new File(localFile);
    FileOutputStream op = new FileOutputStream(f);
    InputStream ip = new remoteURL.openStream();
    int sz=ip.read(buffer);
    while(sz>0)
    {  op.write(buffer,0,sz);
      sz=ip.read(buffer);
    }
    dis.close();  dos.close();
  }

  // -----------------------------------------------------------------
  // Returns true if a local update has been downloaded
  // -----------------------------------------------------------------
  public boolean localUpdateAvailable()
  {  File f = new File(localFile);
    return f.exists();
  }

  // -----------------------------------------------------------------
  // Returns true if there is a remote update available and it is of
  // a higher version number than the current version.
  // -----------------------------------------------------------------
  public boolean remoteUpdateAvailable()
  {  int v1,v2;
    // -----Remote version number
    try
    {  Properties remoteProps = new Properties();
      InputStream in = versionURL.openStream();
      remoteProps.load(in);  in.close();
      v1=Integer.parseInt(
        remoteProps.getProperty("jYMSG-X-Version") );
    }catch(Exception e) { v1=0; }
    // -----Local version number
    try
    {  JarFile jf = new JarFile(localFile);
      Attributes attrs = jf.getManifest().getMainAttributes();
      int v2=Integer.parseInt(
        attrs.getValue("jYMSG-X-Version") );
      jf.close();
    }catch(Exception e) { v2=0; }
    // -----All done?  Return if update is available
    return (v2>v1);
  }
*/
}