Metacat

public class MetacatReplication extends HttpServlet implements Runnable

  private static MetaCatUtil util = new MetaCatUtil();

  private Vector fileLocks = new Vector();

  private Thread lockThread = null;

      else if(((String[])params.get("action"))[0].equals("getlock"))

      {

        handleGetLockRequest(out, params, response);

      }

      else if(((String[])params.get("action"))[0].equals("getdocumentinfo"))

      {

        handleGetDocumentInfoRequest(out, params, response);

      }

  /**

   * Grants or denies a lock to a requesting host.

   * The servlet parameters of interrest are:

   * docid: the docid of the file the lock is being requested for

   * currentdate: the timestamp of the document on the remote server

   * 

   */

  private void handleGetLockRequest(PrintWriter out, Hashtable params,

                                    HttpServletResponse response)

  {

    java.util.Date remoteDate = new java.util.Date();

    java.util.Date localDate = new java.util.Date();

    try

    {

      Connection conn = util.openDBConnection();

      String docid = ((String[])params.get("docid"))[0];

      String remoteDateStr = ((String[])params.get("updatedate"))[0];

      DocumentImpl requestDoc = new DocumentImpl(conn, docid);

      String localDateStr = requestDoc.getUpdateDate();

      SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");

      ParsePosition pos = new ParsePosition(0);

      remoteDate = formatter.parse(remoteDateStr, pos);

      localDate = formatter.parse(localDateStr, pos);

      if(remoteDate.compareTo(localDate) >= 0)

      {

        if(!fileLocks.contains(docid))

        { //grant the lock

          fileLocks.add(0, docid); //insert at the beginning of the queue Vector

          //send a message back to the the remote host authorizing the insert

          out.println("<lockgranted><docid>" +docid+ "</docid></lockgranted>");

          lockThread = new Thread(this);

          lockThread.setPriority(Thread.MIN_PRIORITY);

          lockThread.start();

        }

        else

        { //deny the lock

          out.println("<filelocked><docid>" + docid + "</docid></filelocked>");

        }

      }

      else

      {//deny the lock.

        out.println("<outdatedfile><docid>" + docid + "</docid></filelocked>");

      }

      conn.close();

    }

    catch(Exception e)

    {

      System.out.println("error requesting file lock: " + e.getMessage());

    }

  }

  /**

   * Sends all of the xml_documents information encoded in xml to a requestor

   */

  private void handleGetDocumentInfoRequest(PrintWriter out, Hashtable params, 

                                        HttpServletResponse response)

  {

    String docid = ((String[])(params.get("docid")))[0];

    StringBuffer sb = new StringBuffer();

    try

    {

      Connection conn = util.openDBConnection();

      DocumentImpl doc = new DocumentImpl(conn, docid);

      sb.append("<documentinfo><docid>").append(docid);

      sb.append("</docid><docname>").append(doc.getDocname());

      sb.append("</docname><doctype>").append(doc.getDoctype());

      sb.append("</doctype><doctitle>").append(doc.getDocTitle());

      sb.append("</doctitle><user_owner>").append(doc.getUserowner());

      sb.append("</user_owner><user_updated>").append(doc.getUserupdated());

      sb.append("</user_updated><public_access>").append(doc.getPublicaccess());

      sb.append("</public_access></documentinfo>");

      response.setContentType("text/xml");

      out.println(sb.toString());

      conn.close();

    }

    catch (Exception e)

    {

      System.out.println("error in metacatReplication.handlegetdocumentinforequest: " + 

      e.getMessage());

    }

  }

  /**

   * Sends a document to a remote host

   */

                                        HttpServletResponse response)

    sql.append("to_date('").append(dateString);

    sql.append("','YY-MM-DD HH24:MI:SS')");

    delsql.append("select docid, date_updated, server_location from ");

    delsql.append("xml_documents) and date_updated > to_date('");

  /**

   * This method is what is run when a seperate thread is broken off to handle

   * inserting a document from a remote replicated server.

   */

  public void run()

  {

    try

    {

      Thread.sleep(30000); //the lock will expire in 30 seconds

      fileLocks.remove(fileLocks.size() - 1);

      //the vector is treated as a FIFO queue.  If there are more than one lock

      //in the vector, the first one inserted will be removed.

    }

    catch(Exception e)

    {

      System.out.println("error in file lock thread: " + e.getMessage());

    }

  }

  /**

   * Returns the name of a server given a serverCode

   * @param serverCode the serverid of the server

   * @return the servername or null if the specified serverCode does not

   *         exist.

   */

  public static String getServer(int serverCode)

  {

    try

    {

      Connection conn = util.openDBConnection();

      PreparedStatement pstmt = conn.prepareStatement("select server from " +

                              "xml_replication where serverid = " + 

                              serverCode);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tablehasrows = rs.next();

      if(tablehasrows)

      {

        conn.close();

        return rs.getString(1);

      }

      conn.close();

    }

    catch(Exception e)

    {

      System.out.println("Error in MetacatReplication.getServer: " + 

                          e.getMessage());

    }

    return null;

      //return null if the server does not exist

  }