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/**
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* '$RCSfile$'
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* Purpose: A Class that implements replication for metacat
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* Copyright: 2000 Regents of the University of California and the
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* National Center for Ecological Analysis and Synthesis
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* Authors: Chad Berkley
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* Release: @release@
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*
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* '$Author: berkley $'
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* '$Date: 2000-11-29 15:18:22 -0800 (Wed, 29 Nov 2000) $'
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* '$Revision: 573 $'
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*/
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package edu.ucsb.nceas.metacat;
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import java.util.*;
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import java.io.*;
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import java.sql.*;
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import java.net.*;
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import java.lang.*;
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import java.text.*;
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import javax.servlet.*;
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import javax.servlet.http.*;
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import oracle.xml.parser.v2.*;
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import org.xml.sax.*;
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public class MetacatReplication extends HttpServlet implements Runnable
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{
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private String deltaT;
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Timer replicationDaemon;
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private static MetaCatUtil util = new MetaCatUtil();
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private Vector fileLocks = new Vector();
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private Thread lockThread = null;
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/**
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* Initialize the servlet by creating appropriate database connections
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*/
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public void init(ServletConfig config) throws ServletException
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{
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//initialize db connections to handle any update requests
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MetaCatUtil util = new MetaCatUtil();
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deltaT = util.getOption("deltaT");
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//break off a thread to do the delta-T check
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replicationDaemon = new Timer(true);
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//replicationDaemon.scheduleAtFixedRate(new replicationHandler(), 0,
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// new Integer(deltaT).intValue() * 1000);
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//System.out.println("timer scheduled at: " + new Integer(deltaT).intValue()
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// + " seconds");
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}
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public void destroy()
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{
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replicationDaemon.cancel();
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System.out.println("Replication daemon cancelled.");
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}
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public void doGet (HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException
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{
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// Process the data and send back the response
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handleGetOrPost(request, response);
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}
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public void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException
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{
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// Process the data and send back the response
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handleGetOrPost(request, response);
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}
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private void handleGetOrPost(HttpServletRequest request,
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HttpServletResponse response)
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throws ServletException, IOException
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{
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System.out.println("in metacatreplication");
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PrintWriter out = response.getWriter();
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Hashtable params = new Hashtable();
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Enumeration paramlist = request.getParameterNames();
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while (paramlist.hasMoreElements())
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{
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String name = (String)paramlist.nextElement();
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String[] value = request.getParameterValues(name);
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params.put(name, value);
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}
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if(params.containsKey("action"))
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{
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if(((String[])params.get("action"))[0].equals("stop"))
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{ //stop the replication server
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replicationDaemon.cancel();
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out.println("Replication Handler Stopped");
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System.out.println("Replication Handler Stopped");
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}
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else if(((String[])params.get("action"))[0].equals("start"))
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{ //start the replication server
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int rate;
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if(params.containsKey("rate"))
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{
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rate = new Integer(
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new String(((String[])params.get("rate"))[0])).intValue();
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if(rate < 30)
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{
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out.println("Replication deltaT rate cannot be less than 30!");
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rate = 1000;
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}
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}
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else
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{
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rate = 1000;
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}
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out.println("New rate is: " + rate + " seconds.");
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replicationDaemon.cancel();
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replicationDaemon = new Timer(true);
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replicationDaemon.scheduleAtFixedRate(new ReplicationHandler(out), 0,
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rate * 1000);
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out.println("Replication Handler Started");
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System.out.println("Replication Handler Started");
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}
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else if(((String[])params.get("action"))[0].equals("forcereplicate"))
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{
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String server = ((String[])params.get("server"))[0];
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int serverCheckCode = 0;
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try
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{
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serverCheckCode = MetacatReplication.getServerCode(server);
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}
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catch(Exception e)
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{
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System.out.println("error in metacatReplication.handleUpdateRequest"+
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": could not get server code");
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}
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replicationDaemon.schedule(new ReplicationHandler(out, serverCheckCode),
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2000);
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}
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else if(((String[])params.get("action"))[0].equals("update"))
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{ //request an update list from the server
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if(params.contains("servercheckcode"))
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{
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System.out.println("metacatreplication: servercheckcode: " +
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((int[])params.get("servercheckcode"))[0]);
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handleUpdateRequest(out, params, response,
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((int[])params.get("servercheckcode"))[0]);
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}
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else
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{
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handleUpdateRequest(out, params, response);
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}
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}
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else if(((String[])params.get("action"))[0].equals("read"))
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{ //request a specific document from the server
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//note that this could be replaced by a call to metacatServlet
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//handleGetDocumentAction().
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handleGetDocumentRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("getlock"))
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{
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handleGetLockRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("getdocumentinfo"))
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{
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handleGetDocumentInfoRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("gettime"))
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{
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handleGetTimeRequest(out, params, response);
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}
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}
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}
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/**
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* Grants or denies a lock to a requesting host.
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* The servlet parameters of interrest are:
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* docid: the docid of the file the lock is being requested for
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* currentdate: the timestamp of the document on the remote server
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*
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*/
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private void handleGetLockRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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java.util.Date remoteDate = new java.util.Date();
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java.util.Date localDate = new java.util.Date();
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try
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{
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Connection conn = util.openDBConnection();
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String docid = ((String[])params.get("docid"))[0];
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String remoteDateStr = ((String[])params.get("updatedate"))[0];
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DocumentImpl requestDoc = new DocumentImpl(conn, docid);
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String localDateStr = requestDoc.getUpdateDate();
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SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");
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ParsePosition pos = new ParsePosition(0);
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remoteDate = formatter.parse(remoteDateStr, pos);
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pos = new ParsePosition(0);
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localDate = formatter.parse(localDateStr, pos);
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if(remoteDate.compareTo(localDate) >= 0)
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{
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if(!fileLocks.contains(docid))
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{ //grant the lock
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fileLocks.add(0, docid); //insert at the beginning of the queue Vector
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//send a message back to the the remote host authorizing the insert
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out.println("<lockgranted><docid>" +docid+ "</docid></lockgranted>");
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lockThread = new Thread(this);
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lockThread.setPriority(Thread.MIN_PRIORITY);
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lockThread.start();
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}
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else
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{ //deny the lock
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out.println("<filelocked><docid>" + docid + "</docid></filelocked>");
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}
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}
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else
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{//deny the lock.
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out.println("<outdatedfile><docid>" + docid + "</docid></filelocked>");
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}
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conn.close();
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}
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catch(Exception e)
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{
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System.out.println("error requesting file lock: " + e.getMessage());
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e.printStackTrace(System.out);
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}
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}
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/**
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* Sends all of the xml_documents information encoded in xml to a requestor
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*/
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private void handleGetDocumentInfoRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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String docid = ((String[])(params.get("docid")))[0];
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StringBuffer sb = new StringBuffer();
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try
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{
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Connection conn = util.openDBConnection();
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DocumentImpl doc = new DocumentImpl(conn, docid);
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sb.append("<documentinfo><docid>").append(docid);
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sb.append("</docid><docname>").append(doc.getDocname());
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sb.append("</docname><doctype>").append(doc.getDoctype());
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sb.append("</doctype><doctitle>").append(doc.getDocTitle());
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sb.append("</doctitle><user_owner>").append(doc.getUserowner());
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sb.append("</user_owner><user_updated>").append(doc.getUserupdated());
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sb.append("</user_updated><public_access>").append(doc.getPublicaccess());
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sb.append("</public_access></documentinfo>");
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response.setContentType("text/xml");
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out.println(sb.toString());
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conn.close();
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}
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catch (Exception e)
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{
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System.out.println("error in metacatReplication.handlegetdocumentinforequest: " +
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e.getMessage());
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}
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}
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/**
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* Sends a document to a remote host
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*/
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private void handleGetDocumentRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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try
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{
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String docid = ((String[])(params.get("docid")))[0];
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System.out.println("incoming get request for document: " +
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docid);
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Connection conn = util.openDBConnection();
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DocumentImpl di = new DocumentImpl(conn, docid);
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response.setContentType("text/xml");
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out.print(di.toString());
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conn.close();
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}
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catch(Exception e)
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{
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System.out.println("error getting document: " + e.getMessage());
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}
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}
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/**
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* Does default handling for update requests
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*/
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private void handleUpdateRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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handleUpdateRequest(out, params, response, 1);
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}
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/**
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* Initiates an update of all server in the xml_replication table.
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* the remote host sends an update date. The local host (this method)
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* queries the db for any document that was updated after the update date
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* and returns a list of those documents to the remote host. It also
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* sends back a list of the files that were locally deleted.
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* serverCheckCode allows the requestor to request documents from this
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* server that reside on a different server. Normally, this server
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* should only replicate files that it owns but in the case of updating
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* a file that does not belong to this server, it is needed. See
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* DocumentImpl.write().
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*/
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private void handleUpdateRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response,
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int serverCheckCode)
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{
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System.out.println("incoming update request for dt/time " +
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((String[])params.get("date"))[0] +
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" from external metacat");
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response.setContentType("text/xml");
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StringBuffer returnXML = new StringBuffer();
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returnXML.append("<?xml version=\"1.0\"?><replication>");
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StringBuffer sql = new StringBuffer();
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String updateStr = ((String[])params.get("date"))[0];
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updateStr = updateStr.replace('+', ' ');
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//pseudo algorithm:
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///////////////////////////////////////////////////////////////////////
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//get the date/time from the requestor, query the db for any documents
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//that have an update date later than the requested date and send
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//those docids back to the requestor. If there are no newer documents
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//then send back a null message.
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///////////////////////////////////////////////////////////////////////
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//Timestamp update = Timestamp.valueOf(updateStr);
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SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");
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java.util.Date update = new java.util.Date();
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ParsePosition pos = new ParsePosition(0);
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update = formatter.parse(updateStr, pos);
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String dateString = formatter.format(update);
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sql.append("select docid, date_updated, server_location from ");
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sql.append("xml_documents where date_updated > ");
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sql.append("to_date('").append(dateString);
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sql.append("','YY-MM-DD HH24:MI:SS')");
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//System.out.println("sql: " + sql.toString());
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//get any recently deleted documents
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StringBuffer delsql = new StringBuffer();
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delsql.append("select docid, date_updated, server_location from ");
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delsql.append("xml_revisions where docid not in (select docid from ");
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delsql.append("xml_documents) and date_updated > to_date('");
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delsql.append(dateString).append("','YY-MM-DD HH24:MI:SS')");
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try
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{
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Connection conn = util.openDBConnection();
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PreparedStatement pstmt = conn.prepareStatement(sql.toString());
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pstmt.execute();
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ResultSet rs = pstmt.getResultSet();
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boolean tablehasrows = rs.next();
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//if a '1' should not represent localhost, add code here to query
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//xml_replication for the proper serverid number
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returnXML.append("<server>").append(util.getOption("server"));
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returnXML.append(util.getOption("replicationpath"));
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returnXML.append("</server><updates>");
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while(tablehasrows)
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{
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String docid = rs.getString(1);
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String dateUpdated = rs.getString(2);
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int serverCode = rs.getInt(3);
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if(serverCode == serverCheckCode)
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{ //check that this document is from this server.
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//servers only replicate their own documents!
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returnXML.append("<updatedDocument><docid>").append(docid);
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returnXML.append("</docid><date_updated>").append(dateUpdated);
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returnXML.append("</date_updated></updatedDocument>");
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}
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tablehasrows = rs.next();
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}
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pstmt = conn.prepareStatement(delsql.toString());
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pstmt.execute();
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rs = pstmt.getResultSet();
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tablehasrows = rs.next();
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while(tablehasrows)
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{ //handle the deleted documents
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String docid = rs.getString(1);
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String dateUpdated = rs.getString(2);
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int serverCode = rs.getInt(3);
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if(serverCode == 1)
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{
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returnXML.append("<deletedDocument><docid>").append(docid);
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returnXML.append("</docid><date_updated>").append(dateUpdated);
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returnXML.append("</date_updated></deletedDocument>");
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}
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tablehasrows = rs.next();
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}
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393
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returnXML.append("</updates></replication>");
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conn.close();
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//System.out.println(returnXML.toString());
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out.print(returnXML.toString());
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}
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catch(Exception e)
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{
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System.out.println("Exception in metacatReplication: " + e.getMessage());
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}
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}
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404
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|
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/**
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* Sends the current system date to the remote server. Using this action
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* for replication gets rid of any problems with syncronizing clocks
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408
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* because a time specific to a document is always kept on its home server.
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409
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*/
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410
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private void handleGetTimeRequest(PrintWriter out, Hashtable params,
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411
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HttpServletResponse response)
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412
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{
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413
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SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");
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414
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java.util.Date localtime = new java.util.Date();
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String dateString = formatter.format(localtime);
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response.setContentType("text/xml");
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out.println("<timestamp>" + dateString + "</timestamp>");
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419
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}
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420
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421
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/**
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422
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* This method is what is run when a seperate thread is broken off to handle
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423
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* inserting a document from a remote replicated server.
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424
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*/
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425
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public void run()
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426
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{
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427
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try
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428
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{
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429
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System.out.println("thread started for docid: " +
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(String)fileLocks.elementAt(0));
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431
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Thread.sleep(30000); //the lock will expire in 30 seconds
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432
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System.out.println("thread for docid: " +
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433
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(String)fileLocks.elementAt(fileLocks.size() - 1) +
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434
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" exiting.");
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435
|
fileLocks.remove(fileLocks.size() - 1);
|
436
|
//fileLocks is treated as a FIFO queue. If there are more than one lock
|
437
|
//in the vector, the first one inserted will be removed.
|
438
|
}
|
439
|
catch(Exception e)
|
440
|
{
|
441
|
System.out.println("error in file lock thread: " + e.getMessage());
|
442
|
}
|
443
|
}
|
444
|
|
445
|
/**
|
446
|
* Returns the name of a server given a serverCode
|
447
|
* @param serverCode the serverid of the server
|
448
|
* @return the servername or null if the specified serverCode does not
|
449
|
* exist.
|
450
|
*/
|
451
|
public static String getServer(int serverCode)
|
452
|
{
|
453
|
//System.out.println("serverid: " + serverCode);
|
454
|
try
|
455
|
{
|
456
|
Connection conn = util.openDBConnection();
|
457
|
String sql = new String("select server from " +
|
458
|
"xml_replication where serverid = " +
|
459
|
serverCode);
|
460
|
PreparedStatement pstmt = conn.prepareStatement(sql);
|
461
|
//System.out.println("getserver sql: " + sql);
|
462
|
pstmt.execute();
|
463
|
ResultSet rs = pstmt.getResultSet();
|
464
|
boolean tablehasrows = rs.next();
|
465
|
if(tablehasrows)
|
466
|
{
|
467
|
//System.out.println("server: " + rs.getString(1));
|
468
|
return rs.getString(1);
|
469
|
}
|
470
|
conn.close();
|
471
|
}
|
472
|
catch(Exception e)
|
473
|
{
|
474
|
System.out.println("Error in MetacatReplication.getServer: " +
|
475
|
e.getMessage());
|
476
|
}
|
477
|
return null;
|
478
|
//return null if the server does not exist
|
479
|
}
|
480
|
|
481
|
/**
|
482
|
* Returns a server code given a server name
|
483
|
* @param server the name of the server
|
484
|
* @return integer > 0 representing the code of the server, 0 if the server
|
485
|
* does not exist.
|
486
|
*/
|
487
|
public static int getServerCode(String server) throws Exception
|
488
|
{
|
489
|
try
|
490
|
{
|
491
|
Connection conn = util.openDBConnection();
|
492
|
PreparedStatement pstmt = conn.prepareStatement("select serverid from " +
|
493
|
"xml_replication where server " +
|
494
|
"like '" + server + "'");
|
495
|
pstmt.execute();
|
496
|
ResultSet rs = pstmt.getResultSet();
|
497
|
boolean tablehasrows = rs.next();
|
498
|
int serverCode = 0;
|
499
|
if(tablehasrows)
|
500
|
{
|
501
|
return rs.getInt(1);
|
502
|
}
|
503
|
else
|
504
|
{
|
505
|
return 0;
|
506
|
}
|
507
|
}
|
508
|
catch(Exception e)
|
509
|
{
|
510
|
throw e;
|
511
|
}
|
512
|
}
|
513
|
|
514
|
/**
|
515
|
* This method returns the content of a url
|
516
|
* @param u the url to return the content from
|
517
|
* @return a string representing the content of the url
|
518
|
* @throws java.io.IOException
|
519
|
*/
|
520
|
public static String getURLContent(URL u) throws java.io.IOException
|
521
|
{
|
522
|
//System.out.println("url: " + u.toString());
|
523
|
char istreamChar;
|
524
|
int istreamInt;
|
525
|
InputStreamReader istream = new InputStreamReader(u.openStream());
|
526
|
StringBuffer serverResponse = new StringBuffer();
|
527
|
while((istreamInt = istream.read()) != -1)
|
528
|
{
|
529
|
istreamChar = (char)istreamInt;
|
530
|
serverResponse.append(istreamChar);
|
531
|
}
|
532
|
|
533
|
return serverResponse.toString();
|
534
|
}
|
535
|
}
|