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Java Programming Code Examples

Java > Servlets Code Examples

Updating the client cache

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Updating the client cache package com.ack.web.servlet; import java.io.IOException; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class UpdatingTheClientCache extends HttpServlet { private Date lastUpdate; public void init() { lastUpdate = new Date( System.currentTimeMillis() ); } /** * This will see the server stuffing the Last-Modified header * into the response that is used by the client during * page reloads to check whether content on the server has * changed. * * Refer to how the If-Modified-Since and Last-Modified * headers used within the HTTP protocol * */ public long getLastModified( HttpServletRequest req ) { // round time down to the last second return lastUpdate.getTime() / 1000 * 1000; } public void doGet( HttpServletRequest req, HttpServletResponse res ) throws ServletException, IOException { boolean needToUpdate = false; // process some work if( needToUpdate ) { synchronized( this ) { lastUpdate = new Date( System.currentTimeMillis() ); } } res.getWriter().println( "done some work" ); } }