Hi All,
I have JSP and Servlet that need to "talk" to each other. Actually I need to get record from database, fill it in JSP file. I have created Servlet that does the query and gets the result. I need those results to be shown on JSP file. In PHP I will just include the PHP file that does the query but I cannot find that simple way in JSP.
Trying to fix I came up with this method. When link is first clicked, it goes to servlet. Servlet processes it and posts results back to JSP. I'm using session to communicate. But Session is always null at JSP. Please see code and help me point out the error.
Also is this good method for table with thousands of data?
Thanks
Servlet code
package lam;
import javax.servlet.http.HttpServlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.http.HttpSession;
public class LAMHistory extends HttpServlet {
public void GetHistory(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
PrintWriter out = resp.getWriter();
try {
//Write a page with only rows. The code should be put between <table> </table> tags
ResultSet res = this.getAllTableRows();
int i; //iterator counter
//test variable - DELETE IT
int count = 0;
String pageContents = "";
ResultSetMetaData md = res.getMetaData();
int colCount = md.getColumnCount();
while (res.next()) {
if (count > 50) {
break;
}
//extract one row at a time and put it in table row
pageContents = pageContents + "<tr>";
for (i = 1; i <= colCount; i++) {
pageContents = pageContents + "<td>" + res.getString(i) + "</td>";
}
pageContents = pageContents + "<tr>";
count++;
}
//put on session
HttpSession session = req.getSession();
session.setAttribute("pageContents", pageContents);
RequestDispatcher dispatcher = req.getRequestDispatcher("/history.jsp");
if (dispatcher != null) {
//redirect to history page
dispatcher.forward(req, resp);
} else {
//redirect to error page
out.print("Sorry, redirection failed");
}
} catch (Exception e) {
e.printStackTrace();
out.print("Error: This servlet failed to do any processing!");
//redirect to error page
}
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//call histroy
this.GetHistory(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req, resp);
}
//get attributes
protected ResultSet getAllTableRows() {
//returns array of *FullName, LeaveApplicationDate, TotalLeaveDays, LeaveStatus, TakeAction*
DBClass db = new DBClass();
String sql = "SELECT user.full_name, application.start_date, application.end_date, application.working_days, "
+ "application.application_status WHERE user.employee_number=application.employee_number";
sql="SELECT * FROM application";
try{
ResultSet rs = db.dbSelect(sql);
return rs;
}catch(Exception e){
e.printStackTrace();
return null;
}
}
}//end classJSP file
<%--
Document : history
Created on : May 12, 2010, 4:11:19 PM
Author : smtangoo
--%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<link rel="stylesheet" type="text/css" href="history.css" />
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>History - NMC Leave Management Application</title>
</head>
<body>
<!-- Header Text, may be a logo -->
<center><h1 id="headertext">Welcome - LAM History</h1></center>
<!-- History table -->
<table align="center" border="1" cellpadding="5" id="historyTable">
<thead>
<tr>
<th class="headerRow">Full Name</th>
<th class="headerRow"> Leave Application Date</th>
<th class="headerRow">Total Leave Days</th>
<th class="headerRow">Leave Status</th>
<th class="headerRow">Take Action</th>
</tr>
</thead>
<tbody>
<!--
//fill in rows from history by getting contentPage attribute and echo it
-->
<%
//get string
//HttpSession session=req.getSession();
String historyPage = (String) request.getSession().getAttribute("contentPage");
out.println(historyPage);
%>
</tbody>
</table>
</body>
</html>