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accessing values from servlets to jsp

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posted 15 years ago

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hi i am new to jsp and i have wriiten a code to access values from servlets to jsp..

kindly tell me what is my mistake???
Reading.jsp

and my servlet is Simpe.java

package myServlets;

import myServlets.Data;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.util.*;

public class Simple extends HttpServlet{
	
 public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException,IOException
    {
		String url = "jdbc:postgresql://localhost/Books";
	    `      Connection con=null;
		ResultSet rs;
		String s;
		Statement st=null;

String sqlstr = "SELECT \"BillMonthYear\",\"Principal\",\"Interest\",\"Tax\",\"AptRent\",\"CarLoan\","+ 
	       "\"EPB\", \"ATT\", \"ComcastISP\", \"Vonage\",\"HealthInsurance\",\"CarInsurance\","+ 
	       "\"PMI\", \"BankOfAmerica\", \"DCU VISA\", \"DiscoverFlag\", \"Discovermiles\","+ 
	       "\"TrustVISA\", \"HOA Fee\" FROM \"BookSchema\".\"Bill\"";
	
try 
{
con = DriverManager.getConnection(url,"postgres", "admin123");
st = con.createStatement();
rs = st.executeQuery(sqlstr);

List<Data> b=new ArrayList<Data>();	
while (rs.next())	
{
Data bm=new Data();	
bm.setBillMonthYear(rs.getString(1));
bm.setPrincipal(rs.getString(2));
bm.setInterest(rs.getString(3));
bm.setTax(rs.getString(4));
bm.setAptRent(rs.getString(5));
bm.setCarLoan(rs.getString(6));
bm.setEPB(rs.getString(7));
bm.setATT(rs.getString(8));
bm.setComcastISP(rs.getString(9));
bm.setVonage(rs.getString(10));
bm.setHI(rs.getString(11));
bm.setCI(rs.getString(12));
bm.setPMI(rs.getString(13));
bm.setBOA(rs.getString(14));
bm.setDCUVISA(rs.getString(15));
bm.setDiscoverFlag(rs.getString(16));
bm.setDiscovermiles(rs.getString(17));
bm.setTrustVISA(rs.getString(18));
bm.setHOAFee(rs.getString(19));
   b.add(bm);           
 }
request.setAttribute("b",b);
	ServletContext sc = getServletContext();
	    RequestDispatcher dispatcher = request.getRequestDispatcher("/Reading.jsp");
		dispatcher.forward(request,response);
		rs.close();
}
catch(Exception ex) 
{
System.err.println("Exception: " + ex.getMessage());
}
finally
{
try
{
if (st!=null)
st.close();
}
catch(Exception ep)
{
ep.printStackTrace();
}
try
{
if (con!=null)
con.close();
}
catch(Exception ie)
{
ie.printStackTrace();
}
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws ServletException,IOException{	
 try
  {
  doPost(request,response);
  }
  catch(Exception ie)
  {
  ie.printStackTrace();
  }
  }
  }

i have wriiten accessor methods in another class caled Data.java which is not a servlet.......

i am confused whether how do i access values from servlets to jsp...and have I written a proper code to send the data in jsp file??

Bear Bibeault

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posted 15 years ago

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With all that poorly formatted and unnecessary code, I cannot tell.

Please post again, showing only the code that's necessary to answer your question (how you are setting up the data in the servlet, and consuming it in the JSP) with proper formatting and indentation.

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maggie karve

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posted 15 years ago

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maggie joseph wrote:hi i am new to jsp and i have wriiten a code to access values from servlets to jsp..

kindly tell me what is my mistake???
Reading.jsp
//this is my jsp which will display the values in a table foramt containing 19 columns...

<html> <table border="1"> <%@ page import="java.util.*" %> //these are the 19 columns for table display.... <tr> <td>BillMonthYear</td> <td>Principal</td> <td>Interest</td> <td>Tax</td> <td>AptRent</td> <td>CarLoan</td> <td>EPB</td> <td>ATT</td> <td>ComcastISP</td> <td>Vonage</td> <td>HealthInsurance</td> <td>CarInsurance</td> <td>PMI</td> <td>BankOfAmerica</td> <td>DCUVISA</td> <td>DiscoverFlag</td> <td>DiscoverMiles</td> <td>TrustVisa</td> <td>HOAFee</td> </tr> //here i want to get values from servlet...i dont know how to write a code here in following lines below to access each value from servlet....I need to use an iterator but i am probably not using it properly.... <tr> <td><%= request.getAttribute("b") %></td> <% Iterator <List> it=b.iterator(); while (it.hasNext()) { List d=it.next(); <%= d %> } %> </tr> </table>

and my servlet is Simple.java

package myServlets; import myServlets.Data; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; import java.util.*; public class Simple extends HttpServlet{ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException { String url = "jdbc:postgresql://localhost/Books"; Connection con=null; ResultSet rs; String s; Statement st=null; String sqlstr = "SELECT \"BillMonthYear\",\"Principal\",\"Interest\",\"Tax\",\"AptRent\",\"CarLoan\","+ "\"EPB\", \"ATT\", \"ComcastISP\", \"Vonage\",\"HealthInsurance\",\"CarInsurance\","+ "\"PMI\", \"BankOfAmerica\", \"DCU VISA\", \"DiscoverFlag\", \"Discovermiles\","+ "\"TrustVISA\", \"HOA Fee\" FROM \"BookSchema\".\"Bill\""; try { con = DriverManager.getConnection(url,"postgres", "admin123"); st = con.createStatement(); rs = st.executeQuery(sqlstr); List<Data> b=new ArrayList<Data>(); while (rs.next()) { Data bm=new Data(); bm.setBillMonthYear(rs.getString(1)); bm.setPrincipal(rs.getString(2)); bm.setInterest(rs.getString(3)); bm.setTax(rs.getString(4)); bm.setAptRent(rs.getString(5)); bm.setCarLoan(rs.getString(6)); bm.setEPB(rs.getString(7)); bm.setATT(rs.getString(8)); bm.setComcastISP(rs.getString(9)); bm.setVonage(rs.getString(10)); bm.setHI(rs.getString(11)); bm.setCI(rs.getString(12)); bm.setPMI(rs.getString(13)); bm.setBOA(rs.getString(14)); bm.setDCUVISA(rs.getString(15)); bm.setDiscoverFlag(rs.getString(16)); bm.setDiscovermiles(rs.getString(17)); bm.setTrustVISA(rs.getString(18)); bm.setHOAFee(rs.getString(19)); b.add(bm); } ///are the lines below right in try block??? request.setAttribute("b",b); ServletContext sc = getServletContext(); RequestDispatcher dispatcher = request.getRequestDispatcher("/Reading.jsp"); dispatcher.forward(request,response); rs.close(); } catch(Exception ex) { System.err.println("Exception: " + ex.getMessage()); } finally { try { if (st!=null) st.close(); } catch(Exception ep) { ep.printStackTrace(); } try { if (con!=null) con.close(); } catch(Exception ie) { ie.printStackTrace(); } } } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException{ try { doPost(request,response); } catch(Exception ie) { ie.printStackTrace(); } } }
i have wriiten accessor methods in another class called Data.java which is not a servlet.......

i am confused whether how do i access values from servlets to jsp...and have I written a proper code to send the data in jsp file??

Bear Bibeault

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posted 15 years ago

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Is that really how you indent your code?

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maggie karve

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posted 15 years ago

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sir kindly tell me how do i do it???

David Newton

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posted 15 years ago

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Put spaces before the first non-space character until elements at the same depth line up. Like this:and

package com.princetonecom.sp.businessobject;

public class Simple extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException,IOException
	{
		String url = "jdbc:postgresql://localhost/Books";
		Connection con=null;
		ResultSet rs;
		String s;
		Statement st=null;

try 
		{
			con = DriverManager.getConnection(url,"postgres", "admin123");
			st = con.createStatement();
			rs = st.executeQuery(sqlstr);

List<Data> b=new ArrayList<Data>();	
			while (rs.next())	
			{
				Data bm=new Data();	
				bm.setBillMonthYear(rs.getString(1));
				bm.setPrincipal(rs.getString(2));
				bm.setInterest(rs.getString(3));
				bm.setTax(rs.getString(4));
				bm.setAptRent(rs.getString(5));
				bm.setCarLoan(rs.getString(6));
				bm.setEPB(rs.getString(7));
				bm.setATT(rs.getString(8));
				bm.setComcastISP(rs.getString(9));
				bm.setVonage(rs.getString(10));
				bm.setHI(rs.getString(11));
				bm.setCI(rs.getString(12));
				bm.setPMI(rs.getString(13));
				bm.setBOA(rs.getString(14));
				bm.setDCUVISA(rs.getString(15));
				bm.setDiscoverFlag(rs.getString(16));
				bm.setDiscovermiles(rs.getString(17));
				bm.setTrustVISA(rs.getString(18));
				bm.setHOAFee(rs.getString(19));
				b.add(bm);           
			}
			request.setAttribute("b",b);
			ServletContext sc = getServletContext();
			RequestDispatcher dispatcher = request.getRequestDispatcher("/Reading.jsp");
			dispatcher.forward(request,response);
			rs.close();
		}
		catch(Exception ex) 
		{
			System.err.println("Exception: " + ex.getMessage());
		}
		finally
		{
			try
			{
				if (st!=null)
					st.close();
			}
			catch(Exception ep)
			{
				ep.printStackTrace();
			}
			try
			{
				if (con!=null)
					con.close();
			}
			catch(Exception ie)
			{
				ie.printStackTrace();
			}
		}
	}

public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
		try {
			doPost(request, response);
		} catch (Exception ie) {
			ie.printStackTrace();
		}
	}
}

See the difference?

David Newton

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posted 15 years ago

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No, that is not correct. It's easy to tell if it's correct--does it work?

maggie karve

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posted 15 years ago

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no its not working.....

David Newton

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posted 15 years ago

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Please see ItDoesntWorkIsUseless and TellTheDetails (those are links).

Albareto McKenzie

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posted 15 years ago

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Why are you doing this:
Iterator<List> it=b.iterator();
Shouldn't be Iterator<Data> it = b.iterator?
What's b? Is not defined anywhere.
Why do you use the iterator for a list? why not to use just a for(Data myData: request.getAttribute("b"))?
And the most important question... why to use Java code in a JSP where you can use JSTL and EL and forget about iterators, casting, etc...?

Read about the JSTL:

http://java.sun.com/products/jsp/jstl/reference/docs/index.html

and the Unified Expression Language:

http://java.sun.com/javaee/5/docs/tutorial/doc/bnahq.html

You will see that this:

can be changed to much simpler code:

By the way in your Data class you should have override the method toString, otherwise some strange string will appear in your browser.

praneel shah

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Posts: 17

posted 15 years ago

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use bean...........

maggie karve

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posted 15 years ago

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hey guys thanks a lot for your suggestions..it seems that i need to learn a lot still..and i dont know JSTL...

I have changed my code a bit...this is my servlet called Simple.java

try 
{
con = DriverManager.getConnection(url,"postgres", "admin123");
st = con.createStatement();
rs = st.executeQuery(sqlstr);

//passing and arraylist of the table rows ..Class Data.java is having getter and setter methods for getting the values and setting values from the database....
ArrayList<Data> b=new ArrayList<Data>();	
 	//for every row we go on setting the values of each column like BillMonthYear,Principal......HOAFee...
while (rs.next())	
{
Data bm=new Data();
bm.setBillMonthYear(rs.getString(1));
bm.setPrincipal(rs.getString(2));
bm.setInterest(rs.getString(3));
bm.setTax(rs.getString(4));
bm.setAptRent(rs.getString(5));
bm.setCarLoan(rs.getString(6));
bm.setEPB(rs.getString(7));
bm.setATT(rs.getString(8));
bm.setComcastISP(rs.getString(9));
bm.setVonage(rs.getString(10));
bm.setHI(rs.getString(11));
bm.setCI(rs.getString(12));
bm.setPMI(rs.getString(13));
bm.setBOA(rs.getString(14));
bm.setDCUVISA(rs.getString(15));
bm.setDiscoverFlag(rs.getString(16));
bm.setDiscovermiles(rs.getString(17));
bm.setTrustVISA(rs.getString(18));
bm.setHOAFee(rs.getString(19));

//adding the value of entire row in one object...so b gets the value of 4 rows ,since the loop runs 4 times,since i have 4 rows in my database table....i confirmed this by printing the value of the size of b..like S.O.P(b.size());
b.add(bm);     
 }
      //I am sending the values to jsp....
request.setAttribute("b",b);
ServletContext sc = getServletContext();
RequestDispatcher dispatcher = request.getRequestDispatcher("/Reading.jsp");
dispatcher.forward(request,response);
rs.close();

and in JSP i have made changes ....i am getting the values of the table but all 4 rows are having same value of the last row.....
How will I get all the values of all the rows..
my jsp Reading.jsp is as follows..

<tr>
<% ArrayList b = (ArrayList)request.getAttribute("b");
Iterator iter = b.iterator(); 
//here i am just getting the value of the last row...is there a problem in the way i am iterating...do i need to write something more to get all the values???
while (iter.hasNext()) 
{
Data element = (Data) iter.next();
out.println("<tr>");
out.println("<td>" + element.getBillMonthYear() + "</td>");
out.println("<td>" + element.getPrincipal() + "</td>");
out.println("<td>" + element.getInterest() + "</td>");
out.println("<td>" + element.getTax() + "</td>");
out.println("<td>" + element.getAptRent() + "</td>");
out.println("<td>" + element.getCarLoan() + "</td>");
out.println("<td>" + element.getEPB() + "</td>");
out.println("<td>" + element.getATT() + "</td>");
out.println("<td>" + element.getComcastISP() + "</td>");
out.println("<td>" + element.getVonage() + "</td>");
out.println("<td>" + element.getHI() + "</td>");
out.println("<td>" + element.getCI() + "</td>");
out.println("<td>" + element.getPMI() + "</td>");
out.println("<td>" + element.getBOA() + "</td>");
out.println("<td>" + element.getDCUVISA() + "</td>");
out.println("<td>" + element.getDiscoverFlag() + "</td>");
out.println("<td>" + element.getDiscovermiles() + "</td>");
out.println("<td>" + element.getTrustVISA() + "</td>");
out.println("<td>" + element.getHOAFee() + "</td>");
}
%>
	
</tr>
</table>

it just displays the last row of my database table..I want all 4 rows ..it is displaying same values of the last row in all four rows of my table........

David Newton

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posted 15 years ago

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Seems okay, although you should close your table row.

INDENT YOUR CODE.