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Servlet JSP Best Practices (putting business logic behind a JSP)

Posted on 2007-11-22
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Last Modified: 2013-11-24
I have a Servlet called PoolTest.java (see attached) which simply grabs a connection from a database connection pool and prints out an html page with all the rows of a table.  As a general rule I've heard that you should seperate the dislpay (HTML) from the business logic (DB connectivity) as much as possible.  I have been able to create a JSP that does the same thing as this servlet but all the DB connection code is in the JSP!  I can't figure out how to serperate the two.  How do I do this?  Do I need to create a java bean?  I'm clueless, but want to get this right at the beginning before I get in too deep.  Many thanks.
import java.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.sql.*;
 

public class PoolTest extends HttpServlet {
 

	// Static class instantiation for the DB Connection Pool

	// As described from http://java.sun.com/developer/onlineTraining/Programming/JDCBook/conpool.html

	static {

		try {

		new pool.JDCConnectionDriver(

						"sun.jdbc.odbc.JdbcOdbcDriver",

						"jdbc:odbc:RREdb",

						"none", "none");

		}catch(Exception e){}

	}
 

	// Get a connection from the connection pool

  public Connection getConnection()

                      throws SQLException{

        return DriverManager.getConnection(

				"jdbc:jdc:jdcpool");

  }
 

	// Print out a simple HTML page with the rows of tblUsers

	public void doGet(HttpServletRequest request,

										HttpServletResponse response)

										throws IOException, ServletException

	{

		response.setContentType("text/html");

		PrintWriter out = response.getWriter();
 

		out.println("<html>\n");

		out.println("<body>\n");

		out.println("<table>\n");
 

		try {

			Statement stmt;

			Connection con;

			con = getConnection();

			stmt = con.createStatement();
 

			// Get data from tblUsers

			String query = "select userId, userName from tblUsers";

			ResultSet rs = stmt.executeQuery(query);

			ResultSetMetaData rsmd = rs.getMetaData();

			int numberOfColumns = rsmd.getColumnCount();

			int rowCount = 1;

			while (rs.next()) {

				out.println("<tr><td>" + rowCount + "</td>\n");

				for (int i = 1; i <= numberOfColumns; i++) {

					out.print("<td>" + rs.getString(i) + "</td>\n");

				}

				out.println("</tr>");

				rowCount++;

			}

			stmt.close();

			con.close();
 

		} catch(SQLException ex) {

			out.print("SQLException: ");

			out.println(ex.getMessage());

		}
 

		out.println("</table>");

		out.println("</body>");

		out.println("</html>");

	}

}

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Question by:burtonrhodes
3 Comments
 
LVL 4

Assisted Solution

by:jcoombes
jcoombes earned 150 total points
ID: 20334491
You might want to look at a framework such as Struts, JSF or Spring Web MVC...

The basic idea is yes, to move this logic into a bean somewhere, the various frameworks will then specify architectural patterns that determine how you surface and access them within your JSP code.

Cheers


JC
0
 
LVL 25

Accepted Solution

by:
Tomas Helgi Johannsson earned 350 total points
ID: 20334881
    Hi!

Use Beans with JSP. That is put all the DB related code into a BEAN and
call the bean from a JSP page
http://www.java2s.com/Code/Java/JSP/Beans.htm
http://www.java2s.com/Code/Java/JSP/Bean-Scope.htm

Regards,
  Tomas Helgi
0
 
LVL 3

Author Closing Comment

by:burtonrhodes
ID: 31410562
Both were correct, but the second answer was most helpful.   Many thanks!
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