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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 450 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
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LVL 26

Accepted Solution

by:
Tomas Helgi Johannsson earned 1050 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
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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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