Access DatabaseYou can use any database of your choice but for this article I will stick with Microsoft Access database on a Windows platform.
Create a new Access database with the name of 'odbc_exmp.mdb' and create a table 'Names' containing three fields 'ID', 'first_name' and 'last_name' where 'ID' is the primary key :
Names - Table
Go to the control panel and create a new DSN ( Data Source Name ) 'odbc_exmp' for it and point it to the path of your database on your computer.
Populate the 'Names' table with any values like the following so that we can display the records later :
Names - Table
DisplayServletCreate a new DisplayServlet.java file in the /APP_NAME/WEB-INF/classes/com/stardeveloper/servlets/db/ folder. Note /APP_NAME/ is the path of your application within your application server, in Tomcat 4.0 /APP_NAME/ will be /CATALINA_HOME/webapps/star/ where 'star' is the name of the application.
Copy and paste the following code into DisplayServlet.java file and compile it :package com.stardeveloper.servlets.db; import java.sql.*;import java.io.*;import javax.servlet.*;import javax.servlet.http.*; public class DisplayServlet extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.print(""); out.print(""); out.print(""); out.print(""); out.close(); } public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.print(""); out.print(""); out.print("
"); out.print("ID\tFirst "); out.println("Name\tLast Name\n"); // debugging info long time1 = System.currentTimeMillis(); // connecting to database Connection con = null; Statement stmt = null; ResultSet rs = null; try { Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); con = DriverManager.getConnection("jdbc:odbc:odbc_exmp"); stmt = con.createStatement(); rs = stmt.executeQuery("SELECT * FROM Names"); // displaying records while(rs.next()) { out.print(rs.getObject(1).toString()); out.print("\t"); out.print(rs.getObject(2).toString()); out.print("\t\t"); out.print(rs.getObject(3).toString()); out.print("\n"); } } catch (SQLException e) { throw new ServletException("Servlet Could not display records.", e); } catch (ClassNotFoundException e) { throw new ServletException("JDBC Driver not found.", e); } finally { try { if(rs != null) { rs.close(); rs = null; } if(stmt != null) { stmt.close(); stmt = null; } if(con != null) { con.close(); con = null; } } catch (SQLException e) {} } // debugging info long time2 = System.currentTimeMillis(); out.print("Search took : "); out.print( (time2 - time1) ); out.print(" ms.
"); out.print("Start your application server and point your browser to http://localhost:8080/star/servlet/com.stardeveloper.servlets.db.DisplayServlet to see the Servlet display records on your computer. To see the demo please move on to the last page of this article.
Steps of Connecting to DatabaseIn the previous page we developed a Servlet 'DisplayServlet' which extends HttpServlet class and overrides doGet() and doPost() methods. In the doGet() method we display a Form to the user to click, after which he will be shown records from our 'odbc_exmp.mdb' database. Nothing much to talk about yet. In doPost() method we make a connection to the database and iterate through it's records. This is the method which needs more explanation.
