Overview
In this article I'll explain each step you need to know to display records from the
database using Servlets. The steps for displaying records in JSP pages and Java Beans are
almost the same. We will first build a small example Microsoft Access database, create
a DSN for it and using JDBC ( Java Database Connectivity ) driver connect with it and
display the records from a given table. Since 80% of your time developing applications
will be spent on interacting with databases, you should pay utmost importance to this
article.
Access Database
You 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
DisplayServlet
Create 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("<html><head>");
out.print("</head><body>");
out.print("<form action=\"");
out.print( req.getRequestURI() );
out.print("\" method=\"post\">");
out.print("<input type=\"submit\" ");
out.print("value=\" \"> ");
out.print("Display Records</form>");
out.print("</body></html>");
out.close();
}
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.print("<html><head>");
out.print("</head><body>");
out.print("<code><pre>");
out.print("<font color=green>ID\tFirst ");
out.println("Name\tLast Name\n</font>");
// 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("</pre></code>");
out.print("<p>Search took : ");
out.print( (time2 - time1) );
out.print(" ms.</p>");
out.print("<p\"><a href=\"");
out.print( req.getRequestURI() );
out.print("\">Back</a></p>");
out.print("</body></html>");
out.close();
}
}
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 Database
In 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.
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