HTML Form, Servlet and Database

SERVLETS AND JDBC

JDBC stands for Java Database Connectivity, which is a standard Java API for database connectivity between the Java programming language and a wide range of databases. The JDBC library includes APIs for

  • Making a connection to a database.
  • Creating query statements.
  • Executing queries in the database.
  • Viewing & Modifying the resulting records.

 

The JDBC API provides the following interfaces and classes −

  1. DriverManager: This class matches connection requests from the java application with the database driver and establishes a database Connection.
  2. Driver: This interface handles the communications with the database server.
  3. Connection: This interface has all methods to connect to the database and execute SQL queries
  4. Statement: interface to create SQL statements. Statement types:
    1. Static SQL statements (Statement interface),
    2. precompiled SQL statements (PreparedStatement interface), and
    3. stored SQL procedures (CallableStatement interface)
  5. ResultSet: These objects hold data retrieved from a database after executing an SQL query using Statement objects.
  6. SQLException: This class handles any errors that occur in a database application.

 

Working of JDBC

 

 

HTML, SERVLETS AND JDBC

Steps involved in creating an application to submit information to a servlet through form, accessing a database from the servlet and returning the result to client browser as a HTML page.

Steps:
Client Browser
  1. Create the HTML form to receive the required data
  2. On submit, send data to appropriate servlet in server
Server Servlet
  1. Receive the data from HTML form
  2. Construct the SQL Query
  3. Establish connection to the database and execute the query
  4. Retrieve result from the database.
  5. Close database connection.
  6. Create the HTML response page and send to client browser
Client Browser
  1. Display the HTML page received from the server.

 

 

Create HTML Form to submit data

<!– Simple program to demonstrate JDBC access –>

<!– Form to submit Department name to server –>

<!– html forms –>

<html>

<head>

<title>HTML Forms and Servlets</title>

<style>

label

{

font-family:vivaldi;

font-size:x-large;

letter-spacing:2px;

line-height:40px;

}

</style>

</head>

<body>

// Servlet Name – JDBC_DC

<form method=”GET” action=”JDBC_DC”>

<center>

<h2>HTML, Servlets and Database</h2></br>

<label>Enter Department Name  </label>

<input type=”text” Name=”DN” tabindex=1/>

<br/><br/>

<button class=”btn” type=”button ” >Get Code!!! </button>

</center>

</form>

</body>

</html>

 

 

// Servlet Program
// Servlet to receive form data, access database and generate response to client
// JDBC – Database name: XEPDB1
// Table: DC (name varchar(20), code varchar(20))

import java.io.*;

import java.util.*;

import java.lang.*;

import javax.servlet.http.*;

import javax.servlet.*;

import java.sql.*;

public class JDBC_DC extends HttpServlet

{

public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException

{

//setting the content type

res.setContentType(“text/html”);

//create the stream to write the data

PrintWriter pw=res.getWriter();

// Receive data from HTML Form

String D = req.getParameter(“DN”).trim();

//writing html in the stream

pw.println(“<html><body><h2>”);

pw.println(“<center>”);

pw.println(“Dept = “+D+”<br/>”);

try

{

// Establish connection with database

Connection conn = DriverManager.getConnection(“jdbc:oracle:thin:@//localhost:1521/XEPDB1”, “<username>”, “<password>”);

String qry = “SELECT * FROM DC WHERE name ='”+ D +”‘”;

PreparedStatement ps = conn.prepareStatement(qry);

ResultSet rs = ps.executeQuery();

while(rs.next())

pw.println(“Code = “+rs.getString(2)+”<br/>”);

}

catch (Exception e)

{

e.printStackTrace();

}

pw.println(“</center>”);

pw.println(“</h2></body></html>”);

//closing the stream

pw.close();

}

}

 

 

OUTPUT