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Servlet allows you to write and read from a database using JDBC. JDBC helps provide the Java database connectivity application programming interface (API) available in the Java software. Using JDBC in servlet includes setting up the environment, creating a table in the database, and establishing a connection with the database. Before establishing connection with the database, you need to install a database on your machine. Then, you need a database driver to set the environment and locate the database.

After locating the database you need to assign appropriate permissions to connect to the database. The establishment of connection with the database is based on the login information and password entered by the user. The type of permissions assigned may vary with the type of driver used to establish the connection management sytem, the servlet executes the query against the database and displays the result of the query.

Using JDBC in Java servlet enables you to develop servlets that can perform database connectivity. The JDBC code in the servlet file creates a database connection, executes the client queries and closes the connection after the response to the client queries is sent to the clients.

The following program shows the Html file, which invokes the Java servlet that uses JDBC to maintain database connection and executes the SQL queries:

HTML File to Invoke the Java Servlet

<HTML> <HEAD><TITLE>Connection Servlet and JDBC</TITLE></HEAD> <BODY> <CENTER><H1>Using JDBC In Servlet</H1></CENTER><HR><BR> <FORM Method=post Action="http://localhost:8080/examples/servlet/JDBCDemo"> Admission No: <Input Type=Text Name=adm_no> <Input Type=Submit Value= "Search "> </FORM> </BODY> </HTML>

The HTML file accepts an integer parameter in the text box and passes it to the Java servlet when the Submit Query button is clicked.

Diagram 24.20 shows the output of the HTML file on the Web browser.

Diagram 24.20 HTML File for Invoking Java Servlet

The Submit query button on the HTML web page invokes the Java servlet. A databaase connection is created by the Java servlet and returns the information of student with the integer value passed in the text box.

The output of the Java servlet that displays the information of the student is shows in Diagram 24.21.

The following program code shows using JDBC in Java Servlet:

/*
===========================================================
File Name : JDBCDemo.java
WebSite : http://javaproglang.blogspot.in/
Facebook : https://www.facebook.com/AdvanceJavaProgramming
Twitter ID : https://twitter.com/AdvanceJava
Created By : Bintu Chaudhary
===========================================================
*/
import java.io.*;
import java.sql.*;
import javax.naming.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class JDBCDemo extends HttpServlet
{
        public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
        {
                res.setContentType("text/html");
                PrintWriter pr=res.getWriter();

                String adm_no=req.getParameter("adm_no");

                try
                {
                        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                        Connection con=DriverManager.getConnection("jdbc:odbc:MyDsn");
                        Statement stat=con.createStatement();
                        ResultSet rs=stat.executeQuery("Select * from SchoolClasses Where Admission_No="+adm_no);

                        pr.println("<HTML>");
                        pr.println("<Head><Title>Using JDBC In Servlet</Title></Head>");
                        pr.println("<Body>");
                        pr.println("<Center><H1>Using JDBC In Servlet</h1><HR><BR>");
                        pr.println("<Table Border=1>");
                        pr.println("<Tr><Th>Class</Th><Th>RollNo</Th><Th>Name</Th><Th>Father's Name</Th><Th>DOB</Th><Th>City</Th></Tr>");

                        while(rs.next())
                        {
                                String clas=rs.getString("Class");
                                String rollno=rs.getString("Roll_No");
                                String name=rs.getString("Name");
                                String fname=rs.getString("Father_Name");
                                String dob=rs.getString("DOB");
                                String city=rs.getString("City");

                                pr.println("<Tr><Td>"+clas+"</Td>");
                                pr.println("<Td>"+rollno+"</Td>");
                                pr.println("<Td>"+name+"</Td>");
                                pr.println("<Td>"+fname+"</Td>");
                                pr.println("<Td>"+dob+"</Td>");
                                pr.println("<Td>"+city+"</Td></Tr>");
                        }
                        pr.println("</Table></Center>");
                        pr.println("</Body></HTML>");
                }
                catch(Exception e)
                {
                        pr.println("adm_no"+e);
                }
        }
}

The above code creates a Java servlet that can maintain database connection and execute SQL queries using JDBC.

Diagram 24.21 Using JDBC in Servlet

Java Servlet Programming

Creating Java Servlets (Compiling and Running a Java Servlet)

Generic and Http Servlets

Calling a servlet from within an HTML page

Using JDBC In Servlet

User Authentication Form using Java Servlet

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Using JDBC In Java Servlet Programming

Java Servlet Programming

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