How to Connect Servlet to the Database with Example

Let us see how to connect servelet application with (Oracle) database, for time being i am considering Oracle XE.  In our application i am going to display all the records from the table ‘Java4s‘.

• Make sure you have java4s table in the database with some data in it
• Make sure you have ojdbc14.jar file in your classpath and lib folder as well as [ why in two places ? 🙂 servlet will use ojdbc14.jar file which is in the classpath, for compiling the application, and ojdbc14.jar file in lib folder will be used at the time of running the servlet application], you can check the same in this figure…

Directory Structure

Files Required

• index.html
• ServletDatabaseConnect.java
• web.xml
• ojdbc14.jar

index.html

<form action="show" method="post">
  <font face="verdana" size="2">
     Enter Table Name :<input type="text" name="table"> 
                       <input type="submit" value="Display">
  </font>
</form>

ServletDatabaseConnect.java

package java4s;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletDatabaseConnect extends HttpServlet  
{
    protected void doPost(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
    {
        PrintWriter pw=res.getWriter();
        res.setContentType("text/html");        
        String tb=req.getParameter("table");    

        try
        {
             Class.forName("oracle.jdbc.driver.OracleDriver");
             Connection con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","system","admin");
             Statement st=con.createStatement();
             System.out.println("connection established successfully...!!");     

             ResultSet rs=st.executeQuery("Select * from "+tb);

             pw.println("<table border=1>");
                 while(rs.next())
                 {
                     pw.println("<tr><td>"+rs.getInt(1)+"</td><td>"+rs.getString(2)+"</td>"+
                                      "<td>"+rs.getString(3)+"</td></tr>");
                 }
             pw.println("</table>");
             pw.close();
        }
        catch (Exception e){
            e.printStackTrace();
        }

    }
}

web.xml

<web-app>

    <servlet>
        <servlet-name>ServletDBConnect</servlet-name>
        <servlet-class>java4s.ServletDatabaseConnect</servlet-class>    

    </servlet>

    <servlet-mapping>
            <servlet-name>ServletDBConnect</servlet-name>
            <url-pattern>/show</url-pattern>
    </servlet-mapping>

</web-app>

Output

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• Example of ServletConfig in Java Servlet
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• Example on getParameterMap() method of Servlet Request Object
• Example on getParameterNames() method of Servlet Request Object

::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.