by Dinesh Thakur Category: Servlet with MySql Database

This function to Use when a Maximum value of a selected field required (columns and rows).

I make a table named 'worker' into a database named 'dbase' within the reference of mySql(php my Admin). I import all the required java packages from java library. I use to make a class named ‘MySqlMAXFunction’, which extends the 'HttpServlet'. I use here service()Method which will use to get request from the doGet()Method. Then, i loaded all the required drivers for database accessing. Then, after i declare the variables like first i declare 'connection' this variable will be responsible for the creating link between the database and the java code. The other variable will be 'resultSet' this will does the job to fetching value from the desired column and rows as required. Then other one i declare 'preparedStatement' that will be responsible for executing the selected query like executeQuery() as (SELECT MAX(Salary) AS maxsal FROM worker)). After declaring all the variables i use doGet()Method which will use to get output on the web Browser.

I use 'HTML' code and tag in to the java code for output that will present the desired output in a tabular form on the web browser.

import java.io.IOException;

import java.io.PrintWriter;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MySqlMAXFunction extends HttpServlet
 {
     public void service(HttpServletRequest rq, HttpServletResponse rp)throws IOException, ServletException
       {
            rp.setContentType("text/html");
            PrintWriter disp = rp.getWriter();
            String driver = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql://localhost/dbase";
            String uid = "root";
            String psw = "root";
            Connection con=null;
            PreparedStatement ps = null;
            ResultSet rs;
            try
              {
                  Class.forName(driver);
                  con = DriverManager.getConnection(url,uid,psw);
                  ps=con.prepareStatement("SELECT MAX(Salary) AS maxsal FROM worker");
                  rs = ps.executeQuery();
               String title = "Using MAX(Maximum) Function";
                 String docType ="<!doctype html public \"-//w3c//dtd html 4.0 " + "transitional//en\">\n";
              disp.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" +
                 "<body bgcolor=\"#f4efef\">\n" + "<h1 align=\"center\">" + title + "</h1>\n" + "<ul>\n" +
              "<table width=\"50%\" border=\"1\" align=\"center\">\n" + "<th>Salary</th>\n"+ "</body> </html>");
                 while(rs.next())
                     {
                          String mx = rs.getString("maxsal");
                       disp.println("<tr><td align=\"center\">" + mx +"</td></tr>" );  
                     }     
              }       
                       catch(Exception e) 
                         {
                           e.printStackTrace();
                         }
                           disp.close();
     }
                       public void doPost(HttpServletRequest rq,HttpServletResponse rp)throws IOException,ServletException
                           {
                            doGet(rq,rp);
                           }
  }
WEB.xml
 
<servlet>
   <servlet-name>MySqlMAXFunction</servlet-name>
   <servlet-class>MySqlMAXFunction</servlet-class>
</servlet>
<!-- servlet mapping -->
<servlet-mapping>
   <servlet-name>MySqlMAXFunction</servlet-name>
   <url-pattern>/MySqlMAXFunction</url-pattern>
</servlet-mapping>




About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.



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