by Dinesh Thakur Category: Servlet with MySql Database

This function 'Comparison Operator' will check the comparison between two expressions.

First i made a table named 'sal' with required fields and values into a database named 'dbase' within the reference of mySql(php myAdmin).then i import all the java packages from the java library. I made a class named 'MySqlComparisonOperatorJavaServlet' extends the 'HttpServlet'. I use serviceMethod() which is use to getting the request from the doGet()method for output on a web server. Then i loaded all the required drivers for database accessing. I use variables that will be used to database connectivity. First i declare 'connection' (this variable will create a link between a database and the java code). I declare 'resultSet'(this variable will be the responsible for getting value from required fields like columns and rows).then i declare 'preparedStatement' this variable will use to execute the selected query like executeQuery() as (SELECT last_name, salary FROM sal WHERE salary <= 8000"). Now i use the doGet()Method which will bring the output on web browser.

To getting output in a tabular form on a web browser i use 'HTML' code and tags that will bring output in a manner way.

 

EXAMPLE
 
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 MySqlComparisonOperatorJavaServlet 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 last_name, salary FROM sal WHERE salary <= 8000");
         rs = ps.executeQuery();
             String title = "Employee's Info With Comparison Condition";
         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" + "<h3 align=\"center\">" + title + "</h3>\n" + "<ul>\n" +
             "<table width=\"50%\" border=\"1\" align=\"center\">\n" + "<th>Last Name</th><th>Salary</th>\n"+ "</body> </html>");
         while(rs.next())
           {
             String l_name = rs.getString("last_name");
                 int sal = rs.getInt("salary");
                 disp.println("<tr><td align=\"center\">"+ l_name +          "<td align=\"center\">"+ sal +"</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>MySqlComparisonOperatorJavaServlet</servlet-name>
   <servlet-class>MySqlComparisonOperatorJavaServlet</servlet-class>
</servlet>
<!-- servlet mapping -->
<servlet-mapping>
   <servlet-name>MySqlComparisonOperatorJavaServlet</servlet-name>
   <url-pattern>/MySqlComparisonOperatorJavaServlet</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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