by Dinesh Thakur Category: Servlet with MySql Database

This Operator used when a NULL value has to retrieve from table or Database.

I Made a table Named 'mgr' Into a database named 'dbase' within the reference of mySql(php myAdmin). Then i import all the mandatory java packages from the java library. Then i made a class named 'MySqlNullCondition', which extends the 'HttpServlet'. I use serviceMethod() which is responsible for getting request from the doGet() method for Output on a web browser. After, then i loaded all required drivers that necessary for database accessing. The next move i declare variable those objects will create a criteria to use database i use 'connection' variable (which will be use to create a connection between database and the java code (actual code). The next variable will be the 'resulSet' (this will be responsible for getting value from the desired column and rows as required). And the next one will be the 'preparedStatement' that will use to executing the query like executeQuery() as (SELECT name,salary,manager_id FROM mgr WHERE manager_id is NULL). At the last instance i use doGet()Method which will use to get output on a web Browser.

We use a tabular form concept. For this kind of requirement, we use ‘HTML’ coding and some of tags to use Output in Designer look to show on a 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 MySqlNullCondition 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 name,salary,manager_id FROM mgr WHERE manager_id is NULL");
                   rs = ps.executeQuery();
                               String title = "Employee's Info With Using of Null 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>Name</th><th>Salary</th><th>Manager Id</th>\n"+ "</body> </html>");
                   while(rs.next())
                      {
                           String nm = rs.getString("name");
                                       int sal = rs.getInt("salary");
                                       int m_id=rs.getInt("manager_id");
                                      disp.println("<tr><td align=\"center\">" + nm +  "<td align=\"center\">" + sal +"<td align=\"center\">" + m_id +"</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>MySqlNullCondition</servlet-name>
   <servlet-class>MySqlNullCondition</servlet-class>
</servlet>
<!-- servlet mapping -->
<servlet-mapping>
   <servlet-name>MySqlNullCondition</servlet-name>
   <url-pattern>/MySqlNullCondition</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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