This Function Will Returns the base-2 logarithm of the passed numeric expression.
I use to made a database first named ‘dbase’ within the reference of mySql(php myAdmin). Then i import all important java packages from java library. Then i made a class named ‘ MySqlLOG2Function’ extends ‘HttpServlet’. Then i use service()Method this will be responsible for the getting the request from the doGet()Method for output. Then i loaded all the required drivers for the database accessing. Then i use to set variables like i use first variable ‘connection’ that will be responsible for the creating a link between database and the java code. Then i use ‘resultSet’ this will use to get value from the selected columns and the rows from table. I use here ‘preparedStatement’ that use to executing the selected query like executeQuery() as (Select LOG2(512)). Then in last phase i use doGet()Method that will provide the output on the web browser.
To feel look good the result 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 MySqlLOG2Function 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 LOG2(512)");
rs = ps.executeQuery();
String title = "Using LOG2(LOGRITHM) 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>Value</th>\n"+ "</body> </html>");
while(rs.next())
{
String val = rs.getString(1);
disp.println("<tr><td align=\"center\">" + val +"</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>MySqlLOG2Function</servlet-name>
<servlet-class>MySqlLOG2Function</servlet-class>
</servlet>
<!-- servlet mapping -->
<servlet-mapping>
<servlet-name>MySqlLOG2Function</servlet-name>
<url-pattern>/MySqlLOG2Function</url-pattern>
</servlet-mapping>
Dinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular