In this tutorial you will learn about how to use the ln() function in math function of mysql with java servlet.
Mysql LN() Function Example Using Java Servlet
In this tutorial you will learn about how to use the ln() function in math function of mysql with java servlet.
LN() function in MySql the real number is passed as an argument into its parameter and gives its natural log value. This function acts as the inverse of the function exp(). If the value of the number is given to less than or equals to 0 this function returns null value.
Syntax :
ln(num);
Here num is a real number of which you want the log value.
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlLnServlet which extends the HttpServlet class. In the body of class I overridden the method doGet() and created an objects of HttpServletRequest and HttpServletResponse into its parameter. Inside the doGet() method first I set the mime type that in which format the browser will show the output. In the next line I used the getWriter() method of ServletResponse interface with the object of HttpServletResponse. HttpServletResponse interface extends this method from the ServletResponse. In Next step I am taking inputs using the getParameter() method of ServletRequest with the object of HttpServletRequest. In continue we have to establish a connection between java code and database system. So, since I am using Mysql in the example given below therefore, I am loading the driver of mysql and make a connection by using the getConnection() method of DriverManager class. It returns a Connection. Further I passed the query "SELECT LN("+lg+")"; (Here 'lg' is a variable that stores the value given by the user in their respective textfields.) into the parameter of prepareStatement() method of Connection interface which gives an object of PreparedStatement interface. In the next line I used the executeQuery() method of PreparedStatement interface which returns a ResultSet object that holds the result of query. At last I have extracted the result from the ResultSet object.
Example :
ln.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>LN() Function</title> </head> <body> <form method="get" action="MysqlLnServlet"> <table> <tr> <td>Enter a number</td><td><input type="text" name="text1"/></td> </tr> <tr> <td></td><td align="center"> <input type="submit" value ="ok"/></td> </tr> </table> </form> </body> </html>
MysqlLnServlet.java
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 MysqlLnServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
double lg = Double.parseDouble(request.getParameter("text1"));
String className = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://192.168.10.13";
String user = "root";
String password = "root";
Connection con;
PreparedStatement ps;
ResultSet rs;
try
{
Class.forName(className);
con = DriverManager.getConnection(url, user, password);
String sql = "SELECT LN("+lg+")";
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next())
{
double result = Double.parseDouble(rs.getString(1));
out.println("value of ln("+lg+") = "+result);
}
}
catch(SQLException sx)
{
out.println(sx);
}
catch(ClassNotFoundException cx)
{
out.println(cx);
}
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>mysqlMathematicalFunction</display-name> <servlet> <servlet-name>MysqlLnServlet</servlet-name> <servlet-class>MysqlLnServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlLnServlet</servlet-name> <url-pattern>/MysqlLnServlet</url-pattern> </servlet-mapping> </web-app>
Output
When you will execute the above example you will get the output as :
1.
2. When you will enter the value.
3. When you will click on 'ok' button you will get the output as :
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