In this tutorial you will learn about how to use rand() math function of mysql with java servlet.
Mysql RAND() Function Example Using Java Servlet
In this tutorial you will learn about how to use rand() math function of mysql with java servlet.
RAND() function in MySql gives a randomly generated value in between 0 to 1. How many times you will call this function it repeats a sequence of column values ( between 0 to 1) randomly.
Syntax :
rand();
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlRandServlet 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 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 RAND ()"; 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 :
MysqlRandServlet.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 MysqlRandServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
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 RAND()";
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next())
{
double rd = Double.parseDouble(rs.getString(1));
out.println("<html>");
out.println("<form>");
out.println("<table>");
out.println("<tr><td>rand()</td></tr>");
out.println("<tr><td>"+rd+"</td></tr>");
out.println("</table>");
out.println("</form>");
out.println("</html>");
}
}
catch(ClassNotFoundException cx)
{
out.println(cx);
}
catch(SQLException sx)
{
out.println(sx);
}
}
}
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>MysqlRandServlet</servlet-name> <servlet-class>MysqlRandServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlRandServlet</servlet-name> <url-pattern>/MysqlRandServlet</url-pattern> </servlet-mapping> </web-app>
Output
When you will execute the above example you will get the output as :
1.
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