Example of request.getparameter(), Retrieve Parameters from HTML Form

Let us see how to use request.getParameter() method in the servlet class, to retrieve the input values from HTML page.  Friends it is base concept on retrieving the input data, so observe very carefully, also this is the first example we are seeing on retrieving the values form the input pages.

Hmmm let us calculate sum of two numbers [ by taking these numbers from the input HTML page ]

Directory Structure

Files Required

• index.html
• OngetParameter.java
• web.xml

index.html

<font face="verdana" size="2px">
   <form action="sum" method="post">
       Number1:<input type="text" name="n1"><br>
       Number2:<input type="text" name="n2"><br>
       <input type="submit" value="Calculate Sum">
  </form>
</font>

OngetParameter.java

package java4s;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class OngetParameter extends HttpServlet  
{
    protected void doPost(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
	{
		PrintWriter pw=res.getWriter();
		res.setContentType("text/html");

		String n1=req.getParameter("n1");
		String n2=req.getParameter("n2");

		int result=Integer.parseInt(n1)+Integer.parseInt(n2);		
		pw.println("Sum of two numbers " +result);
		pw.close();

	}

}

web.xml

<web-app>

    <servlet>
       <servlet-name>sumOfTwoNumbers</servlet-name>
       <servlet-class>java4s.OngetParameter</servlet-class>
    </servlet>

    <servlet-mapping>
       <servlet-name>sumOfTwoNumbers</servlet-name>
       <url-pattern>/sum</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
       <welcome-file>index.html</welcome-file>
    </welcome-file-list>

</web-app>

Explanation:

• Once we run the application, browser will display index.html as front page.  Because we have given index.html in welcome file list [ line number 14 in web.xml ]
• Enter input values and press ‘Calculate Sum‘ button
• Now come to OngetParameter.java > just retrieve the input values like req.getParameter(“n1”) & req.getParameter(“n2”)
• getParameter() is the method in request object, which returns String value always
• So convert that string output to Integer [ line number 21]
• Integer.parseInt(-String-) gives integer value
• Output

Output

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.