Example on getParameterNames() method of Servlet Request Object

So far we have worked on getParameter(), let us see how to use getParameterNames() method. With getParameter() we are able to find parameter values by passing parameter name, just like..

In html:
<input type=”text” name=”n1″>

In Java:
String val=req.getParameter(“n1”);

Parameter name – n1
Parameter value – val

If a client send the data to the servlet, that data will be available in the object of HttpServletRequest interface. In case of getParameter() method we have to pass input parameter name and it will give the value. If you are not aware of input parameter name ? or if you have 50+ input values its really tedious to use getParameter() method.

That’s why this getParameterNames() came into picture 🙂

Directory Structure

Files Required

• index.html
• OngetParameterNames.java
• web.xml

index.html

<font face="verdana" size="2px">
    <form action="onPM" method="post">
        Name:<input type="text" name="name">
        Country:<input type="text" name="country">
        <input type="submit" value="Submit">
     </form>
</font>

OngetParameterNames.java

package java4s;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

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

		Enumeration en=req.getParameterNames();

		while(en.hasMoreElements())
		{
			Object objOri=en.nextElement();
			String param=(String)objOri;
			String value=req.getParameter(param);
			pw.println("Parameter Name is '"+param+"' and Parameter Value is '"+value+"'");
		}		
			pw.close();	
	}
}

web.xml

<web-app>

   <servlet>
     <servlet-name>onParameterNames</servlet-name>
     <servlet-class>java4s.OngetParameterNames</servlet-class>
   </servlet>

   <servlet-mapping>
     <servlet-name>onParameterNames</servlet-name>
     <url-pattern>/onPM</url-pattern>
   </servlet-mapping>

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

</web-app>

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.