ServletRequest
or HttpServletRequest
object has a map object that maps parameter name and its value. By accessing this map we can check if a parameter was passed in servlet request. Let’s see the example below.
package org.kodejava.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet(name = "ParameterCheck", urlPatterns = "/parameter-check")
public class ParameterCheck extends HttpServlet {
protected void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
// Check if username parameter exists
if (req.getParameterMap().containsKey("username")) {
String username = req.getParameter("username");
System.out.println("username = " + username);
}
// Check if password parameter exists
if (req.getParameterMap().containsKey("password")) {
String password = req.getParameter("password");
System.out.println("password = " + password);
}
}
}
Maven dependencies
<!--https://search.maven.org/remotecontent?filepath=javax/servlet/javax.servlet-api/4.0.1/javax.servlet-api-4.0.1.jar-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
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