The getQueryString() method is defined in the HttpServletRequest interface, which is used to retrieve the query string of the HTTP request. A query string is the string on the URL to the right of the path to the servlet. Using this a programmer can know the data which is sent from the client(when a form is submitted)
What is a Query String?
A Query String is a String which is appeneded to the URL containing the form fields and data which is entered by the user. It will start with a ‘?’ and the fields are seperated by ‘&’
http://localhost:8080/ServletsTutorial/QueryStringExample?firstName=Java&lastName=InterviewPoint
Here we can see that there are two Form fields firstName and lastName appended as query string as values and two fields are seperated by &.
Lets now see the complete example to have a better understanding.
Form.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!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>Query String Example</title>
</head>
<body>
<form method="GET" action="./QueryStringExample">
First Name : <input type="text" name="firstName"/></br>
Last Name : <input type="text" name="lastName"/></br>
<input type="submit"></br>
</form>
</body>
</html>QueryStringExample.java
package com.javainterviewpoint;
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 QueryStringExample extends HttpServlet
{
public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
{
res.setContentType("text/html");
PrintWriter out = res.getWriter();
String queryString = req.getQueryString();
out.println("Query String passed is : " + queryString);
out.close();
}
}
We will be calling getQueryString() method of the request to get the query string.
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee%20http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>ServletsTutorial</display-name>
<servlet>
<servlet-name>QueryStringExample</servlet-name>
<servlet-class>com.javainterviewpoint.QueryStringExample</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>QueryStringExample</servlet-name>
<url-pattern>/QueryStringExample</url-pattern>
</servlet-mapping>
</web-app>Run the Form.jsp page
After filling the FirstName and LastName, click on the submit button to get the queryString.
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