The javax.servlet.RequestDispatcher interface class help your servlet to call another servlet, JSP file, or HTML file from inside another servlet.
1) forward(ServletRequest request, ServletResponse response)
—>> forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server
2) include(ServletRequest request, ServletResponse response)
—>> includes the content of a resource (servlet, JSP page, HTML file) in the response
There are two main method in this interfaces
1) forward(ServletRequest request, ServletResponse response)
—>> forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server
2) include(ServletRequest request, ServletResponse response)
—>> includes the content of a resource (servlet, JSP page, HTML file) in the response
Example
Servlet class
This servlet class will do the include or forward based on the action from the user interfacepackage com.vinod;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MyServletDispatcher
*/
public class MyServletDispatcher extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MyServletDispatcher() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
if (request.getParameter("action") != null) {
String action = request.getParameter("action");
if (action.equalsIgnoreCase("include")) {
rd.include(request, response);
} else if (action.equalsIgnoreCase("forward")) {
rd.forward(request, response);
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MyServletDispatcher
*/
public class MyServletDispatcher extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MyServletDispatcher() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
if (request.getParameter("action") != null) {
String action = request.getParameter("action");
if (action.equalsIgnoreCase("include")) {
rd.include(request, response);
} else if (action.equalsIgnoreCase("forward")) {
rd.forward(request, response);
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
Test jsp (Dispatcher.jsp)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form name="input" action="http://localhost:8081/MyServletDispatcher"
method="get">
Enter Action: <input type="text" name="action"><input
type="submit" value="Submit">
</form>
</body>
</html>
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form name="input" action="http://localhost:8081/MyServletDispatcher"
method="get">
Enter Action: <input type="text" name="action"><input
type="submit" value="Submit">
</form>
</body>
</html>
index.JSP
Deploy and run the Dispatcher.jsp ( In this example using jetty server, so used jetty:run maven command to start the jetty server)
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