() is a request forwarding, and the front and back pages share a request;
() is a redirection, and the front and back pages are not a request.
() is run on the server side;
() is done by sending commands to the client browser.
So () is "transparent" to the browser;
And () is not.
The url in (String url) can only use absolute paths; while the url in (String url) can use relative paths. Because ServletRequest has the concept of relative paths; while ServletContext object has no concept of secondary.
The RequestDispatcher object gets the request request from the client and passes them to the servlet, html or jsp on the server. It has two methods:
forward(ServletRequest request,ServletResponse response)
For passing requests, one Servlet can receive a request request, and another Servlet can use this request request to generate a response. The request passed by request, the response is the information returned by the client. forward must be called before the response reaches the client, that is, before response body output has been flushed. If not, it will report an exception.
include(ServletRequest request,ServletResponse response)
Used to record and retain request and response, and the information indicating status in the response cannot be modified in the future.
If you need to transfer the request to an address in another Web App, you can follow the following methods:
1. Obtain the ServletConext object ((uripath)) of another Web App.
2. Call the (String url) method.
eg:(“”).forward(request,response);
Code example:
：
<%@ page language="java" import=".*" pageEncoding="GBK"%>
<% String path = (); String basePath = ()+"://"+()+":"+()+path+"/"; %>
My JSP '' starting page
<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3" />
<meta http-equiv="description" content="This is my page" />
<!--
<link rel="stylesheet" type="text/css" href="">
-->
<form action="servlet/session" method="post">
Username:<input type="text" name="username" />
Password:<input type="password" name="password" />
<input type="submit" />
</form>
：
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
public class session extends HttpServlet {
/**
* Constructor of the object.
*/
public session() {
super();
}
/**
* Destruction of the servlet.
*/
public void destroy() {
(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet.
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
/**
* The doPost method of the servlet.
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = "";
String password = "";
username = ("username");
password = ("password");
HttpSession session = ();
("username", username);
("password", password);
("name", username);
("pwd", password);
RequestDispatcher dis = ("/");
(request, response);
/*
("http://localhost:8080/sessiontest/");
*/
//This path must be written like this, and the relative path cannot be used as above
And if used, you cannot obtain the request object in the following section
//Because the same request is not used before and after, but the session is OK, because the session will exist until the user closes the browser
}
/**
* Initialization of the servlet.
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
：
<%@ page language="java" import=".*" pageEncoding="GBK"%>
<% String path = (); String basePath = ()+"://"+()+":"+()+path+"/"; %>
My JSP '' starting page
<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3" />
<meta http-equiv="description" content="This is my page" />
<!--
<link rel="stylesheet" type="text/css" href="">
-->
<% (""); String username = (String)("username");
String password = (String)("password");
String name = (String)("name");
String pwd = (String)("pwd");
("username " + username + " password " +password);
//If the above is used, you cannot get the name and pwd
("name " + name + "pwd "+ pwd);
%>