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Request forwarding and redirection
2022-07-06 05:58:00 【The corner of fufu】
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There is login verification and display home page in the web page , How to jump and interact ?
Two Servlet(JSP) There are two ways to jump between :
- Request forwarding
- Response redirection
One 、 Request forwarding
It's a server jump , Only one request will be generated
// Realize the function of request forwarding
request.getRequestDispatcher("/direct/index").forward(request,response);
Request forwarding : The address is direct/check
Console output
Two 、 Response redirection
Redirection is browser side jump , There will be two requests
// Response redirection needs to be increased contextPath
response.sendRedirect("/servlet_advanced/direct/index");
Response redirection : The address is entered as direct/check
After resetting, the address changes to direct/index
Console output
3、 ... and 、 Set request custom properties
Request permission to create custom attributes
Set request properties
request.setAttribute("username", "admin");
Get request properties
String name = (String)request.getAttribute("username");
1、 Request forwarding
Request only once , Can get admin attribute
2、 Response redirection
Response redirection , Ask twice , First destroyed , Get the property value as null
Four 、 Program page
1、CheckLoginServlet.java
package com.ssyt.servlet.direct;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/** * Servlet implementation class CheckLoginServlet */
@WebServlet("/direct/check")
public class CheckLoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/** * @see HttpServlet#HttpServlet() */
public CheckLoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println(" User login successful ");
request.setAttribute("username", "admin");
// Realize the function of request forwarding
request.getRequestDispatcher("/direct/index").forward(request,response);
// Response redirection needs to be increased contextPath
//response.sendRedirect("/servlet_advanced/direct/index");
}
}
2、IndexServlet.java
package com.ssyt.servlet.direct;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/** * Servlet implementation class IndexServlet */
@WebServlet("/direct/index")
public class IndexServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/** * @see HttpServlet#HttpServlet() */
public IndexServlet() {
super();
// TODO Auto-generated constructor stub
}
/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String name = (String)request.getAttribute("username");
response.getWriter().println("This is index page!current username is " + name + ".");
}
}
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