Idea creates a simple web project to analyze the difference between Servlet request forwarding and redirection

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Statement of needs:

// index.jsp page
 1 <%
 2   String basePath = request.getScheme()+":"+"//"+request.getServerName()+":"+request.getServerPort()+"/"
 3           +request.getServletContext().getContextPath()+"/";
 4 %>
 5 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 6 <html>
 7   <head>
 8 <title>ServletDemo addition operation</title>
 9   </head>
10   <body>
11 <%--action: Indicates the servlet path accessed --%>
12     <%out.print("basePath意味着：" + basePath);%>
13     <form action="<%=basePath%>ServletDemo1" method="post">
14       a: <input type="text" name="a"><br>
15       b: <input type="text" name="b"><br>
16       <input type="submit" value="计算"/><br>
17     </form>
18   </body>
19 </html>

// ServletDemo1.java

 1 import javax.servlet.ServletContext;
 2 import javax.servlet.ServletException;
 3 import javax.servlet.annotation.WebServlet;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import java.io.IOException;
 8 
 9 @WebServlet("/ServletDemo1")
10 public class ServletDemo1 extends HttpServlet {
11     @Override
12     public void init() throws ServletException {
13         System.out.println("init()方法");
14     }
15 
16     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
17         System.out.println("doPost()方法");
18         doGet(request, response);
19     }
20 
21     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
22         String a = request.getParameter("a" );
 23          String b = request.getParameter("b" );
 24          int sum = Integer.valueOf(a) + Integer.valueOf(b);
 25          request.setAttribute("sum " , sum);
 26          // Method 1: Write the PrintWriter object
 27  //         response.getWriter().print(sum);
 28          // Method 2: Request forwarding
 29  //         request.getRequestDispatcher("sum.jsp") .forward(request, response);
 30          // Method 3: Redirection 
31          ServletContext sc = request.getServletContext();
 32         sc.setAttribute("sum2", sum);
33         response.sendRedirect("sum2.jsp");
34         System.out.println("doGet()方法");
35     }
36 
37     @Override
38     public void destroy() {
39         System.out.println("destroy()方法");
40     }
41 }

// sum.jsp页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>请求跳转求和</title>
</head>
<body>
a + b = <%=request.getAttribute("sum")%>
</body>
</html>

// sum2.jsp页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>重定向跳转求和</title>
</head>
<body>
a + b = <%=application.getAttribute("sum2")%>
</body>
</html>

index.jsp page renderings display:

1. Method 1: PrintWriter object writing renderings:

2. Method 2: Request forwarding renderings:

3. Redirection renderings:

Idea creates a simple web project to analyze the difference between Servlet request forwarding and redirection

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