idea创建简单web项目分析Servlet的请求转发与重定向的区别
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需求说明：
// index.jsp页面 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加法运算</title> 9 </head> 10 <body> 11 <%--action: 表示访问的servlet路径--%> 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 // 方式一：PrintWriter对象写入 27 // response.getWriter().print(sum); 28 // 方式二：请求转发 29 // request.getRequestDispatcher("sum.jsp").forward(request, response); 30 // 方式三：重定向 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页面效果图展示：
1. 方式一：PrintWriter对象写入效果图：
2. 方式二：请求转发效果图：
3. 重定向效果图：
