請求的轉發和重定向：
1）本質區別：請求的轉發只發出一次請求，而重定向則發出來兩次請求。
具體：
①請求的轉發：地址欄是初次發出請求的地址
請求的重定向：地址欄不再是初次發出的請求地址，地址欄為最后響應的那個地址
②請求轉發：在最終的Servlet中，request對象和中轉的那個request是同一個對象
請求的重定向：在最終的Servlet中，request對象和中轉的那個request不是同一個對象
(3)請求的轉發：只能轉發給當前WEB應用的資源
請求的重定向：可以重定向到任何資源。
④請求轉發：/ 代表的是當前WEB應用的根目錄
請求重定向：/ 代表的是當前WEB站點的根目錄
JSP
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<a href="ForwardServlet">ForwardServlet</a>
<br>
<a href="RedirectServlet">RedirectServlet</a>
</body>
</html>
Servlet
public class ForwardServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("ForwardServlet's doGet");
/**
* 請求的轉發
* 1.調用HttpServletRequest的getRequestDispatcher()方法獲取RequestDispatcher對象
* 調用getRequestDispatcher()需要傳入要轉發的地址
*/
String path = "/TestServlet";
RequestDispatcher requestDispatcher = request.getRequestDispatcher(path);
/**
* 2.調用HttpServletRequest的forward(request,response)進行請求的轉發
*/
requestDispatcher.forward(request,response);
}
public class TestServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("TestServlet's doGet");
}
}
@WebServlet(name = "RedirectServlet")
public class RedirectServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("RedirectServlet's doGet");
//執行請求的重定向，直接調用response，sendRedirect(path)方法
//path為要重定向的地址
String path = "TestServlet";
response.sendRedirect(path);
}
}