转发和重定向的对比

小咪咪 2022-06-07 12:08 190阅读 0赞

**转发和重定向的区别：**

1、  转发不会改变浏览器的地址栏，而重定向会

2、  转发是在服务器端执行跳转，重定向是在浏览器端执行跳转

3、  转发客户端只发一次请求，重定向整个过程会发两次请求

4、  转发可以传递数据，而重定向不可以

5、  转发只是进行域内跳转，重定向可以跳转到其他应用（如：www.baidu.com）

**转发：**

servletDemo1:

@WebServlet("/demo1")
    public class ServletDemo1 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	public ServletDemo1() {
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		/*转发*/
    		System.out.println("A:我要办事");
    		System.out.println("B:你的事我办不了，我可以找人给你办");
    		ServletContext application = this.getServletContext();
    		application.getRequestDispatcher("/demo2").forward(request, response);
    		System.out.println("事办完了");
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

servletDemo2:

@WebServlet("/demo2")
    public class ServletDemo2 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        public ServletDemo2() {
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		System.out.println("C:***我能帮你办***");
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

当在浏览器中访问demo1时，demo1将请求（由服务器端的servletContext域对象）转发给demo2，并且在转发前后浏览器地址栏不会发生变化。

![Center][]

![Center 1][]

由输出结果看出，在执行跳转后，程序还是回到demo1执行剩余的代码。

转发数据的共享：

更该上面程序的代码：

@WebServlet("/demo1")
    public class ServletDemo1 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	public ServletDemo1() {
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		/*转发*/
    		ServletContext application = this.getServletContext();//两个servlet共享域数据
    		application.setAttribute("name", "tom");
    		application.getRequestDispatcher("/demo2").forward(request, response);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

@WebServlet("/demo2")
    public class ServletDemo2 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        public ServletDemo2() {
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		ServletContext application = this.getServletContext();//两个servlet共享域数据
    		String name = (String)application.getAttribute("name");
    		System.out.println(name);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

![Center 2][]

因为这是一次访问过程，servletContext是域对象，所以进行跳转后，在demo2中可以得到demo1中的数据,因此转发可以共享数据。

**重定向：**

这是servletDemo7

@WebServlet("/demo7")
    public class ServletDemo7 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
        public ServletDemo7() {
            super();
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//请求重定向
    		System.out.println("A:我要借钱");
    		System.out.println("B:我没钱，但我可以告诉你谁有");
    		response.sendRedirect("/day09_response/demo8");		 System.out.println("事办完了");
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

这是servletDemo8

WebServlet("/demo8")
    public class ServletDemo8 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        public ServletDemo8() {
            super();
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		System.out.println("C:我借给你...");
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

当在浏览器端访问servletDemo7时，浏览器的地址

![Center 3][]

访问结束后，浏览器的地址

![Center 4][]

由此可以看出，进行重定向改变了浏览器的地址栏信息。

执行结果:

![Center 5][]

由执行结果看出,在servletDemo7进行重定向之前，会把其中的所有代码执行完之后，在进行重定向操作。重定向时将新的url地址发给浏览器，再由浏览器进行重新访问，因此会改变浏览器地址栏的信息。所以重定向会发送两次访问请求。

若上面代码为：response.sendRedirect(“http://www.baidu.com”);会跳转到百度

![Center 6][]

用一张图来表示上述的过程：

![Center 7][]

好了，就写这么多，排版不太好看，各位大佬凑合看看！

[Center]: /images/20220607/17da59545489440caafa3df3d66118a5.png
[Center 1]: /images/20220607/1018a5f4a7d64b18b883a6e9bc2606a0.png
[Center 2]: /images/20220607/d6b0ad57f5c04469890dd5b8e5f79c14.png
[Center 3]: /images/20220607/4b09f8020fd544ab8bbb1cdb9e71dd0e.png
[Center 4]: /images/20220607/212b4bb6dfd64d8aa5e9b72f835919f3.png
[Center 5]: /images/20220607/b70c1a9367fc426d950c21754fc12469.png
[Center 6]: /images/20220607/c6c569e547a34245a892d3f7c7c6bcaa.png
[Center 7]: /images/20220607/0dd5b508a2ca4dd68eccd44a584d17f3.png