servlet请求转发

请求转发时会共享request变量，但请求跳转时不共享该变量。
通过request.sendRedirect()实现重定向。
通过request.getRequestDispatcher().forward()实现请求转发。
通过request.getRequestDispatcher().include()实现请求包含。
请求重定向测试代码如下：

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        String url = request.getRequestURL().toString();
        
        System.out.println("=============================");
        System.out.println(url);
    
        String uname = request.getParameter("login");
        System.out.println("----------->"+uname);
        if(uname.equals("baidu")){
            response.sendRedirect("http://www.baidu.com");
        }else{
            response.sendRedirect("http://www.126.com");
        }
        
    }

通过输入内容判断如果输入baidu则跳转到百度首页，否则跳转到126首页。
转发测试代码如下：

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        String URL = this.getServletContext().getInitParameter("url");
        String Redurl = request.getParameter("url");
        System.out.println("--->"+ Redurl);
        System.out.println("------------->"+ URL);
        PrintWriter out = response.getWriter();
        
        
        if(Redurl.equals("baidu")){
            //response.sendRedirect("http://www.baidu.com");
            request.getRequestDispatcher("/success.html").forward(request, response);
        }else{
            //response.sendRedirect("http://www.126.com");
            request.getRequestDispatcher("/false.html").forward(request, response);
        }
out.print(this.getClass());
        out.println(", using the GET method");
        out.println("please url:"+ URL);
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

运行结果

通过request.getRequestDispatcher().include()实现转发包含，将指定页加到本页。

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        String URL = this.getServletContext().getInitParameter("url");
        String Redurl = request.getParameter("url");
        System.out.println("--->"+ Redurl);
        System.out.println("------------->"+ URL);
        PrintWriter out = response.getWriter();
        
        
        if(Redurl.equals("baidu")){
            //response.sendRedirect("http://www.baidu.com");
            //request.getRequestDispatcher("/success.html").forward(request, response);
            request.getRequestDispatcher("/success.html").include(request, response);
        }else{
            //response.sendRedirect("http://www.126.com");
            //request.getRequestDispatcher("/false.html").forward(request, response);
            request.getRequestDispatcher("/false.html").include(request, response);
        }
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("please url:"+ URL);
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

运行结果如图：

运行结果