【下载文档:  jsp跳转getRequestDispatcher()和sendRedirect()的区别.txt 】

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jsp跳转getRequestDispatcher()和sendRedirect()的区别
1.request.getRequestDispatcher()是请求转发，前后页面共享一个request ;response.sendRedirect()是重新定向，前后页面不是一个request。
2.RequestDispatcher.forward()是在服务器端运行;HttpServletResponse.sendRedirect()是通过向客户浏览器发送命令来完成.所以RequestDispatcher.forward()对于浏览器来说是“透明的”；而HttpServletResponse.sendRedirect()则不是。
3.ServletContext.getRequestDispatcher(String url)中的url只能使用绝对路径； 而ServletRequest.getRequestDispatcher(String url)中的url可以使用相对路径。因为ServletRequest具有相对路径的概念；而ServletContext对象无次概念。
RequestDispatcher对象从客户端获取请求request，并把它们传递给服务器上的servlet,html或jsp。它有两个方法:
1.void forward(ServletRequest request,ServletResponse response)
用来传递request的，可以一个Servlet接收request请求，另一个Servlet用这个request请 求来产生response。request传递的请求，response是客户端返回的信息。forward要在response到达客户端之前调用，也 就是 before response body output has been flushed。如果不是的话，它会报出异常。
2.void include(ServletRequest request,ServletResponse response)
用来记录保留request和response，以后不能再修改response里表示状态的信息。
如果需要把请求转移到另外一个Web App中的某个地址，可以按下面的做法：1. 获得另外一个Web App的ServletConext对象(currentServletContext.getContext(uripath)).
2. 调用ServletContext.getRequestDispatcher(String url)方法。
eg:ServletContext.getRequestDispatcher(“smserror.jsp”).forward(request,response);
代码实例：index.jsp：复制代码 代码如下:<%@ page language="java" import="java.util.*" pageEncoding="GBK"%><% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>My JSP 'index.jsp' starting page

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session.java：复制代码 代码如下:import java.io.IOException;import java.io.PrintWriter;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class session extends HttpServlet { /** * Constructor of the object. */ public session() { super(); } /** * Destruction of the servlet. */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } /** * The doPost method of the servlet. * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username = ""; String password = ""; username = request.getParameter("username"); password = request.getParameter("password"); HttpSession session = request.getSession(); session.setAttribute("username", username); session.setAttribute("password", password); request.setAttribute("name", username); request.setAttribute("pwd", password); RequestDispatcher dis = request.getRequestDispatcher("/getsession.jsp"); dis.forward(request, response); /* response.sendRedirect("http://localhost:8080/sessiontest/getsession.jsp"); */ //这个路径必须是这样写，而不能像上面的request.getRequestDispatcher那样使用相对路径 // 而且要是使用response.sendRedirect的话在下面的session.jsp中不能通过request.getAttribute来获取request对象 //因为前后使用的不是同一个request，但是session可以，因为session会一直存在直到用户关闭浏览器 } /** * Initialization of the servlet. * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here }}
getsession.jsp：
复制代码 代码如下:<%@ page language="java" import="java.util.*" pageEncoding="GBK"%><% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>My JSP 'getsession.jsp' starting page <% out.print(""); String username = (String)session.getAttribute("username"); String password = (String)session.getAttribute("password"); String name = (String)request.getAttribute("name"); String pwd = (String)request.getAttribute("pwd"); out.println("username " + username + " password " +password); //如果上面是使用response.sendRedirect的话就不能获取到name和pwd out.println("name " + name + "pwd "+ pwd); %>