URL重写技术_长url转短url

URL重写是指服务器程序对接收的URL请求重新写成网站可以处理的另一个URL的过程。URL重写技术是实现动态网站会话跟踪的重要保障。在实际应用中，当不能确定客户端浏览器是否支持Cookie的情况下，使用URL重写技术可以对请求的URL地址追加会话标识，从而实现用户的会话跟踪功能。URL重写实现会话跟踪，要保证每个页面都必须使用Servlet或JSP动态页面。因为附加在URL上的SessionID是动态产生的，所以对于静态页面的跳转，URL重写机制无能为力。
可以通过HttpServletResponse 的encodeURL(方法和encodeRedirectURL()方法实现URL重写，其中，encodeRedirectURL(方法主要对使用sendRedirect()方法的URL进行重写。URL重写方法根据请求信息中是否包含Set-Cookie 请求头来决定是否进行URL重写。若包含了该请求头，将URL原样输出;若不包含，则将会话标识JSESSIONID重写到URL中。URL重写示例代码如下:
//对重定向的URL进行重写
String encodeURL = response. encodeRedirectURL(“toRedi rectServlet”);
response. sendRedirect (encodeURL);
然后禁用浏览器Cookie；

useSession.jsp代码：

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>useSession.jsp</title>
</head>
  <body>
   <form action="<%=response.encodeURL("sendMyName")%>" method="post">
    	<table>
    		<tr>
    			<td>用户名：</td>
    			<td><input type="text" name="user"/></td>
    		</tr>
    		<tr>
    			<td><input type="submit" value="提交"/></td>
    		</tr>
    	</table>	
    </form>
  </body>
</html>

UseSessionServlet.java代码:

package servlet;

import java.io.*;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
@WebServlet(name = "useSession", urlPatterns = { "/sendMyName" })
public class UseSessionServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	public void init(ServletConfig config) throws ServletException {
		super.init(config);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		request.setCharacterEncoding("UTF-8");
		String name = request.getParameter("user");
		if (null == name || name.trim().length() == 0) {
			response.sendRedirect(response.encodeRedirectURL("useSession.jsp"));
		} else {
			HttpSession session = request.getSession(true);
			session.setAttribute("myName", name);
			out.println("<htm><body>");
			out.println("您请求的servlet对象是：" + getServletName());
			out.println("<br>您的会话ID是：" + session.getId());
			out.println("<br>请单击请求另一个servlet：");
			out.println("<br><a href=" + response.encodeURL("showMyName") + ">请求另一个servlet</a>");
			out.println("</body></htm>");
		}
	}

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

ShowNameServlet代码：

package servlet;

import java.io.*;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
@WebServlet(name = "showMyName", urlPatterns = { "/showMyName" })
public class ShowNameServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		HttpSession session = request.getSession(true);
		String name = (String)session.getAttribute("myName");
		if (null == name || name.trim().length() == 0) {
			response.sendRedirect(response.encodeRedirectURL("useSession.jsp"));
		}else{
			out.println("<htm><body>");
			out.println("您请求的servlet对象是：" + getServletName());
			out.println("<br>您的会话ID是：" + session.getId());
			out.println("<br>您的会话中存储的用户名是：" + name);
			out.println("<br><a href=" + response.encodeRedirectURL("useSession.jsp") + ">重新登录</a>");
			out.println("</body></htm>");
		}
	}

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