URL重写实现会话跟踪

来源：互联网发布：淘宝充流量如何退款编辑：程序博客网时间：2024/05/16 17:33

servlet创建的所有链接的重定向都必须将会话ID编码为URL的一部分。在服务器指定的URL编码的方法中，最可能的一种是给URL加入一些参数或者附加的路径信息。

　为了说明URL Rewriting技术，我们编写sevlet实现访问记数。下面代码显示了CounterRewriteServlet的源程序，它使用URL Rewriting技术来在HTTP请求之间维护会话信息。

package sample;
import javax.servlet.*;
import javax.servlet.http.*;
public class CounterRewrite extends HttpServlet
{
static final String COUNTER_KEY = "CounterRewrite.count";
public void doGet(HttpServletRequest req,
HttpServletResponse resp)
throws ServletException, java.io.IOException
{
resp.setContentType("text/html");
java.io.PrintWriter out = resp.getWriter();
HttpSession session = req.getSession(true);
int count = 1;
Integer i = (Integer) session.getValue(COUNTER_KEY);
if (i != null) {
count = i.intValue() + 1;
}
session.putValue(COUNTER_KEY, new Integer(count));
out.println("<html>");
out.println("<head>");
out.println("<title>Session Counter " +"with URL rewriting</title>");
out.println("</head>");
out.println("<body>");
out.println("Your session ID is <b>" +session.getId());
out.println("</b> and you have hit this page <b>" +count +
"</b> time(s) during this browser session");
String url = req.getRequestURI()+ ";" + SESSION_KEY +session.getId();
out.println("<form method=POST action=\"" +resp.encodeUrl(url) + "\">");
out.println("<input type=submit " +"value=\"Hit page again\">");
out.println("</form>");
out.println("</body>");
out.println("</html>");
out.flush();
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, java.io.IOException
{
doGet(req, resp);
}
}

请注意，encodeURL方法被用来修改URL，使URL包含会话ID；encodeRedirectURL被用来重定向页面