使用Filter访问Session信息

import Javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

public class SessionFilter implements Filter {

private FilterConfig config;

/** Creates new SessionFilter */

public SessionFilter() {

}

public void init(FilterConfig filterConfig) throws ServletException {

System.out.println("Instance created of " + getClass().getName());

this.config = filterConfig;

}

public void doFilter(ServletRequest request, ServletResponse response,

FilterChain chain) throws java.io.IOException, ServletException {

HttpSession session = ((HttpServletRequest) request).getSession();

ServletContext context = config.getServletContext();

/*

* use the ServletContext.log method to log filter messages

*/

context.log("doFilter called in: " + config.getFilterName() + " on "

+ (new java.util.Date()));

// log the session ID

context.log("session ID: " + session.getId());

// Find out whether the logged-in session attribute is set

String logged = (String) session.getAttribute("logged-in");

if (logged == null)

session.setAttribute("logged-in", "no");

//log a message about the log-in status

context.log("log-in status: "

+ (String) session.getAttribute("logged-in"));

context.log("");

chain.doFilter(request, response);

}

public void destroy() {

/*

* called before the Filter instance is removed from service by the web

* container

*/

}

}

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