MemcachedSessionFilter.java

package com.hehenian.common.memcache;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.lang.RandomStringUtils;
import org.apache.commons.lang.StringUtils;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.filter.OncePerRequestFilter;

public class MemcachedSessionFilter extends OncePerRequestFilter {

	private HttpSessionManager sessionManager;
	private String sessionSuffix;

	private String mixSessionId(String sessionIdInCookie, HttpServletRequest req) {
		if (StringUtils.isEmpty(sessionIdInCookie)) {
			return null;
		}
		// sessionIdInCookie += req.getRemoteAddr();
		// return DigestUtils.md5Hex(sessionIdInCookie);
		// ���ܰ�ip��ַ����Ϊ��Щ������˫�߻��߶��ߵģ�ÿ�������ip����һ��
		return sessionIdInCookie;
	}

    @Override
	protected void doFilterInternal(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
			throws ServletException, IOException {
		String sessionKey = sessionManager.getSessionKey();
		String cookiePath = sessionManager.getCookiePath();
		int sessionTimeout = sessionManager.getSessionTimeout();
		// ��cookie��ȡ��sessionId
		Cookie cookies[] = req.getCookies();
		String sessionIdInCookie = null;
		boolean sessionFromCookie = true;
		if (cookies != null && cookies.length > 0) {
			for (int i = 0; i < cookies.length; i++) {
				if (cookies[i].getName().equals(sessionKey)) {
					sessionIdInCookie = cookies[i].getValue();
				}
			}
		}
		if (sessionIdInCookie == null) {
			sessionIdInCookie = parseSessionIdFromUri(req);
			sessionFromCookie = false;
		}
		String sessionId = mixSessionId(sessionIdInCookie, req);
		HttpSession session = sessionManager.getSession(sessionId);
		if (session == null) {
			String newSessionId = RandomStringUtils.randomAlphanumeric(20);
			// ����sessionId
			sessionId = mixSessionId(newSessionId, req);
			session = sessionManager.newSession(sessionId);
			Cookie sessionCookie = new Cookie(sessionKey, newSessionId);
			sessionCookie.setPath(cookiePath);
            sessionCookie.setDomain(sessionManager.getCookieDomain());
			res.addCookie(sessionCookie);
		}
		session.setMaxInactiveInterval(sessionTimeout * 60);

		req = new HttpSessionRequestWrapper(req, session);
		res = new HttpSessionResponseWrapper(res, session, sessionManager, sessionFromCookie);
		chain.doFilter(req, res);
		sessionManager.updateSession(session);
	}

	@Override
	protected void initFilterBean() throws ServletException {
		WebApplicationContext spring = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
		sessionManager = (HttpSessionManager) spring.getBean("sessionManager");
		sessionSuffix = ";" + sessionManager.getSessionKey() + "=";
	}

	@Override
	public void destroy() {
		sessionManager = null;
	}

	private String parseSessionIdFromUri(HttpServletRequest request) {
		String sessionId = null;
		String uri = request.getRequestURI();
		int p = uri.indexOf(sessionSuffix);
		if (p >= 0) {
			int suffixLength = sessionSuffix.length();
			int tail = uri.indexOf(';', p + suffixLength);
			if (tail > 0)
				sessionId = uri.substring(p + suffixLength, tail);
			else
				sessionId = uri.substring(p + suffixLength);
		}
		return sessionId;
	}
}