基于redis的session共享实现

项目上线，闲来无事，把项目里用到的session共享贴出来，因为有多个项目要用到这个功能，所以这个部分功能独立出来了。总得来说，就是自己写了一个拦截器，在拦截器里面把session放进了redis里面，从而实现了session共享。

首先贴出web.xml的配置,和普通拦截器的配置一样：

<filter>    <filter-name>sessionFilter</filter-name>    <filter-class>com.dnkx.web.filter.SessionFilter</filter-class>  </filter>  <filter-mapping>    <filter-name>sessionFilter</filter-name>    <url-pattern>/*</url-pattern>  </filter-mapping>  <!-- session过期时间 -->  <session-config>    <session-timeout>30</session-timeout>  </session-config>

然后是sessionFilter：

public class SessionFilter extends HttpServlet implements Filter {    /** *  */private static final long serialVersionUID = -5723213015901607291L;@Override    public void init(FilterConfig filterConfig) throws ServletException {    }    @Override    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {        HttpServletRequest request = (HttpServletRequest) servletRequest;        HttpServletResponse response = (HttpServletResponse) servletResponse;        request.setAttribute("hostname", InetAddress.getLocalHost().getHostName());        filterChain.doFilter(new HttpServletRequestWrapper(request, response),                servletResponse);    }}

上面两段代码都是基础，没什么好解释的，下面贴出关键的HttpServletRequestWrapper类：

public class HttpServletRequestWrapper extends        javax.servlet.http.HttpServletRequestWrapper {    private static final String cookieId = "csid";    static String sessionHoldKey = "session_hold_key";    private String sessionId;    public HttpServletRequestWrapper(HttpServletRequest request, HttpServletResponse response) {        super(request);        sessionIdManage(request, response);    }    @SuppressWarnings({ "rawtypes", "unchecked" })private void sessionIdManage(HttpServletRequest request, HttpServletResponse response) {        Cookie[] cookies = request.getCookies();        if (cookies == null ) {           // logger.warn("request.getCookies() returns null,I didn't see it before");        } else {            for (int i = 0; i < cookies.length; i++) {                Cookie sCookie = cookies[i];                if (sCookie.getName().equals(cookieId)) {                    sessionId = sCookie.getValue();                }            }        }        if (sessionId == null || sessionId.length() == 0) {            sessionIdCreate(response);        }        HashOperations hashOps = WebComponentFactory.getSessionRedisTemplate().opsForHash();        Long lastAccessedTime = (Long) hashOps.get(sessionId, sessionHoldKey);        long maxInactiveInterval = request.getSession().getMaxInactiveInterval() * 1000;        if (lastAccessedTime == null || maxInactiveInterval > 0 && System.currentTimeMillis() - lastAccessedTime > maxInactiveInterval) {            sessionIdCreate(response);        }        hashOps.put(sessionId, sessionHoldKey, System.currentTimeMillis());        WebComponentFactory.getSessionRedisTemplate().expire(sessionId,3, TimeUnit.DAYS);    }    private void sessionIdCreate(HttpServletResponse response) {        sessionId = java.util.UUID.randomUUID().toString();        Cookie mycookies = new Cookie(cookieId, sessionId);        mycookies.setPath("/");        response.addCookie(mycookies);    }    public HttpSession getSession(boolean create) {        return new HttpSessionSidWrapper(this.sessionId, super.getSession(create));    }    public HttpSession getSession() {        return new HttpSessionSidWrapper(this.sessionId, super.getSession());    }}

上面这段代码是session共享的关键部分，这里需要了解cookie和session的机制，这里是用一个自己的cookie存了自己生成的sessionId返回给客户端，每次请求在根据cookie的值来做session的操作，sessionId是存在redis里面的，根据session做redis的get,set等操作，代码也很容易看懂。

完整源代码下载地址