Spring Session 学习记录1

先写些废话

　　新公司项目是有用到redis,之前老公司使用的缓存框架是ehcache.我redis并不熟悉.看过介绍以后知道是个nosql..既然是个数据库,那我想操作方法和jdbc操作关系数据库应该差不多吧..百度了一些例子以后发现确实差不多...比如注入一个spring的template以后使用template就行了. 比如:

　　很好理解,使用也蛮简单..就像jdbcTemplate...

　　一次偶然的调试,我发现了一个有趣的地方(公司用的是自己的框架,封装了springboot...所以启动默认配置了什么bean,很难看出来...)...

我记得session在tomcat启动服务器的时候好像是XXXSessionFacade..这里却是和Redis相关的一个实现类..然后向这个session存进去的东西再redis里也可以找到.

这说明这个session数据存取都是向redis去操作的.

看来一下maven的POM文件发现公司的项目依赖于srping-session-data-redis这个框架.

Spring整合SpringSession

实验了一下,发现其实spring只要额外配置2个bean就可以集成springsession了.

    <context:annotation-config />
     <bean class="org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration">
    </bean> 

    <bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory">
        <property name="hostName" value="10.86.87.173" />
        <property name="password" value="mesRedis+)" />
    </bean>

稍微研究了下发现JedisConnectionFactory这个bean就是配置了Spring怎么通过jedis去连接redis服务器.

RedisHttpSessionConfiguration这个bean是真正和session相关的,它本身类上有注解@Configuration和@EnableScheduling.

@Configuration配合它方法上的@Bean可以配置一些其他的bean,比如SessionRepositoryFilter 就配置了一个bean,对应web.xmlXML里配置的那个filter...

@EnableScheduling这个注解我没用过,估计是要定时做一些事情,比如session过期了要去redis删除数据吧(但是redis好像也有超时删除数据的功能,为啥还要这么做呢..redis和Springsession都是第一次用,不太了解)..

除了上面2个bean,只要在web.xml里配置一个filter就行了.

     <filter>
         <filter-name>springSessionRepositoryFilter</filter-name>
         <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
     </filter>
     <filter-mapping>
         <filter-name>springSessionRepositoryFilter</filter-name>
         <url-pattern>/*</url-pattern>
     </filter-mapping>

原理

因为第一次用,很多代码都没看过,所以不一定对.我觉得原理是这样的:

1.RedisHttpSessionConfiguration里会配置一个filter

    @Bean
    public <S extends ExpiringSession> SessionRepositoryFilter<? extends ExpiringSession> springSessionRepositoryFilter(SessionRepository<S> sessionRepository, ServletContext servletContext) {
        SessionRepositoryFilter<S> sessionRepositoryFilter = new SessionRepositoryFilter<S>(sessionRepository);
        sessionRepositoryFilter.setServletContext(servletContext);
        if(httpSessionStrategy != null) {
            sessionRepositoryFilter.setHttpSessionStrategy(httpSessionStrategy);
        }
        return sessionRepositoryFilter;
    }

注入一个sessionRepository.这个repository其实就是redis的repository.只是哪里生成的我并不知道...

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        request.setAttribute(SESSION_REPOSITORY_ATTR, sessionRepository);

        SessionRepositoryRequestWrapper wrappedRequest = new SessionRepositoryRequestWrapper(request, response, servletContext);
        SessionRepositoryResponseWrapper wrappedResponse = new SessionRepositoryResponseWrapper(wrappedRequest,response);

        HttpServletRequest strategyRequest = httpSessionStrategy.wrapRequest(wrappedRequest, wrappedResponse);
        HttpServletResponse strategyResponse = httpSessionStrategy.wrapResponse(wrappedRequest, wrappedResponse);

        try {
            filterChain.doFilter(strategyRequest, strategyResponse);
        } finally {
            wrappedRequest.commitSession();
        }
    }

这个filter会把request和response外面包装一层,就是装饰着模式.当调用request的getSession的时候

        @Override
        public HttpSession getSession(boolean create) {
            HttpSessionWrapper currentSession = getCurrentSession();
            if(currentSession != null) {
                return currentSession;
            }
            String requestedSessionId = getRequestedSessionId();
            if(requestedSessionId != null) {
                S session = sessionRepository.getSession(requestedSessionId);
                if(session != null) {
                    this.requestedSessionIdValid = true;
                    currentSession = new HttpSessionWrapper(session, getServletContext());
                    currentSession.setNew(false);
                    setCurrentSession(currentSession);
                    return currentSession;
                }
            }
            if(!create) {
                return null;
            }
            S session = sessionRepository.createSession();
            currentSession = new HttpSessionWrapper(session, getServletContext());
            setCurrentSession(currentSession);
            return currentSession;
        }

其实是从sessionRepository里去拿session的.所以我们使用的HttpSession的实现类应该是 HttpSessionWrapper 里面包裹着 RedisSession.

     private RedisSession getSession(String id, boolean allowExpired) {
         Map<Object, Object> entries = getSessionBoundHashOperations(id).entries();
         if(entries.isEmpty()) {
             return null;
         }
         MapSession loaded = new MapSession();
         loaded.setId(id);
         for(Map.Entry<Object,Object> entry : entries.entrySet()) {
             String key = (String) entry.getKey();
             if(CREATION_TIME_ATTR.equals(key)) {
                 loaded.setCreationTime((Long) entry.getValue());
             } else if(MAX_INACTIVE_ATTR.equals(key)) {
                 loaded.setMaxInactiveIntervalInSeconds((Integer) entry.getValue());
             } else if(LAST_ACCESSED_ATTR.equals(key)) {
                 loaded.setLastAccessedTime((Long) entry.getValue());
             } else if(key.startsWith(SESSION_ATTR_PREFIX)) {
                 loaded.setAttribute(key.substring(SESSION_ATTR_PREFIX.length()), entry.getValue());
             }
         }
         if(!allowExpired && loaded.isExpired()) {
             return null;
         }
         RedisSession result = new RedisSession(loaded);
         result.originalLastAccessTime = loaded.getLastAccessedTime() + TimeUnit.SECONDS.toMillis(loaded.getMaxInactiveIntervalInSeconds());
         result.setLastAccessedTime(System.currentTimeMillis());
         return result;
     }

         @Override
         public HttpSession getSession(boolean create) {
             HttpSessionWrapper currentSession = getCurrentSession();
             if(currentSession != null) {
                 return currentSession;
             }
             String requestedSessionId = getRequestedSessionId();
             if(requestedSessionId != null) {
                 S session = sessionRepository.getSession(requestedSessionId);
                 if(session != null) {
                     this.requestedSessionIdValid = true;
                     currentSession = new HttpSessionWrapper(session, getServletContext());
                     currentSession.setNew(false);
                     setCurrentSession(currentSession);
                     return currentSession;
                 }
             }
             if(!create) {
                 return null;
             }
             S session = sessionRepository.createSession();
             currentSession = new HttpSessionWrapper(session, getServletContext());
             setCurrentSession(currentSession);
             return currentSession;
         }