Insight spring-session 配置（整合方式）

servlet、Spring整合方式-
org.springframework.web.context.support.WebApplicationContextUtils#getWebApplicationContext(javax.servlet.ServletContext)

Filter實現類 org.springframework.web.filter.DelegatingFilterProxySpring-Session實現類  springSessionRepositoryFilter

/**
 * 此處的 delegateToUse就是分散式httpsession的bean
 * doFilter過程中進行初始化check    （漂亮的程式碼隨處可見啊）
 * 然後將分散式httpsession加入請求的filterChain, 達到httpsession代理的目的
 **/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) {
    // Lazily initialize the delegate if necessary.
    Filter delegateToUse = this.delegate;
    if (delegateToUse == null) {
        synchronized (this.delegateMonitor) {
            if (this.delegate == null) {
                WebApplicationContext wac = findWebApplicationContext();
                if (wac == null) {
                    throw new IllegalStateException("No WebApplicationContext found: " + "no ContextLoaderListener or DispatcherServlet registered?");
                }
                this.delegate = initDelegate(wac);
            }
            delegateToUse = this.delegate;
        }
    }
    // Let the delegate perform the actual doFilter operation.
    invokeDelegate(delegateToUse, request, response, filterChain);
}

/**
 * web.xml 配置的httpsession bean 來自此處
 * 構造spring-session filter 需要真正的儲存物件 redis/jdbc/gemfire
 **/
@Bean
public  SessionRepositoryFilter<? extends ExpiringSession> springSessionRepositoryFilter(SessionRepository sessionRepository) {
    SessionRepositoryFilter sessionRepositoryFilter = new SessionRepositoryFilter(sessionRepository);
    sessionRepositoryFilter.setServletContext(this.servletContext);
    sessionRepositoryFilter.setHttpSessionStrategy(this.httpSessionStrategy);
    return sessionRepositoryFilter;
}