@Overrideprotected void initFilterBean() throws ServletException {synchronized (this.delegateMonitor) {if (this.delegate == null) {// If no target bean name specified, use filter name.if (this.targetBeanName == null) {this.targetBeanName = getFilterName();}// Fetch Spring root application context and initialize the delegate early,// if possible. If the root application context will be started after this// filter proxy, we'll have to resort to lazy initialization.WebApplicationContext wac = findWebApplicationContext();if (wac != null) {this.delegate = initDelegate(wac);}}}}

    /*** Initialize the Filter delegate, defined as bean the given Spring* application context.* <p>The default implementation fetches the bean from the application context* and calls the standard {@code Filter.init} method on it, passing* in the FilterConfig of this Filter proxy.* @param wac the root application context* @return the initialized delegate Filter* @throws ServletException if thrown by the Filter* @see #getTargetBeanName()* @see #isTargetFilterLifecycle()* @see #getFilterConfig()* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)*/protected Filter initDelegate(WebApplicationContext wac) throws ServletException {Filter delegate = wac.getBean(getTargetBeanName(), Filter.class);if (isTargetFilterLifecycle()) {delegate.init(getFilterConfig());}return delegate;}

    @Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)throws ServletException, IOException {// 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);}

    /*** Actually invoke the delegate Filter with the given request and response.* @param delegate the delegate Filter* @param request the current HTTP request* @param response the current HTTP response* @param filterChain the current FilterChain* @throws ServletException if thrown by the Filter* @throws IOException if thrown by the Filter*/protected void invokeDelegate(Filter delegate, ServletRequest request, ServletResponse response, FilterChain filterChain)throws ServletException, IOException {delegate.doFilter(request, response, filterChain);}

    /*** Destroy the Filter delegate.* Default implementation simply calls {@code Filter.destroy} on it.* @param delegate the Filter delegate (never {@code null})* @see #isTargetFilterLifecycle()* @see javax.servlet.Filter#destroy()*/protected void destroyDelegate(Filter delegate) {if (isTargetFilterLifecycle()) {delegate.destroy();}}