http://liuluo129.iteye.com/blog/1965268
图来自上面连接
http://blog.csdn.net/geloin/article/details/7441330
整理于上面
Spring的web包中中有很多过滤器,这些过滤器位于org.springframework.web.filter并且理所当然地实现了javax.servlet.Filter,不过实现的方式有以下几类:
(1) 直接实现Filter,这一类过滤器只有CompositeFilter;
(2) 继承抽象类GenericFilterBean,该类实现了javax.servlet.Filter,这一类的过滤器只有一个,即DelegatingFilterProxy;
(3) 继承抽象类OncePerRequestFilter,该类为GenericFilterBean的直接子类,这一类过滤器包括CharacterEncodingFilter、HiddenHttpMethodFilter、HttpPutFormContentFilter、RequestContextFilter和ShallowEtagHeaderFilter;
(4) 继承抽象类AbstractRequestLoggingFilter,该类为OncePerRequestFilter的直接子类,这一类过滤器包括CommonsRequestLoggingFilter、Log4jNestedDiagnosticContextFilter和ServletContextRequestLoggingFilter。
本文要讲述的,即是GenericFilterBean、OncePerRequestFilter和AbstractRequestLoggingFilter。
GenericFilterBean
抽象类GenericFilterBean实现了javax.servlet.Filter、org.springframework.beans.factory.BeanNameAware、org.springframework.context.EnvironmentAware、org.springframework.web.context.ServletContextAware、org.springframework.beans.factory.InitializingBean和org.springframework.beans.factory.DisposableBean五个接口,作用如下:
(1) Filter,实现过滤器;
(2) BeanNameAware,实现该接口的setBeanName方法,便于Bean管理器生成Bean;
(3) EnvironmentAware,实现该接口的setEnvironment方法,指明该Bean运行的环境;
(4) ServletContextAware,实现该接口的setServletContextAware方法,指明上下文;
(5) InitializingBean,实现该接口的afterPropertiesSet方法,指明设置属性生的操作;
(6) DisposableBean,实现该接口的destroy方法,用于回收资源。
GenericFilterBean的工作流程是:init-doFilter-destory,其中的init和destory在该类中实现,doFilter在具体实现类中实现。init的代码如下:
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- public final void init(FilterConfig filterConfig) throws ServletException {
- Assert.notNull(filterConfig, "FilterConfig must not be null");
- if (logger.isDebugEnabled()) {
- logger.debug("Initializing filter '" + filterConfig.getFilterName() + "'");
- }
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- this.filterConfig = filterConfig;
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- try {
- PropertyValues pvs = new FilterConfigPropertyValues(filterConfig, this.requiredProperties);
- BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
- ResourceLoader resourceLoader = new ServletContextResourceLoader(filterConfig.getServletContext());
- bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
- initBeanWrapper(bw);
- bw.setPropertyValues(pvs, true);
- }
- catch (BeansException ex) {
- String msg = "Failed to set bean properties on filter '" +
- filterConfig.getFilterName() + "': " + ex.getMessage();
- logger.error(msg, ex);
- throw new NestedServletException(msg, ex);
- }
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- initFilterBean();
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- if (logger.isDebugEnabled()) {
- logger.debug("Filter '" + filterConfig.getFilterName() + "' configured successfully");
- }
- }
该方法来自于javax.servlet.Filter,即过滤器的初始化,它的主要工作集中于以下几行代码:
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- PropertyValues pvs = new FilterConfigPropertyValues(filterConfig, this.requiredProperties);
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- BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
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- ResourceLoader resourceLoader = new ServletContextResourceLoader(filterConfig.getServletContext());
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- bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
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- initBeanWrapper(bw);
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- bw.setPropertyValues(pvs, true);
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- initFilterBean();
其中initFilterBean方法在两个位置起作用,一处是上文所述的init方法,另一处是afterPropertiesSet方法,在调用该方法前,需要保证用于Filter的所有的bean都已被设置,该方法由子类实现。
GenericFilterBean中包含一个内部私有类FilterConfigPropertyValues,主要用于将web.xml中定义的init-param的值取出。
OncePerRequestFilter
抽象类oncePerRequestFilter继承自GenericFilterBean,它保留了GenericFilterBean中的所有方法并对之进行了扩展,在oncePerRequestFilter中的主要方法是doFilter,代码如下:
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- public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
- throws ServletException, IOException {
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- if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
- throw new ServletException("OncePerRequestFilter just supports HTTP requests");
- }
- HttpServletRequest httpRequest = (HttpServletRequest) request;
- HttpServletResponse httpResponse = (HttpServletResponse) response;
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- String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();
- if (request.getAttribute(alreadyFilteredAttributeName) != null || shouldNotFilter(httpRequest)) {
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- filterChain.doFilter(request, response);
- }
- else {
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- request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);
- try {
- doFilterInternal(httpRequest, httpResponse, filterChain);
- }
- finally {
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- request.removeAttribute(alreadyFilteredAttributeName);
- }
- }
- }
在doFilter方法中,doFilterInternal方法由子类实现,主要作用是规定过滤的具体方法。
AbstractRequestLoggingFilter
AbstractRequestLoggingFilter继承了OncePerRequestFilter并实现了其doFilterInternal方法,该方法代码如下:
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原文链接:https://blog.csdn.net/liangxw1/article/details/51095484
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发表于 2021-06-26 16:17:39
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