java过滤器

过滤器目标描述过滤器理解过滤器生命周期实现简单的过滤器过滤器简介过滤器是向Web应用程序的请求和响应处理添加功能的Web服务组件过滤器的工作原理：Web资源用户发送请求过滤器将用户的请求发送至Web资源资源将响应发送至过滤器过滤器将Web资源的响应发送给用户用户过滤器过滤器生命周期过滤器生命周期的各个阶段：实例化初始化过滤销毁Filter接口过滤器是一个对象，它根据用户的请求和资源的响应进行过滤Filter接口包含以下方法：Filter接口init()doFilter()destroy()过滤器链FilterChain接口用于调用过滤器链中的一系列过滤器用户过滤器1过滤器2过滤器3Web资源过滤器链FilterConfig在初始化过程中，容器使用FilterConfig将信息传递给过滤器FilterConfig接口包含以下方法：getFilterName()getInitParameter()getInitParameterNames()getServletContext()FilterConfig过滤器定义过滤器定义用于将过滤器名称与部署描述符中的特定类关联filterfilter-nameFilterName/filter-namefilter-classClassName/filter-class/filter指定过滤器的名称指定类的名称过滤器映射使用filter-mapping元素可将过滤器映射至Web资源，如Servletfilter-mappingfilter-nameMyFilter/filter-nameurl-pattern/servletname/*/url-pattern/filter-mapping指定过滤器的名称指定Servlet的名称过滤器定义和映射定义和映射过滤器部署描述符中filter和filter-mapping元素的用法?xmlversion=1.0encoding=UTF-8?!DOCTYPEweb-appPUBLIC-//SunMicrosystems,Inc.//DTDWebApplication2.3//EN*/url-pattern/filter-mapping/web-app创建Servlet演示：示例1...out.println(headtitleLoggerServlet/title/head);out.println(bodybgcolor=\#ffffff\);out.println(“h1简单过滤器Servlet/h1);StringrequestedUri=(String)request.getAttribute(requestURI);out.println(“b请求的URI为:/b+requestedUri);out.println(/body);out.println(/html);...创建过滤器演示：示例2FilterConfig、doFilter()、init()和destroy()方法的用法publicclassLoggerFilterextendsHttpServletimplementsFilter{privateFilterConfigfilterConfig;publicvoidinit(FilterConfigfilterConfig)throwsServletException{this.filterConfig=filterConfig;}publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainfilterChain){longstartTime=System.currentTimeMillis();StringremoteAddress=request.getRemoteAddr();StringremoteHost=request.getRemoteHost();HttpServletRequestmyReq=(HttpServletRequest)request;StringreqURI=myReq.getRequestURI();System.out.println(reqURI);创建HTML文件演示：示例3htmlheadtitle新文档/title/headbodyh1欢迎使用第一个过滤器示例/h1ahref=‘/FilterModule/loggerservlet’单击此处查看过滤器的效果/a/body/html实现过滤器链－过滤器1演示：示例4publicclassSimpleFilterextendsHttpServletimplementsFilter{privateFilterConfigfilterConfig;publicvoidinit(FilterConfigfilterConfig)throwsServletException{this.filterConfig=filterConfig;}publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainfilterChain)try{filterConfig.getServletContext().log(inSimpleFilter);System.out.println(inSimpleFilter);filterChain.doFilter(request,response);filterConfig.getServletContext().log(GettingoutofSimpleFilter);System.out.println(GettingoutofSimpleFilter);}catch(ServletExceptionsx){．．．}演示：示例5实现过滤器链－过滤器2publicclassSimpleFilter2extendsHttpServletimplementsFilter{privateFilterConfigfilterConfig;．．．publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainfilterChain){try{filterConfig.getServletContext().log(inSimpleFilter2);System.out.println(inSimpleFilter2);filterChain.doFilter(request,response);filterConfig.getServletContext().log(GettingoutofSimpleFilter2);System.out.println(GettingoutofSimpleFilter2);}catch(ServletExceptionsx){．．．}．．．}实现过滤器链－web.xmlfilterfilter-namesimplefilter/filter-namefilter-classmyfilter.SimpleFilter/filter-class/filterfilter-mappingfilter-namesimplefilter/filter-nameurl-pattern/*/url-pattern/filter-mappingfilterfilter-namesimplefilter2/filter-namefilter-classmyfilter.SimpleFilter2/filter-class/filterfilter-mappingfilter-namesimplefilter2/filter-nameurl-pattern/*/url-pattern/filter-mapping实现过滤器链htmlhead/headbodyh1欢迎访问过滤器链演示程序!/h1/body/html创建一个html文件作为Web资源总结过滤器是Web服务组件过滤器可以访问客户端输入的请求和Web资源输出的响应过滤器定义用于将过滤器名称与特定的类关联在一起过滤器映射用于将过滤器映射至Web资源Filter接口包含各种方法，如init()、doFilter()和destroy()每次用户发送请求或Web资源发送响应时都会调用doFilter()方法FilterChain接口用于调用过滤器链中的下一个过滤器在初始化过程中，Servlet使用FilterConfig将信息传递给过滤器