dayjavaweb之过滤器课件so easy系列教程

SoEasy越强大。2000年，SunServlet2.3FilterServlet2.4Filter进行了Servlet2.5Filter。Servlet是服务器端用于处理客户端的请求与响应的，而Filter就是介于客户端与服务器端客ServletServletServletAPIFilterFilterMethodCalledbythewebcontainertoindicatetoafilterthatitisbeingtakenoutofdoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainThedoFiltermethodoftheFilteriscalledbythecontainereachtimearequest/responsepairispassedthroughthechainduetoarequestforaresourceattheendofthechain.init(FilterConfigCalledbythewebcontainertoindicatetoafilterthatitisbeingcedintoJavaFilterpublicpublicclassMyFitlerimplementsFilter*init()方法用于Filterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletException}publicvoiddestroy()}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph 路径-- 的路径-- WebServletpublicpublicoServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{PrintWriterout=response.getWriter(); oServlet.</h1>");}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}Webweb.xmlServlet<?<?xmlversion="1.0"encoding="UTF-<web-apph >>WebJSPWebServletJSPServletJSP<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01 <metahttp-equiv="pragma"content="no-<metahttp-equiv="cache-control"content="no-<metahttp-equiv="expires" oServletJSPdoFilter()FilterChaindoFilter()方法publicclassMyFitlerimplementsFilterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletExceptionchain.doFilter(request,response);}publicvoiddestroy()}}Filter的生命周期方法。FilterFilterFilterFilter在每次时执行Filter用于Filter的处理工作FilterFilterJavaFilterpublicpublicclassMyFitler1implementsFilterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletException}publicvoiddestroy()}}JavaFilterpublicpublicclassMyFilter2implementsFilterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletException}publicvoiddestroy()}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph 路径-- 的路径-- 发布Web工程并需要注意的是，FilterChain的doFilter()方法执行时，如果只有一个过滤器的话，执行该方将请求发送给服方法时，才会将请求发送给服务器端的动态或静态资源。如果不是在过滤器链的最后一个过滤器的FilterChain的Webweb.xmlMethodReturnsthefilter-nameofthisMethodReturnsthefilter-nameofthisfilterasdefinedinthedeploymentgetInitParameter(StringReturnsaStringcontainingthevalueofthenamedinitializationparameter,ornulliftheparameterdoesnotexist.Returnsthenamesofthefilter'sinitializationparametersasanEnumerationofStringobjects,oranemptyEnumerationifthefilterhasnoinitializationparameters.ReturnsareferencetotheServletContextinwhichthecallerisJavaFilterpublicpublicclassMyFitlerimplementsFilterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletException}publicvoiddestroy()}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph publicpublicclassMyFitlerimplementsFilterpublicvoidinit(FilterConfigfilterConfig)throws{}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchainthrowsIOExceptionServletException}publicvoiddestroy()}}需要注意的是，通过ServletContext对象获取。Filter过滤器需要配置在web.xml中才能生效。一个过滤器需要配置<filter>和<filter-map>，例<?<?xmlversion="1.0"encoding="UTF-<web-apph 路径-- 的路径-- <filter>配置过滤器的名称实现类以及初始化参数<filter-map>配置当前过滤器的路径<filter-map>中的<url-pattern>用于配置当前过滤器的路径，配置方式与Servlet的<url-如果需要的是Servlet的话，有两种方式配置路径 可以同时配置多个<dispatcher>，如果没有配置<dispatcher>，默认为REQUEST。这四种取值REQUESTServletFORWARDServletFORWARDServletINCLUDEJSP中可以通过<jsp:include>请求某Servlet或调用RequestDispatcher的ERROR：JSP中可以通过<%@pageerrorPage=”error.jsp”>指定错误处理页面，仅这种情况WebWeb应用程序的中文乱码问题，可JavaHttpServletRequestWrapperHttpServletRequest，解决GET方式的中文乱码问题。publicpublicclassMyRequestextendsHttpServletRequestWrapperpublicMyRequest(HttpServletRequestrequest)}publicStringgetParameter(Stringname){Stringvalue=super.getParameter(name);if(getMethod().equalsIgnoreCase("GET")){tryvalue=newString(value.getBytes("ISO-8859-1"),"utf-}catch(UnsupportedEncodingExceptione){}}return}}WebpublicpublicclassEncodingFilterimplementsFilterpublicvoidinit(FilterConfigfilterConfig)throwspublicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchain)throwsIOException,ServletException{MyRequestreq=newMyRequest((HttpServletRequest)request);MyRequestreq=newMyRequest((HttpServletRequest)request);chain.doFilter(req,response);}publicvoiddestroy()}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph JSP<%@<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'login.jsp'starting<formid="userinfo"action="encoding"用户名:<inputtype="text:<inputtype="password"<inputtype="submitvalue="登录<a ServletpublicpublicclassEncodingServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{Stringusername=request.getParameter("username");response.getWriter().println("<h1>username:}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph 所谓自动登录就是当用户第一次登录后，并且选择“自动登录”选项，用户从第二次开始，JSP<%@<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'login.jsp'starting<h3style="color:red;">${msg<formid="userinfo"action="login"用户名:<inputtype="text:<inputtype="password"<inputtype="checkboxname="autologinvalue="true">自动登录<inputtype="submitvalue="登录JavaBeanpublicpublicclassUser{privateStringusername;privateStringpublicStringgetUsername()return}publicvoidsetUsername(Stringusername)this.username=}publicStringgetPassword()return}publicvoidsetPassword(Stringpassword)this.password=}}ServletpublicclassLoginServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doPost(request,}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{Stringusername=request.getParameter("username");Stringpassword=request.getParameter("password");Useruser=newUser();HttpSessionsession=request.getSession();session.setAttribute("user",user);= .setMaxAge(60*60*24*90); }request.setAttribute("msg","用户名 }}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph JSP<%@<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<%@taglibprefix="c" /jsp/jstl/core"<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'index.jsp'starting<c:iftest="${emptyuser<c:iftest="${notemptyuser ，${user.usernamepublicpublicclassAutoLoginFilterimplementsFilterpublicvoidinit(FilterConfigfilterConfig)throwspublicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchain)throwsIOException,ServletExceptionHttpServletRequestreq=if(req.getSession().getAttribute("user")!=chain.doFilter(request, = if ==//没有自动登录信息chain.doFilter(requestresponse);Stringusername Stringpassword= if{chain.doFilter(request,Useruser=newUser();req.getSession().setAttribute("user",user);chain.doFilter(request,response);}}}} s,Stringname)if s==null)return}elsefor s)if .getName().equals(name)) }}return}}publicvoiddestroy()}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-apph JavaBean用于封装用户信息（包含权限信息publicpublicclassUser{privateStringusername;privateStringpassword;privateStringrole;publicStringgetRole()return}publicvoidsetRole(Stringrole)this.role=}publicStringgetUsername()return}publicvoidsetUsername(Stringusername)this.username=}publicStringgetPassword()return}publicvoidsetPassword(Stringpassword)this.password=}}Web<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<%@taglibprefix="c" /jsp/jstl/core"<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'index.jsp'starting<c:iftest="${emptyuser<c:iftest="${notemptyuser ，${user.username<%@<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'userlist.jsp'starting创建管理员可以的功能列表页面<%@<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'adminlist.jsp'startingpublicclassAuthoFilterimplementsFilterprivateFilterConfigprivateMap<String,String>map=newHashMap<String,publicvoidinit(FilterConfigfilterConfig)throws{this.config=}publicvoiddoFilter(ServletRequestrequest,ServletResponseFilterChainchain)throwsIOException,ServletException{Enumerationnames=config.getInitParameterNames();while(names.hasMoreElements())Stringname=(String)names.nex Stringvalue=config.getInitParameter(name);map.put(value,name);}HttpServletRequestreq=(HttpServletRequest)request;Stringpath=for(StringneedPath:ma