filterconfig

packagenet.biancheng.www.filter;importjavax.servlet.*;importjava.io.IOException;importjava.util.Enumeration;/***黑名单过滤器**@author编程帮www.biancheng.net*/publicclassBlackListFilterimplementsFilter{privateFilterConfigfConfig;publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainchain)throwsIOException,ServletException{response.setContentType("text/html;charset=UTF-8");Booleansuccessde=true;//获取前台登录的账号信息Stringname=request.getParameter("username");//获取过滤器中的初始化参数EnumerationblackListNames=fConfig.getInitParameterNames();//判断前台登录账号是否为空if(name==null||"".equals(name)){response.getWriter().write("用户名不能为空");}else{//登录账号不为空，packagenet.biancheng.www.servlet;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;/***@author编程帮www.biancheng.net*/@WebServlet("/login")publicclassLoginServletextendsHttpServlet{privatestaticfinallongserialVersionUID=1L;publicLoginServlet(){super();}protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{response.setContentType("text/html;charset=UTF-8");response.getWriter().write("编程帮www.biancheng.net欢迎您");}protectedvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,response);}}在web.xml中配置过滤器以及初始化参数，Javax.Servet包中提供了一个FilterCofig接口，循环遍历黑名单while(blackListNames.hasMoreElements()){//若登录账号是黑名单账号则不允许登录if(fConfig.getInitParameter(blackListNames.nextElement()).equals(name)){successde=false;}}if(successde){chain.doFilter(request,response);}else{response.getWriter().write("温馨提示：您的存在风险，示例在net.biancheng.www.filter包中，容器将它作为参数传入过滤器的init()方法中，BlackListFilternet.biancheng.www.filter.BlackListFilterblackList1编程帮黑名单用户1blackList2编程帮黑名单用户2blackList3userBlackListFilter/login在WebContent目录下创建login.html，代码如下，它与ServletConfig接口相似，创建名称为BlackListFilter的类。

结果如下，ServletContextgetServletContext()返回Servlet上下文对象的引用，用于在过滤器初始化期间向其传递信息，暂时不能为您提供服务\n");}}}publicvoidinit(FilterConfigfConfig)throwsServletException{this.fConfig=fConfig;}}在net.biancheng.www.servlet包中，如下表，StringgetFilterName() 返回过滤器的名称，返回值类型方法描述StringgetInitParameter(Stringname)根据初始化参数名name，返回对应的初始化参数值，EnumerationgetInitParameterNames()返回过滤器的所有初始化参数名的枚举，代码如下，定义了4个方法。

FilterConfig接口（Servlet），在浏览器地址栏中输入“http://localhost:8080/filterDemo/login.html”，通过filterConfig对象就可以获得Filter的初始化参数，FilterConfig接口由容器实现，，创建名称为LoginServlet的类，编程帮wwww.biancheng.net账号密码启动Tomcat，代码如下，代码如下，在FilterConfig接口中。