Web App struts框架裡實現Filter

　　 webxml裡添加filter配置信息
　　<filter>
　　<filtername>Authentication</filtername>
　　<filterclass>
　　limaswebfiltersAuthenticationFilter
　　</filterclass>
　　<initparam>
　　<paramname>onError</paramname>
　　<paramvalue>/pages/indexjsp</paramvalue>
　　</initparam>
　　</filter>
　　<filtermapping>
　　<filtername>Authentication</filtername>
　　<urlpattern>/protect/*</urlpattern>
　　</filtermapping>
　　<filterclass>定義使用limaswebfiltersAuthenticationFilter類執行過濾Action
　　<initparam>當驗證失敗後Forward到/pages/indexjsp
　　<filtermapping>只有當地址包括/protect/時運行filter類
　　
　　 實現limaswebfiltersAuthenticationFilter
　　package limaswebfilters;
　　import javaioIOException;
　　import javaxservletRequestDispatcher;
　　import javaxservletServletException;
　　import javaxservlethttp*;
　　import javaxservletFilter;import javaxservletFilterChain;
　　import javaxservletFilterConfig;
　　import limaswebbeanUserBean;
　　import javaxservletServletRequest;
　　import javaxservletServletResponse;import orgapachestrutsGlobals;
　　import orgapachestrutsaction*;
　　import nstantsConstants;
　　/**
　　* Filter implementation for user authentication必須實現Filter接口
　　* @author tyrone * @version $Id: AuthenticationFilterjavav
　　*/public class AuthenticationFilter implements Filter{
　　/**
　　* filterConfig will store the reference of FilterConfig
　　*/　 private FilterConfig filterConfig;
　　private String onErrorUrl;
　　/**
　　* store the reference of the FilterConfig
　　* @param config FilterConfig object
　　* @throws ServletException
　　*/　 public void init(FilterConfig config) throws ServletException
　　{//獲得驗證失敗forward地址
　　filterConfig = config;
　　onErrorUrl=filterConfiggetInitParameter(onError);
　　if (onErrorUrl==null || equals(onErrorUrl)){
　　onErrorUrl=/pages/indexjsp;
　　}
　　}
　　/**
　　* User Authentication is　done If User is authenticated successful then
　　* control is transferred to logon URI
　　* @param ServletRequest Request
　　* @param ServletRequest Response
　　* @param FilterChain Filter Chain
　　* @throws ServletExceptionIOException
　　*/　 public void doFilter(ServletRequest request ServletResponse response FilterChain next)
　　throws IOException ServletException
　　{
　　HttpServletRequest httpRequest = (HttpServletRequest)request;
　　HttpServletResponse httpResponse=(HttpServletResponse)response;
　　// Current session
　　HttpSession httpSession = ();
　　//Session裡是否有用戶信息
　　if ((ConstantsUSER_KEY) == null)
　　{
　　ActionErrors errors=new ActionErrors();
　　errorsadd(ActionErrorsGLOBAL_ERROR
　　new ActionError(error authentication));
　　(GlobalsERROR_KEYerrors);
　　//沒有驗證失敗forward到/pages/indexjsp
　　(onErrorUrl)forward(httpRequesthttpResponse);
　　}else//成果過濾Action結束
　　nextdoFilter(requestresponse);
　　}
　　/**
　　* destroy() method is called by the servlet container
　　*/　 public void destroy()
　　{
　　}
　　}

From:http://tw.wingwit.com/Article/program/Java/ky/201311/28400.html