Web App struts框架里实现Filter.

1 web.xml里添加filter配置信息。

<filter>

<filter-name>Authentication</filter-name>

<filter-class>

com.nova.colimas.web.filters.AuthenticationFilter

</filter-class>

<init-param>

<param-name>onError</param-name>

<param-value>/pages/index.jsp</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>Authentication</filter-name>

<url-pattern>/protect/*</url-pattern>

</filter-mapping>

<filter-class>定义使用com.nova.colimas.web.filters.AuthenticationFilter类执行过滤Action。

<init-param>当验证失败后Forward到/pages/index.jsp

<filter-mapping>只有当地址包括/protect/时运行filter类

2 实现com.nova.colimas.web.filters.AuthenticationFilter

package com.nova.colimas.web.filters;

import java.io.IOException;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.*;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import com.nova.colimas.web.bean.UserBean;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import org.apache.struts.Globals;

import org.apache.struts.action.*;

import com.nova.colimas.web.constants.Constants;

/**

* Filter implementation for user authentication。必须实现Filter接口

* @author tyrone

* @version $Id: AuthenticationFilter.java,v 1.0

*/

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

{

//获得验证失败forward地址

filterConfig = config;

onErrorUrl=filterConfig.getInitParameter("onError");

if (onErrorUrl==null || "".equals(onErrorUrl)){

onErrorUrl="/pages/index.jsp";

}

}

/**

* 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 ServletException,IOException

*/

public void doFilter(ServletRequest request, ServletResponse response, FilterChain next)

throws IOException, ServletException

{

HttpServletRequest httpRequest = (HttpServletRequest)request;

HttpServletResponse httpResponse=(HttpServletResponse)response;

// Current session

HttpSession httpSession = httpRequest.getSession();

//Session里是否有用户信息。

if (httpSession.getAttribute(Constants.USER_KEY) == null)

{

ActionErrors errors=new ActionErrors();

errors.add(ActionErrors.GLOBAL_ERROR,

new ActionError("error authentication"));

httpRequest.setAttribute(Globals.ERROR_KEY,errors);

//没有，验证失败forward到/pages/index.jsp httpRequest.getRequestDispatcher(onErrorUrl).forward(httpRequest,httpResponse);

}else

//成果过滤Action结束

next.doFilter(request,response);

}

/**

* destroy() method is called by the servlet container

*/

public void destroy()

{

}

}