登录验证过滤器

LoginCheckFilter.java

package org.guangsoft.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.guangsoft.bean.Users;

import com.google.gson.Gson;

public class LoginCheckFilter implements Filter
{
    @Override
    public void init(FilterConfig filterconfig) throws ServletException
    {
    }

    @Override
    public void doFilter(ServletRequest servletrequest,
            ServletResponse servletresponse, FilterChain filterchain)
            throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest) servletrequest;
        HttpServletResponse response = (HttpServletResponse) servletresponse;
        String option = request.getParameter("option");
        Users user = (Users) request.getSession().getAttribute("user");
        List<String> list = new ArrayList<String>();
        list.add("login");
        list.add("getUsers");
        if (user != null || list.contains(option))
        {
            filterchain.doFilter(servletrequest, servletresponse);
        } 
        else
        {
            response.getWriter().print(new Gson().toJson("login"));
        }
    }

    @Override
    public void destroy()
    {
    }
}

 web.xml

<filter>
        <filter-name>LoginCheckFilter</filter-name>
        <filter-class>org.guangsoft.filter.LoginCheckFilter</filter-class>
</filter>
<filter-mapping>
        <filter-name>LoginCheckFilter</filter-name>
        <url-pattern>*.action</url-pattern>
</filter-mapping>