import java.io.IOException;
import java.io.PrintWriter;
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 javax.servlet.http.HttpSession;
import com.ph.entil.Users;
public class LoginFilter implements Filter {
      public LoginFilter() {
            // TODO Auto-generated constructor stub
      }
      public void destroy() {
            // TODO Auto-generated method stub
      }
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
            HttpServletRequest req=(HttpServletRequest) request;
            HttpServletResponse res=(HttpServletResponse) response;
            //获得请求的URL
            String url=req.getRequestURL().toString();
            //获得session中的对象
            HttpSession session= req.getSession();
            Users user=(Users) session.getAttribute("user");
            //使用endsWith()判断url结尾的字符串
            if(url.endsWith("login.jsp") || user!=null || url.endsWith("number1.jsp") || url.endsWith(".css") ||
            url.endsWith(".js")|| url.endsWith(".gif")|| url.endsWith(".png")|| url.endsWith(".jpg")||url.endsWith("SSH_market/")){
                  //满足条件就继续执行
                  chain.doFilter(request, response);
            }else{
            //不满足条件就跳转到其他页面
            PrintWriter out=res.getWriter();
            out.print("<script language>alert('请登录！…………');top.location.href='login.jsp'</script>");
            res.sendRedirect(req.getContextPath() + "/login.jsp");
      }
}
public void init(FilterConfig fConfig) throws ServletException {
}
}

<filter>
<filter-name>LoginFilter</filter-name>
<filter-class>com.ph.filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

该贴由koei转至本版2014-5-2 16:22:05

<filter>
<filter-name>UserFilter</filter-name>
<filter-class>com.filter.UserFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>UserFilter</filter-name>
<url-pattern>/user/*</url-pattern>
</filter-mapping>

public class UserFilter implements Filter{
      //实现了filter接口就需要实现doFilter方法
      public void doFilter(Request req,Response res,FilterChain filter){
            //验证是否已经登录，session中有木有用户的信息
            if(req.getSession().getAttribute("user")!=null){
                  filter.doFilter();//如果有下一个过滤器跳转到下一个，没有跳到指定页面
            }else{//否则的话，跳到登陆页面去
            req.getSession().setAttribute("error","请先登录");
            response.sendRedirect(req.getContextPath()+"/login.jsp");
      }
}
}