jsp中过滤器选择过滤器的写法详解

public class LoginCheckFilter implements Filter {


private FilterConfig config=null;
private String webroot=null;
public void destroy() {
// TODO Auto-generated method stub


}


@Override
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
HttpServletRequest request=(HttpServletRequest)req;
HttpServletResponse response=(HttpServletResponse)resp;
HttpSession session=request.getSession(false); //取得当前会话的session,没有session也不创建session,同request.getSession()一样


String url=request.getRequestURI(); //获取当前输入的 /项目/当前访问的路径 与我们定义的路径是否相同


if(url!=null&&url.equals(webroot+"/login.jsp")&&url.equals(webroot+"/LoginServlet")){

chain.doFilter(req,resp);
}else{

if(session==null){
response.sendRedirect(webroot+"/login.jsp");

}else{

String user2=(String)session.getAttribute("user1");
if(user2==null){

response.sendRedirect(webroot+"/login.jsp");

}else{

chain.doFilter(request, response);

}
}

}

}


@Override
public void init(FilterConfig config) throws ServletException {
// TODO Auto-generated method stub
this.config=config;
ServletContext ctx=config.getServletContext(); //获取url  /项目名
webroot=ctx.getContextPath();    //项目名


}
}