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

}

}