public class TestFillter implements Filter{

@Override

public void destroy() {

}

@Override

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)

throws IOException, ServletException {

HttpServletRequest request=(HttpServletRequest) arg0;

HttpServletResponse response=(HttpServletResponse) arg1;

String name=request.getHeader("PARA_TOKEN");

if(name!=null)

                  {

arg2.doFilter(request, response);

                        return;

                   }

//否则返回主界面

response.sendRedirect(request.getContextPath()+"/");

}

@Override

public void init(FilterConfig arg0) throws ServletException {

}

}