Java EE 具有在每个请求中运行的过滤器。所有请求都firstwebsite.com将首先在代码中由过滤器处理,然后重定向到secodnwebsite.com.
public class RedirectionFilter implements Filter {
    /**
     * Default constructor.
     */
    public RedirectionFilter () {
        // TODO Auto-generated constructor stub
    }
    /**
     * @see Filter#destroy()
     */
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
            HttpServletRequest request = (HttpServletRequest) req;
            HttpServletResponse response = (HttpServletResponse) res;
            String servletPath = request.getServletPath();
            if (servletPath.endsWith(".html")) {
                response.sendRedirect("http://secondwebsite.com" + servletPath);
            }
            else {
                chain.doFilter(request, response);
            }
}
@Override
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }
}
不要忘记将此过滤器添加到部署描述符 (web.xml)。如果您有其他过滤器,则将其放在首位,以便此过滤器首先运行。
<filter>
    <display-name>RedirectionFilter</display-name>
    <filter-name>RedirectionFilter</filter-name>
    <filter-class>your.package.RedirectionFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>RedirectionFilter</filter-name>
     <servlet-name>Servlet which firstwebsite.com run</servlet-name>
  </filter-mapping>
也可以看看
Servlet 过滤器
过滤器接口