在过滤器中重定向时停止进一步处理

只需

return

if

if (sn.startsWith("www.")) {    String url = "http://" + getDefaultDomain() + req.getContextPath() + req.getRequestURI();    HttpServletResponse resp = (HttpServletResponse) response;    resp.reset();    resp.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);    resp.setHeader("Location", url);    return;}chain.doFilter(request, response);

或添加一个

else

if (sn.startsWith("www.")) {    String url = "http://" + getDefaultDomain() + req.getContextPath() + req.getRequestURI();    HttpServletResponse resp = (HttpServletResponse) response;    resp.reset();    resp.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);    resp.setHeader("Location", url);} else {    chain.doFilter(request, response);}