加个 SessionIdHandler：
public class SessionIdHandler extends Handler {

@Override
public void handle(String target, HttpServletRequest request,
HttpServletResponse response, boolean[] isHandled) {
// L.cm update by 2014-08-06 更精准的判断
boolean isFromURL = request.isRequestedSessionIdFromURL();
if (isFromURL) {
target = target.substring(0, target.indexOf(';'));
}
next.handle(target, request, response, isHandled);
}

}

具体代码在这里：
https://gitee.com/596392912/JFinal-commons/blob/master/src/main/java/com/siweifu/ext/handler/SessionIdHandler.java

最后配置一下：
me.add(new SessionIdHandler());

这个问题本质上与 jfinal 无关