Java SDK报错java.lang.ClassNotFoundException: io.netty.channel.EventLoopGroup

public class MyConn {
    //static Connection con;

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        push();
    }

    private static void push(){
        String masterSecret = "";
        String appKey = "04bd460f6bdd561d26c7d660";
        JPushClient jPushClient = new JPushClient(masterSecret, appKey);
        PushPayload payload = PushPayload.newBuilder()
                .setPlatform(Platform.all())
                .setAudience(Audience.all())
                .setNotification(Notification.alert("jpush text1"))
                .setMessage(Message.content("jpush test2"))
                .build();

        try {
            PushResult result =  jPushClient.sendPush(payload);
            System.out.print(result.msg_id);
            System.out.print(result.sendno);
        } catch (APIConnectionException e) {
            System.out.println("conn error");
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (APIRequestException e) {
            System.out.println("request error");
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}