I added a new internal item to check java_gateway availability, the item is the documented: zabbix[java,,ping], I then added a trigger using the nodata(60) function in order to get an alarm if java gateway crashes, unfortunately, when zabbix java gateway goes down for any reason (be it crash, or be it just stopping the service), the item turns into NOT SUPPORTED, making the nodata() trigger unusable.

Here's the message appearing in the zabbix_server.log:

24045:20140408:112627.634 item [Zabbix Server:zabbix[java,,ping]] became not supported: cannot connect to [[127.0.0.1]:10052]: [111] Connection refused