I have written a demo gadget with the help of https://developer.atlassian.com/server/jira/platform/writing-gadgets-for-jira/ but the main difference is in this link gadget is created through atlassian-sdk-plugin
I did the following steps
1) I download the zip provided in the link.
2) To import it in eclipse ide I ran atlas-mvn eclipse:eclipse which added the eclipse file on the project which helped me to import project in eclipse.
3) Without changing anything in the code, I exported the jar from eclipse and in the manage apps section in jira I uploaded the jar file, without any error, it uploaded successfully.
4) But in My Dashboard when I searched for the gadget I added(Named-Test Jira Tutorial Gadget") it was not available.
Help will more appreciable