Validate custom field values on button click event

[Yogesh Mude]

Hi Team,

I have worked on the plugin which will add one button using the web panel to issue view screen.

Now I wanted to validate the custom field value on this button click event whether that custom field contains the value or not. if not, then it should show a message about it.

Any idea how i can handle this or anybody has gone through this.

Thanks in advance.