Eclipse Plug-in : Displaying warning message in Eclipse using AST , DOM

Question

I am learning Plug-in development and code manipulation using Abstract Syntax Tree and DOM.
I want to code a plug-in which will display a warning (see image) on the left hand side of the Eclipse Java code editor based on some condition in the testing code.

example scenario :
Right now warning message is displayed in eclipse when we do not use any declared variable in Java. I want to display warning message when (Just for example) any variable is assigned value 10 (lets say).
I know how to create Plug-In, Extract variables, expressions and declaration using AST. But I have no idea about how to display warning message.

which API or package is used for it?
Can someone please show me the path for this?

Answer 1

You can achieve the same using eclipse markers (IMarker).
Refer below link for more details on how to create an eclipse marker.

https://www.eclipse.org/articles/Article-Mark%20My%20Words/mark-my-words.html

The MarkerUtilities class provides methods to create markers easily.
You need to add the org.eclipse.ui.editors plug-in to the dependencies.

For showing the same in editor use markerAnnotationSpecification extension point. This is used to define a mapping between markers and editor annotations automatically, with specified formatting.

Refer: http://cubussapiens.hu/2011/05/custom-markers-and-annotations-the-bright-side-of-eclipse/