I have requirement to migrate old style spring project to Spring boot. Assume below code snippet I have to migrate to Spring boot style.
Here my ask , how to conver
There is no need in converting this code. You only need to make the classes that extend com.test.core.common.AbstractClass declared as spring managed beans by either annotating them with @Component or @Service or declaring a method annotated with @Bean in your configuration class.
Generally "abstract bean" is not needed in Java Configuration, there is even no equivalent. It was needed in xml configuration for parameter inheritance which is now achievable with plain java methods. Find example from Stephane Nicoll who is Spring Core developer.