Fix immutables generation

[eggy03]

Description

Fixed leaking of Immutables generated immutable implementations of abstract classes via service classes, to the public API

Type of Change

Bug fix

Before Immutables was introduced, entity classes were not abstract and did not have the Abstract* prefix either. They were concrete classes and the service classes had these concrete classes as their return type, for example List<DMIProcessor> get();.

After Immutables was introduced, the entity classes were turned into abstract classes and would have the Abstract* prefix in their name. Immutables would scan this and create generated immutable implementations after removing the Abstract* prefix. So, an abstract class AbstractDMIProcessor.class would have an immutable implementation called DMIProcessor.class. This was fine, but entity naming meant the service classes should have returned the abstract instances. Instead, the return type of the service classes retained the pre-Immutable naming scheme, which meant, service classes would now return generated concrete implementations, instead of the actual abstract entities. This caused a leakage of immutable entities to the public API.

It was originally intended for the service classes to de-serialize a JSON to it's immutable instance but return the abstract instance, since all immutable generated sources extend the abstract classes. If there was a need to build a custom instance, something like the following would have been the preferred choice:

DMIProcessor processor = new ImmutableDMIProcessor.Builder().build();
// or
DMIProcessor processor = ImmutableDMIProcessor.copyOf(someOtherProcessor).withSomeMethod(someValue);

where DMIProcessor represents the abstract class and ImmutableDMIProcessor is the generated immutable implementation.

To achieve this, the Abstract* prefix from all the abstract classes have been removed, and Immutable* prefix has been added to all generated immutable implementations. Additionally, two Jackson annotations called @JsonSerialize(as = ImmutableSomeName.class) and @JsonDeserialize(as = ImmutableSomeName.class) has been added to all the entity classes.
These annotations tell the Jackson mappers in the mapping layer to deserialize or serialize the input JSON as the immutable implementations, but when returning the value to the service layer, which is eventually returned to the user, it should be referenced via the abstract entity only.

JSON -> ImmutableDMIProcessor(mapping layer) -> DMIProcessor(service layer)

Obviously, this means you will not be able to access the builder methods, which is intended, because to create your custom builder, you must invoke the Immutable implementations directly. The abstract reference only contains the immutable field values.

Note that this is a BREAKING CHANGE

Breaking Change

• toString() in entity classes no longer returns a pretty-printed JSON. The function has been delegated to toJson() instead.