Chapter 2 : Entities Item 13: How to Adopt a Fluent API Style in Entities FluentApiOnSetters FluentApiAdditionalMethods Item 14: How to Populate a Child-Side Parent Association via a Hibernate-Specific Proxy PopulatingChildViaProxy Item 15: How to Use Java 8 Optional in Persistence Layer Optional Item 16: How to Write Immutable Entities ImmutableEntity Item 17: How to Clone Entities CloneEntity Item 18: Why and How to Activate Dirty Tracking EnableDirtyTracking Item 19: How to Map a Boolean to a Yes/No MapBooleanToYesNo Item 20: The Best Way to Publish Domain Events from Aggregate Roots DomainEvents