Entity State Detection Strategies

The following table describes the strategies that Spring Data offers for detecting whether an entity is new:

Table 1. Options for detection whether an entity is new in Spring Data
`@Id`-Property inspection (the default)	By default, Spring Data inspects the identifier property of the given entity. If the identifier property is `null` or `0` in case of primitive types, then the entity is assumed to be new. Otherwise, it is assumed to not be new.
`@Version`-Property inspection	If a property annotated with `@Version` is present and `null`, or in case of a version property of primitive type `0` the entity is considered new. If the version property is present but has a different value, the entity is considered to not be new. If no version property is present Spring Data falls back to inspection of the identifier property.
Implementing `Persistable`	If an entity implements `Persistable`, Spring Data delegates the new detection to the `isNew(…)` method of the entity. See the Javadoc for details. Note: Properties of `Persistable` will get detected and persisted if you use `AccessType.PROPERTY`. To avoid that, use `@Transient`.
Providing a custom `EntityInformation` implementation	You can customize the `EntityInformation` abstraction used in the repository base implementation by creating a subclass of the module specific repository factory and overriding the `getEntityInformation(…)` method. You then have to register the custom implementation of module specific repository factory as a Spring bean. Note that this should rarely be necessary.