public interface DocumentId implements Annotation
Annotation used to mark a POJO property to be automatically populated with the document's ID when the POJO is created from a Cloud Firestore document (for example, via DocumentSnapshot#toObject).
Any of the following will throw a runtime exception:
- This annotation is applied to a property of a type other than String or DocumentReference.
- This annotation is applied to a property that is not writable (for example, a Java Bean getter without a backing field).
- This annotation is applied to a property with a name that conflicts with a read document
field. For example, if a POJO has a field
firstNameannotated by @DocumentId, and there is a property from the document named
firstNameas well, an exception is thrown when you try to read the document into the POJO via DocumentSnapshot#toObject or DocumentReference#get.
When using a POJO to write to a document (via DocumentReference#set or @WriteBatch#set), the property annotated by @DocumentId is ignored, which allows writing the POJO back to any document, even if it's not the origin of the POJO.