For clearer terminology on various keys, refer this article.
Primary key mapping
Primary key or surrogate key of an entity can be mapped in 2 ways : xml and annotations.
Xml way :
<id> tag is used to map primary key or surrogate key in hibernate, with <generator> for the field.
Annotation method:
For this @Id is used for the same. For auto generated use @GeneratedValue.
If the primary key and the Natural key for an entity is the same, which means we are assigning the value on our own, then we need to skip the <generator> tag in the xml file and @GeneratedValue when using hibernate.
Natural key mapping
For an entity with seperate natural key, we can use <natural-id> tag in xml and similar @NaturalId annotation.
