What is the difference between using multiple @Id in an entity Vs, Composite Id ?
Also, how does this @EmbeddedId work when there is no table actually created separately for the Embedded Object?
Hibernate offers different options for defining/using composite identifiers. All these options are explained in depth in the hibernate reference manual: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html_single/#d0e4819.