org.hibernate.TransientObjectException: object references an unsaved transient instance

When saving an entity having the following property:

@ManyToMany
private Set<Landmark> landmarks;

the following exception might occur:

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.ctb.trust.core.restaurant.domain.Landmark

Set `cascade` as follows:

@ManyToMany(cascade = CascadeType.ALL)
private Set<Landmark> landmarks;

ONLY IF its behavior is appropriate for you.

Otherwise, you can save them manually.

Reference:
http://stackoverflow.com/questions/2302802/object-references-an-unsaved-transient-instance-save-the-transient-instance-be