http://javers.org is library that does exacly what you need: has methods like compare(Object leftGraph, Object rightGraph) returning the Diff object. Diff contains a list of changes (ReferenceChange, ValueChange, PropertyChange) e.g.

given:
DummyUser user =  dummyUser("id").withSex(FEMALE).build();
DummyUser user2 = dummyUser("id").withSex(MALE).build();
Javers javers = JaversTestBuilder.newInstance()

when:
Diff diff = javers.compare(user, user2)

then:
diff.changes.size() == 1
ValueChange change = diff.changes[0]
change.leftValue == FEMALE
change.rightValue == MALE

It can handle cycles in graphs.

In addition you can get Snapshot of any graph object. Javers has JSON serializers and deserializers to snapshot, and changes so you can easily save them in database. With this library you can easily implement a module for auditing.