This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
No. But then a relational data model that doesn't define primary keys is arguably broken.
As has been discussed at length in this forum (have a search through the older posts) an entity in a relational database without a primary key cannot be relational so will not work with an Object-Relational Mapping tool. There are partial workarounds (again, a brief search will get you these) but the easiest fix is to correct your data model. Is there a reason you defined an entity without a primary key?