Understanding Spring Data JPA repositories common to all entities

Hello,

I am in reference to the following Spring documentation: http://static.springsource.org/sprin...l-repositories

I am trying to understand the logic behind Jpa custom repositories as described above.

My guess is that I have to create a UserRepository interface (in my case User is the specific entity) extending the MyRepository interface and then supply an implementation for it with the proper parameter types. I then have one repository per entity each sharing a number of common methods defined in the MyRepository interface.

This raises a few questions:

One: What if I am performing operations across several entities: which repository do I use?
Two: Does Spring Data Jpa allow for repositories without any type parameters?

Regards,

J.