There are many extension interfaces PROVIDED by hibernate.
ProxyFactory INTERFACE - used to CREATE proxies
ConnectionProvider interface – used for JDBC connection management
TransactionFactory interface – Used for transaction management
Transaction interface – Used for transaction management
TransactionManagementLookup interface – Used in transaction management.
Cahce interface – provides caching techniques and strategies
CacheProvider interface – same as CACHE interface
ClassPersister interface – provides ORM strategies
IdentifierGenerator interface – used for primary key generation
Dialect abstract class – provides SQL support. 

There are many extension interfaces provided by hibernate.
ProxyFactory interface - used to create proxies
ConnectionProvider interface – used for JDBC connection management
TransactionFactory interface – Used for transaction management
Transaction interface – Used for transaction management
TransactionManagementLookup interface – Used in transaction management.
Cahce interface – provides caching techniques and strategies
CacheProvider interface – same as Cache interface
ClassPersister interface – provides ORM strategies
IdentifierGenerator interface – used for primary key generation
Dialect abstract class – provides SQL support.