Outstanding, esp. if you use Hibernate
Spring has a stiff learning curve for many developers, but it's worth it, especially if you use Hibernate and need to better manage transactions. Add on top of that all the other services Spring makes available (like remoting, AOP, JMS, mail, security (Acegi), singleton control, MVC and much more) and you have a stellar platform for enterprise-level applications.
A Web Service API proxy.
Standards-compliant Java persistence via JDO/JPA/REST and RDBMS/MongoDB/Neo4j/Excel/LDAP.