What the difference between providers DATANUCLEUS and DATANUCLEUS_2 in Spring Roo?

Can anyone tell me the difference between theses two commands?

开发者_如何学编程

persistence setup --provider DATANUCLEUS --database H2_IN_MEMORY

persistence setup --provider DATANUCLEUS_2 --database H2_IN_MEMORY

What's dnucleus_2??

Thank you

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Have a look at this part of the Roo Reference Documentation:

http://static.springsource.org/spring-roo/reference/html/base-persistence.html

The relevant part of the page notes that ...

Version 1 does not support JPA 2 and should only be used if you are intending to deploy to Google App Engine. Version 2 should be used if you are intending to deploy to VMforce cloud environments.

So, for AppEngine use DATANUCLEUS, and for anything that uses JPA 2 (including VMForce) use DATANUCLEUS_2.