[jboss-dev-forums] [JBoss AS7 Development] - Re: jboss7 quickstarts entitymanager injection question

[Scott Marlow]

Scott Marlow [http://community.jboss.org/people/smarlow] created the discussion

"Re: jboss7 quickstarts entitymanager injection question"

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Robert,

That is really an application level concern, whether each application has its own datasource or uses separate datasources.  If it helps, think of the data source, in terms of database server connections.  Each data source is capable of handing out a number of database connections, that are used by the JPA persistence provider to create/read/update/delete entities.  

The H2 ( http://en.wikipedia.org/wiki/H2_%28DBMS%29 http://en.wikipedia.org/wiki/H2_%28DBMS%29) database and other database engines, are capable of performing several operations at the same time, each occuring on a separate database connection.

If two separate applications are sharing the same datasource, that just means they are sharing the database connection pool associated with that datasource.  The applications could also be sharing tables or they could each have there own separate tables on the database.  Sharing tables, between applications is not an attractive idea but its been done.  When sharing tables, you would probably have to avoid caching data in memory (via JPA second level cache) but otherwise, would work fine.  If you can have a separate database per application, that is wonderful but sometimes its not possible.  

Scott
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