VERY simple multiple datasources

[hardaur]

Greetings all,

  I have a project that requires me to use multiple datasources.  I've done a fair amount of searching but my example is MUCH more simplistic than all of the other stuff I'm seeing out there (ie, XA stuff, etc).  I figure there must be a very simple way of doing is so thought I'd ask.

  The situation is that I have my Seam app database, I also have a database that drives my external portal.  Finally, I'm authenticating externally to both of these databases (LDAP via CAS).  ALL I need to do is when a user logs in, if he's not in the Seam database simply do a single query to the portal database to retrieve the user's info.  That's it : /

  I realize I need to create another datasource in components.xml, and create an entity for the portal db table, but how do I tell the entity to use the 2nd datasource?  Am I way off base with how simple it is?

Thanks!
Gerald

[scatudal]

Hi Gerald,
I did something similar for a project I'm working on.  I added a no-tx-datasource in my datasource file and than added another persistence unit in my persistence.xml file.  This new persistence unit is not managed by seam because I don't need it to be.  I think it's the same for you.  Then you just need to have you persistence context injected by the container like this :

     @PersistenceContext( unitName = "whateverYouNameIt" )
     EntityManager whateverYouNameIt;

Note that for the container to inject the persistence context, the class must be an EJB.

Hope this helps.

Sylvain

[hardaur]

Sylvain,

  Thanks very much for your response!  Unfortunately the Seam app is a mature WAR app, not EJB.  Anyway to do something similar in that situation?  It seems you are right on the money as to what I'm after though.

Gerald

[scatudal]

I don't have time to test it, but here is what I would try:

Add a no-tx-datasource datasource in whatever-ds.xml :

     <no-tx-datasource>
          <jndi-name>fooDatasource</jndi-name>
          <connection-url>...</connection-url>
          <driver-class>...</driver-class>
          <user-name>...</user-name>
          <password>...</password>
     </no-tx-datasource>

Add a persistence unit in persistence.xml :

   <persistence-unit name="foo">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
      <jta-data-source>java:/fooDatasource</jta-data-source>
      <properties>
         <property name="hibernate.dialect" value="..."/>
         <property name="hibernate.show_sql" value="false"/>
         <property name="hibernate.format_sql" value="false"/>
         <property name="jboss.entity.manager.factory.jndi.name" 
                   value="java:/fooEntityManagerFactory"/>
      </properties>

   </persistence-unit>

And finally add a new managed persistence context in component.xml :

     <persistence:managed-persistence-context
          name="fooEntityManager" auto-create="true" 
                persistence-unit-jndi-name="java:/fooEntityManagerFactory"  />

You should now be able to have seam inject an EntityManager with this :

     @In
     EntityManager fooEntityManager;

Hoping I'm not misleading you! ;)

Sylvain

[hardaur]

With some minor tweaking due to my specific configuration, that was it ; )

Thanks!

Gerald

[asookazian]

What are the differences between using <local-tx-datasource> vs. <no-tx-datasource> in foo-ds.xml?

Does this cause JPA not to use the cache, for example?  Or is it a performance optimization in the case of using JDBC/sprocs?

[scatudal]

local-tx-datasource is Transactional while no-tx-datasource is not transactional.

If you need to have both connection transactional, you'll need to read a bit because I haven't done that yet.

Here is a link where you can get more info : Configuring JDBC DataSources

Sylvain

[jeanluc]

You need to select the datasource according to the nature of the data source. That is, select <no-tx-datasource> if the data source is not transactional (such as an LDAP source or something using file system operations, for instance).