1 Reply Latest reply on Dec 3, 2010 5:33 AM by viggo.navarsete

Dinamically switch DataSource in EJB3 application

sergerus Dec 3, 2010 4:59 AM

Is there a way to dinamically switch EntityManager's DataSource to working with more then one datanase? For this time I found only way described here:

http://community.jboss.org/message/356772

"bill.burke@jboss.com" wrote:
deploy your entities as you would but assign them a JNDI name(see docs). In your EJB interceptor pick the appropriate JNDI name of the EntityManager you want to access. Either inject the ENtityManager into the field of your bean using a custom annotation, or stuff the chosen entity manager into a java.lang.ThreadLocal. This way you still get the automatic session management that the EJB/Java Persistence integration gives you. Following me?

1. Re: Dinamically switch DataSource in EJB3 application

viggo.navarsete Dec 3, 2010 5:33 AM (in response to sergerus)

Hi,

if you know the JNDI names of the datasources that you want to switch between, you can do it like this:

private Map<String, EntityManager> cachedEntityManagerMap = new HashMap<String, EntityManager>(); // cached EntityManagers

private EntityManager getEntityManager() {
String jndiName = "java:/something/someDS"; // TODO: Here you need to determine the JNDI name of the DataSource you want to switch to!
log.info( "Change datasource to '" + jndiName + "'" );

if( cachedEntityManagerMap.containsKey( jndiName ) ) { // if already created, return a cached version instead of creating a new
log.debug( "Return cached EntityManager with jndiName '" + jndiName + "'" );
return cachedEntityManagerMap.get( jndiName );
} else {
log.debug( "Return new EntityManager with jndiName '" + jndiName + "'" );
/*
* See "Hibernate Entity Manager User Guide", chapter "Bootstrapping" for more examples of what to override in
* the map
*/
Map<String, String> emMap = new HashMap<String, String>();
emMap.put( "javax.persistence.jtaDataSource", jndiName );
EntityManager em = Persistence.createEntityManagerFactory( "somePU", emMap )
.createEntityManager();
cachedEntityManagerMap.put( jndiName, em );
return em;
}
private EntityManager getEntityManager() {
String jndiName = "java:/something/someDS"; // TODO: Here you need to determine the JNDI name of the DataSource you want to switch to!
log.info( "Change datasource to '" + jndiName + "'" );

if( cachedEntityManagerMap.containsKey( jndiName ) ) { // if already created, return a cached version instead of creating a new
log.debug( "Return cached EntityManager with jndiName '" + jndiName + "'" );
return cachedEntityManagerMap.get( jndiName );
} else {
log.debug( "Return new EntityManager with jndiName '" + jndiName + "'" );
/*
* See "Hibernate Entity Manager User Guide", chapter "Bootstrapping" for more examples of what to override in
* the map
*/
Map<String, String> emMap = new HashMap<String, String>();
emMap.put( "javax.persistence.jtaDataSource", jndiName );
EntityManager em = Persistence.createEntityManagerFactory( "somePU", emMap )
.createEntityManager();
cachedEntityManagerMap.put( jndiName, em );
return em;
}
}
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