Accessing multiple database from a Java web application using JPA/EclipseLink/EJB

Question

I have built a simple SOAP java application(server side) and I am using Glassfish4,JPA/EclipseLink,EJB. I have set the db connections(resources/poo

Answer 1

Another solution is creating the persistent context programmatically.

Define an persistent.xml without the connection. Similar to:

persistent.xml

    
        mx.saaskun.model.UserInfo
    

Create a factory for the custom connection:

The method receives two parameters, the custom unit name and the JNDI for the connection.

DynamicResource.java

@Stateless
@LocalBean
public class DynamicResource implements Serializable{
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public EntityManagerFactory getEntityManager(unitName, jndiConnection){
        Map properties = new HashMap();
        properties.put("javax.persistence.jtaDataSource", jndiConnection);
        return Persistence.createEntityManagerFactory(unitName, properties);
    }
}

then you use as:

 public class UserService{
     @EJB
     DynamicResource radResources;

     public List listAll(){
          List();
          String[] databases = new String[]{"jndi/simfin","jndi/simfin2"};
          for(String db:databases){
               List results = listServerUsers("simfin", db);
               allUsers.addAll(results);
          }
          return allUsers;
     }

     protected List listServerUsers(String unitName, String jndi){
         EntityManager em= radResources.getEntityManager(unitName,jndi);
         try {
             Query q = em.createNamedQuery("UserInfo.findAll");
             return (List) q.getResultList();
         } finally {
             em.close();
         }
     }
 }