multiple databases configuration

[bartdp]

I searched the forum/google and didn't find a right solution yet.
The user has to logon with his username/password and choose which db to use (radio button)
Then the application has to authenticate the user in the choosen db and work further in that db.
This is how I have configured my seam application:

Components.xml

        <persistence:entity-manager-factory name="entityManagerFactory0"
                persistence-unit-name="ddsPersistenceUnit0" />

        <persistence:entity-manager-factory name="entityManagerFactory1"
                persistence-unit-name="ddsPersistenceUnit1" />

        <persistence:managed-persistence-context name="entityManager0"
                auto-create="true" entity-manager-factory="#{entityManagerFactory0}" />

        <persistence:managed-persistence-context name="entityManager1"
                auto-create="true" entity-manager-factory="#{entityManagerFactory1}" />

context.xml

<Context path="/test" docBase="test" debug="5" reloadable="true"
        crossContext="true">

        <Resource name="datasource0"
                driverClassName="oracle.jdbc.driver.OracleDriver"
                factory="org.apache.commons.dbcp.BasicDataSourceFactory" maxActive="2"
                maxIdle="1" maxWait="10000" auth="Container"
                password="user0" type="javax.sql.DataSource"
                url="jdbc:oracle:thin:@..."
                username="user0" />

        <Resource name="datasource1" 
                driverClassName="com.mysql.jdbc.Driver" auth="Container"
                factory="org.apache.commons.dbcp.BasicDataSourceFactory" maxActive="2"
                maxIdle="1" maxWait="10000" type="javax.sql.DataSource"
                url="jdbc:mysql://localhost:3306/testseam" username="root" />

</Context>

persistent.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
        xmlns="http://java.sun.com/xml/ns/persistence"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
        
        <persistence-unit name="persistence0" transaction-type="RESOURCE_LOCAL">
                <provider>org.hibernate.ejb.HibernatePersistence</provider>
                <jta-data-source>java:comp/env/datasource0</jta-data-source>
                <properties>
                        <property name="hibernate.default_schema" value="test" />
                        <property name="hibernate.connection.autocommit" value="false" />
                        <property name="hibernate.show_sql" value="true" />
                        <property name="hibernate.format_sql" value="true" />
                        <property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider" />
                        <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect" />
                        <property name="hibernate.cache.provider_configuration_file_resource_path" value="ehcache.xml" />
                        <property name="hibernate.cache.use_second_level_cache" value="true" />
                        <property name="hibernate.cache.use_query_cache" value="true" />
                </properties>
        </persistence-unit>
        
        <persistence-unit name="persistenceUnit1" transaction-type="RESOURCE_LOCAL">
                <provider>org.hibernate.ejb.HibernatePersistence</provider>
                <jta-data-source>java:comp/env/datasource1</jta-data-source>
                <properties>
                        <property name="hibernate.connection.autocommit" value="false" />
                        <property name="hibernate.show_sql" value="true" />
                        <property name="hibernate.format_sql" value="true" />
                        <property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider" />
                        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
                        <property name="hibernate.cache.provider_configuration_file_resource_path" value="ehcache.xml" />
                        <property name="hibernate.cache.use_second_level_cache" value="true" />
                        <property name="hibernate.cache.use_query_cache" value="true" />
                </properties>
        </persistence-unit>
</persistence>

My first db is an oracle db and the second a mysql.
Now, I'm making a generic data service class where I define the transactional methods.
Here I'm a little confused, not knowing how to solve the problem.
GenericDataServiceImpl.java

public abstract class GenericDataServiceImpl<T, ID extends Serializable>
                implements GenericDataService<T, ID> {

        private Class<T> persistentClass;

        @In
        protected EntityManager entityManager0;

        @In
        protected EntityManager entityManager1;

        @SuppressWarnings("unchecked")
        public GenericDataServiceImpl() {
                this.persistentClass = getPersistentClass();
        }

        protected abstract Class<T> getPersistentClass();

        @Transactional
        public void removeEntity(T entity) {
                entityManager1.remove(entity);
        }

        @Transactional
        public void persistEntity(T entity) {
                entityManager1.persist(entity);
        }

Do I have to write an if-statement where I choose the right entityManager for each method or is there a better solution?

[bartdp]

I know how I can solve this with spring integrated, but I'm searching for a seam-only solution.

[gjeudy]

There is no seam out of the box solution for this afaik. I had to deal with a similar problem and instead of injecting all entitymanagers with annotations I injected my service locator object then based on arguments passed to the service locator I would lookup one entitymanager or another from JNDI.

JBoss allows you to publish transactional entity manager in the global JNDI context by adding the following line in your persistence.xml

<property name="jboss.entity.manager.jndi.name" value="java:/rdm-sdEntityManager" />

The beauty of this is that no matter from where you do the JNDI lookup you will always get an entityManager that is guaranteed to participate in the current transaction.

[bartdp]

I think you mean:

<property name="jboss.entity.manager.factory.jndi.name" value="java:/rdm-sdEntityManager"/>

So you used a service locator pattern.
Instead of:

        @In
        protected EntityManager entityManager0;

        @In
        protected EntityManager entityManager1;

in my GenericDataServiceImpl, I have to lookup (using the service locator) the right entityManager?

[gjeudy]

Yes thats right, DI purists will think it wrong to do a JNDI lookup but I dont see a better solution especially if you have many datasources. I made it so that the JNDI name follows a certain pattern to facilitate the lookup.

In any case your DAO is still isolated of the lookup conditionals hidden behind the service locator interface.

[bartdp]

Thanks for the response.

Is it maybe possible to copy/paste a little code here, that would be interesting not only for me, but for a lot of people who has the same problem.

Thx