Spring, OpenJPA, multiple persistence unit - spring

Question

There is a spring no-web application Apache James (Java Mail server).
It uses openjpa. It has a persistence unit and datasource and entitymanager factory definition.
I must manipulate it to use one more persistence unit, for an external DB.
I added one more unit into persistence.xml
<persistence-unit name="James" transaction-type="RESOURCE_LOCAL">
<!-- Mailbox stuff-->
<class>org.apache.james.mailbox.jpa.mail.model.JPAMailbox</class>
<class>org.apache.james.mailbox.jpa.mail.model.JPAUserFlag</class>
<class>org.apache.james.mailbox.jpa.mail.model.openjpa.AbstractJPAMessage</class>
<class>org.apache.james.mailbox.jpa.mail.model.openjpa.JPAMessage</class>
<class>org.apache.james.mailbox.jpa.mail.model.openjpa.JPAMessage</class>
<class>org.apache.james.mailbox.jpa.mail.model.JPAProperty</class>
<class>org.apache.james.mailbox.jpa.user.model.JPASubscription</class>
<class>org.apache.james.domainlist.jpa.model.JPADomain</class>
<class>org.apache.james.user.jpa.model.JPAUser</class>
<class>org.apache.james.rrt.jpa.model.JPARecipientRewrite</class>
<properties>
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>
<property name="openjpa.jdbc.MappingDefaults" value="ForeignKeyDeleteAction=cascade, JoinForeignKeyDeleteAction=cascade"/>
<property name="openjpa.jdbc.SchemaFactory" value="native(ForeignKeys=true)"/>
<property name="openjpa.jdbc.QuerySQLCache" value="false"/>
</properties>
</persistence-unit>
<persistence-unit name="myPU" transaction-type="JTA">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>package.EmailAddress</class>
<class>package.Message</class>
<properties>
<property name="javax.persistence.jdbc.user" value="root" />
<property name="javax.persistence.jdbc.password" value="root" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/kepsDb" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="hibernate.hbm2ddl.auto" value="none" />
<property name="hibernate.show_sql" value="false" />
<property name="hibernate.dialect" value=" org.hibernate.dialect.MySQLDialect" />
<property name="hibernate.max_fetch_depth" value="0" />
<property name="hibernate.cache.use_second_level_cache" value="true" />
<property name="hibernate.cache.use_query_cache" value="false" />
<property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory" />
<property name="hibernate.ejb.naming_strategy" value="web.app.persistence.util.AppImprovedNamingStrategy"/>
</properties>
</persistence-unit>
I do not define a second entity manager factory in spring-server.xml, instead, i generate my own entitymanager factory inline with:
EntityManagerFactory emf=Persistence.createEntityManagerFactory("myPU");
EntityManager entityManager=emf.createEntityManager();
entityManager.getTransaction().begin();
But i am getting exception:
Caused by: org.springframework.beans.FatalBeanException: Unable to execute lifecycle method on beanmailetcontext; nested exception is <openjpa-2.1.0-r422266:1071316 nonfatal user error> org.apache.openjpa.persistence.InvalidStateException: This operation cannot be performed while a Transaction is active.

Answer 1

myPU is configured to use JTA transaction. Calling entityManager.getTransaction() when using JTA will cause exception as this method is supposed to use with RESOURCE_LOCAL transaction type .
I don't know if your posted exception messages is due to this , but you can try to change the <persistence-unit> of myPU to :
<persistence-unit name="myPU" transaction-type="RESOURCE_LOCAL">
Please note that if you have to access both databases in the same transaction , you must use JTA .

Answer 2

Following code explains how to configure multiple persistence units with JPA + spring:
First of all, we define two persistence units in the persistence.xml, lets call them unit1 and unit2 respectively:
<persistence 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"
version="1.0">
<persistence-unit name="Unit1" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.archive.autodetection" value="class" />
<property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver" />
<property name="hibernate.connection.url" value="jdbc:oracle:thin:#my.company.com:1522:D1" />
<property name="hibernate.connection.password" value="my_user" />
<property name="hibernate.connection.username" value="my_password" />
</properties>
</persistence-unit>
<persistence-unit name="Unit2" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.archive.autodetection" value="class" />
<property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver" />
<property name="hibernate.connection.url" value="jdbc:oracle:thin:#my.company.com:1522:D2" />
<property name="hibernate.connection.password" value="my_user" />
<property name="hibernate.connection.username" value="my_password" />
</properties>
</persistence-unit>
</persistence>
Since we dealt with a stand-alone Java applicatie, we defined our data sources in the Spring application context, but for web applicaties one typically defines JNDI references to these datasources in the persistence.xml file itself.
From within the application-context.xml these persisetence units are referred to like so:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd">
<context:annotation-config />
<tx:annotation-driven />
<bean id="dataSource1" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="oracle.jdbc.driver.OracleDriver" />
<property name="jdbcUrl" value="jdbc:oracle:thin:#my.company.com:1521:D1" />
<property name="user" value="my_user" />
<property name="password" value="my_password" />
</bean>
<bean id="dataSource2" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
<property name="url" value="jdbc:oracle:thin:#my.company.com:1521:D2" />
<property name="username" value="my_user" />
<property name="password" value="my_password" />
</bean>
<!-- DEFINITION OF BOTH ENTITY MANAGER FACTORIES -->
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource1" />
<property name="persistenceUnitName" value="Unit1" />
<property name="persistenceUnitManager" ref="persistenceUnitManager" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="databasePlatform"
value="org.hibernate.dialect.Oracle10gDialect" />
</bean>
</property>
</bean>
<bean id="entityManagerFactory2"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource2" />
<property name="persistenceUnitName" value="Unit2" />
<property name="persistenceUnitManager" ref="persistenceUnitManager" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="databasePlatform"
value="org.hibernate.dialect.Oracle10gDialect" />
</bean>
</property>
</bean>
<!-- PERSISTENCE UNIT MANAGER and TRANSACTION MANAGERS -->
<bean id="persistenceUnitManager"
class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
<property name="dataSources">
<map>
<entry key="d1" value-ref="dataSource1" />
<entry key="d2" value-ref="dataSource2" />
</map>
</property>
</bean>
<bean id="transactionManager"
class="org.springframework.orm.jpa.JpaTransactionManager"
p:entity-manager-factory-ref="entityManagerFactory" />
<bean id="abwTransactionManager"
class="org.springframework.orm.jpa.JpaTransactionManager"
p:entity-manager-factory-ref="entityManagerFactory2" />
</beans>
Now all that is left to do is denote the #PersistenceContext in your DAOs like so:
#Required
#PersistenceContext(unitName = "Unit1")
public void setEntityManager(final EntityManager entityManager) {
this.entityManager = entityManager;
}