configure Spring+Hibernate+JPA for work with two databases

第一方案
my datasource-context.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
 xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
  http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
  http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd
  http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.5.xsd"
 xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx"
 xmlns:util="http://www.springframework.org/schema/util">

 <!--
 Data Source config
  -->
 <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
  destroy-method="close" p:driverClassName="${local.jdbc.driver}" p:url="${local.jdbc.url}"
  p:username="${local.jdbc.username}" p:password="${local.jdbc.password}">
 </bean>

 <bean id="dataSourceRemote" class="org.apache.commons.dbcp.BasicDataSource"
  destroy-method="close" p:driverClassName="${remote.jdbc.driver}"
  p:url="${remote.jdbc.url}" p:username="${remote.jdbc.username}"
  p:password="${remote.jdbc.password}" />

 <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"
  p:entity-manager-factory-ref="entityManagerFactory" />

 <!--
    JPA config  
    -->
 <tx:annotation-driven transaction-manager="transactionManager" />

 <bean id="persistenceUnitManager"
  class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
        <property name="persistenceXmlLocations">
   <list value-type="java.lang.String">
    <value>classpath*:config/persistence.local.xml</value>
    <value>classpath*:config/persistence.remote.xml</value>
   </list>
  </property>

  <property name="dataSources">
   <map>
    <entry key="localDataSource" value-ref="dataSource" />
    <entry key="remoteDataSource" value-ref="dataSourceRemote" />
   </map>
  </property>
  <property name="defaultDataSource" ref="dataSource" />
 </bean>

 <bean id="entityManagerFactory"
  class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  <property name="jpaVendorAdapter">
   <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"
    p:showSql="true" p:generateDdl="true">
   </bean>
  </property>
  <property name="persistenceUnitManager" ref="persistenceUnitManager" />

 </bean>

 <bean
  class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

</beans>

each persistence.xml contains one unit, like this:

<persistence-unit name="remote" transaction-type="RESOURCE_LOCAL">
  <properties>
   <property name="hibernate.ejb.naming_strategy" value="org.hibernate.cfg.DefaultNamingStrategy" />
   <property name="hibernate.dialect" value="${remote.hibernate.dialect}" />
   <property name="hibernate.hbm2ddl.auto" value="${remote.hibernate.hbm2ddl.auto}" />
  </properties>
 </persistence-unit>


   1.

      In your Spring context:

      <context:annotation-config />

   2.

      In your Spring-managed DAOs (note the unitName property):

      @PersistenceContext(unitName = "pu1"`) protected EntityManager entityManager;

This way a properly intantiated EntityManager corresponding to the persistence unit named "pu1" would be injected in the corresponding DAOs.
   
第二方案
If you follow this tutorial, http://javacodegeeks.blogspot.com/2010/05/jboss-42x-spring-3-jpa-hibernate.html you can make the following changes to access two different databases:

   1. persistence.xml, define a second pesristence-unit for your second database.
   2. spring.xml, define a second entityManagerFactory bean under a different name, lets say "entityManagerFactoryDB2" and configure it to use the persistent unit for the second database.
   3.

      for every DAO you want to access the second database include the following :

      @Autowired
      private EntityManagerFactory entityManagerFactoryDB2;


      @PostConstruct
      public void init() {
          super.setEntityManagerFactory(entityManagerFactoryDB2);
      }

Thats all!

On spring service classes, use the DAOs as usual!