Override Datasource definition in LocalContainerEntityManagerFactoryBean

i am not able to override the datasource that was in persistence.xml with LocalContainerEntityManagerFactoryBean.
How can I re-use same persistence.xml file for test and JEE deployments? Do we need to maintain multiple copies of persistence.xml?

persistence.xml (for both test and server deployments)

Code:

---

<persistence version="2.0" 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_2_0.xsd">
        <persistence-unit name="Jpa-SpringData">
                <jta-data-source>DS_TEST</jta-data-source>
                <class>entity.Employee</class>
        </persistence-unit>
</persistence>

---

applicationContext.xml for JUnit testing:

Code:

---

        <bean id="testDS" class="org.springframework.jdbc.datasource.DriverManagerDataSource"
                p:driverClassName="${jdbc.driverClassName}" p:url="${jdbc.url}" p:username="${jdbc.username}"
                p:password="${jdbc.password}" />
       
          <bean id="entityManagerFactory"    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
            <property name="dataSource" ref="testDS" />
            <property name="persistenceUnitName" value="Jpa-SpringData" />
            <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.OpenJpaVendorAdapter">
                <property name="showSql" value="true" />
                <property name="generateDdl" value="false" />
                <property name="database" value="ORACLE" />
            </bean>
        </property>
    </bean>

---

Any help is appreciated.

Thanks