How can I connect to two different databases, one for reading and one for writing in the same application using Spring? - spring

Question

Use Case: I am running a spring application which has orders. I can create plans for these orders. My dev environment/db does not have any orders and they come from a different application (we share the same db). So, Is there a way I can read orders from production database but when I create a plan, it gets saved to dev database?
My persistence.xml is as below
<?xml version="1.0" encoding="UTF-8" ?>
<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_2_0.xsd"
version="2.0">
<persistence-unit name="Demo_PU" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.entity.ErrorMessage</class>
<class>com.entity.ErrorMessageTxt</class>
<class>com.entity.ErrorMessageTxtId</class>
<class>com.entity.Language</class>
<class>com.entity.TextEntity</class>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.InformixDialect" />
<property name="hibernate.show_sql" value="false" />
<property name="hibernate.format_sql" value="true" />
<property name="hibernate.id.new_generator_mappings" value="true" />
<property name="hibernate.cache.region.factory_class"
value="net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory" />
<property name="hibernate.cache.use_second_level_cache"
value="true" />
<property name="hibernate.cache.use_query_cache" value="true" />
<property name="hibernate.generate_statistics" value="false" />
<property name="hibernate.connection.useUnicode" value="true" />
<property name="hibernate.connection.characterEncoding"
value="UTF-8" />
<!-- Adding timeouts for Lock Mode and Query -->
<property name="javax.persistence.query.timeout" value="60000" />
<property name="javax.persistence.lock.timeout" value="60000" />
</properties>
</persistence-unit>
</persistence>
My spring-config.xml is as below
<?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"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:task="http://www.springframework.org/schema/task"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-3.0.xsd">
<context:component-scan base-package="com.project"/>
<context:component-scan base-package="com.project2"/>
<task:annotation-driven executor="myExecutor" scheduler="myScheduler"/>
<task:executor id="myExecutor"/>
<task:scheduler id="myScheduler"/>
<bean id="qa-informix" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc/dcSysCommon"/>
</bean>
<bean id="pum" class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
<property name="persistenceXmlLocations">
<list>
<value>classpath*:META-INF/persistence.xml</value>
</list>
</property>
<property name="dataSources">
<map>
<entry key="localDataSource" value-ref="qa-informix" />
</map>
</property>
<property name="defaultDataSource" ref="qa-informix"/>
</bean>
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitManager" ref="pum" />
<property name="jpaDialect">
<bean class="com.project.utils.IsolationSupportHibernateJpaDialect"/>
</property>
<property name="persistenceUnitName" value="PYD_PU" />
</bean>
<!-- bean post-processor for JPA annotations -->
<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
<!-- this enables the configuration of transactional behavior based on annotations -->
<tx:annotation-driven transaction-manager="txManager"/>
<bean id="txManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="emf" />
</bean>
<bean id="interpolator" class="org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator" />
<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
<property name="messageInterpolator" ref="interpolator" />
</bean>
<bean class="com.project3.common.core.bo.LanguageBusinessObject" primary="true" />
<bean name="restUtils" class="com.project1.utils.RestUtils" />
<bean id="srvPropertyFile" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="srvPropertyFile" />
</bean>
<bean id="beanConfig" class="io.swagger.jaxrs.config.BeanConfig">
<property name="title" value="Swagger UI for QAS"/>
<property name="version" value="1.0.0" />
<property name="schemes" value="http" />
<property name="host" value="#{srvPropertyFile.hostName}:#{srvPropertyFile.pydPort}" />
<property name="basePath" value="planyourday/#{srvPropertyFile.countryCode}/#{srvPropertyFile.dcNumber}"/>
<property name="resourcePackage" value="com.project1.resources"/>
<property name="license" value="Apache 2.0 License"/>
<property name="licenseUrl" value="http://www.apache.org/licenses/LICENSE-2.0.html"/>
<property name="scan" value="true"/>
</bean>
<bean id="apiListingResource" class="com.project1.utils.SwaggerApiListingResource"/>
<bean id="swaggerSerializers" class="io.swagger.jaxrs.listing.SwaggerSerializers" scope="singleton"/>
</beans>
In my Jetty server config, I am defining the srvPropertyFile which references to the environment.properties file which has the database connection to dev db.
How should I manage my persistence context so that the entity manager used while reading orders and the entity manager used while creating plans connects to different databases?

Answer 1

you have to configure two persistence unit, data source and transaction manager(one for read and other for write) each.
While using entity manager specify the persistence unit like below.
PersistenceUnit(unitName = "x")
EntityManagerFactory entityManagerFactory;