@Transactional

The demo application used is mentioned how to present use a REST API to execute CRUD operations against a back-end db. For the demo’s sake I’ll say a client of the REST API also needs resources from a “btrs” system – where it needs to combine them with the ones from the actual system and present them to their users.

For that I will implement two new two beans for the entity manager, transaction manger and datasource will use the same data access layer to highlight the use of multiple data sources.

Now let’s see how to configure and code multiple data sources with Spring and JPA:

In the Spring application contex:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee" xmlns:util="http://www.springframework.org/schema/util"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:security="http://www.springframework.org/schema/security"
    xmlns:task="http://www.springframework.org/schema/task" xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
            http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
            http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd
            http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd
            http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
            http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.0.xsd
            http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-4.0.xsd">

    <context:annotation-config />
    <tx:annotation-driven />
    <task:annotation-driven executor="executor" />
    <task:executor id="executor" pool-size="1" />

    <bean id="properties"
        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="WEB-INF/system.properties" />
    </bean>

    <!-- DATABASE SETUP -->

    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="username" value="postgres" />
        <property name="password" value="1234" />
        <property name="driverClassName" value="org.postgresql.Driver" />
        <property name="url" value="jdbc:postgresql://localhost:5432/btrs2" />
    </bean>

    <bean id="dataSourceAttendance" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="username" value="postgres" />
        <property name="password" value="1234" />
        <property name="driverClassName" value="org.postgresql.Driver" />
        <property name="url" value="jdbc:postgresql://localhost:5432/demo2" />
    </bean>

    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="persistenceUnitName" value="btrsPU" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="generateDdl" value="true" />
                <property name="showSql" value="true" />
                <property name="databasePlatform" value="org.hibernate.dialect.PostgreSQLDialect" />
            </bean>
        </property>
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">create</prop>
            </props>
        </property>
    </bean>

    <bean id="entityManagerFactoryAttendance"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSourceAttendance" />
        <property name="persistenceUnitName" value="attendancePU" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="generateDdl" value="true" />
                <property name="showSql" value="true" />
                <property name="databasePlatform" value="org.hibernate.dialect.PostgreSQLDialect" />
            </bean>
        </property>
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">validate</prop>
            </props>
        </property>
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
        <!-- <qualifier value="btrs"/> -->
    </bean>

    <bean id="transactionManagerAttendance" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactoryAttendance" />
        <!-- <qualifier value="attendance"/> -->
    </bean>
</beans>