Mapping JPA entity to more than one entityManagers with SpringBatch program - jpa

Question

I have developed SpringBatch application and deployed as Web Application in Websphere Liberty profile container. The batch program is designed to read records from a table and invokes HTTP service. Based on the service response a column named status is updated as RECORD_SENT/COMPLETE/ERROR type.
Objective is to reuse the same program for multiple datasources. The data source is passed in job parameter using client type. The datasources are in different schemas but having same datamodel.
Question: How does the transaction manager can be applied at run time inside Job Step or Tasklet?. Seeking help in this regard.
Configuration:
<bean id="entityManagerFactory1"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource1" />
<property name="persistenceUnitName" value="user" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false" />
</bean>
</property>
<property name="jpaDialect">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
</property>
</bean>
<bean id="entityManagerFactory2"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource2" />
<property name="persistenceUnitName" value="user" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false" />
</bean>
</property>
<property name="jpaDialect">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
</property>
</bean>
<bean id="entityManagerSelector" class="*com.spring.jpa.test.EntitymanagerSelector">
<property name="entityManagerFactory1" ref="entityManagerFactory1"></property>
<property name="entityManagerFactory2" ref="entityManagerFactory2"></property>
</bean>
job.xml snippet
<bean id="itemReader" class="org.springframework.batch.item.database.JpaPagingItemReader" scope="step">
<property name="entityManagerFactory" value="#{entityManagerSelector.getEntitymanagerForClient({jobParameters['client']})}" />
<property name="queryString" value="select u from User u where u.age > #{jobParameters['age']}" />
</bean>
Setting the job parameters during runtime to identify the client
JobParameters param = new JobParametersBuilder()
.addString("age", "20").addString("client", "client2")
.toJobParameters();
JobExecution execution = jobLauncher.run(job, param);

Answer 1

It will not be possible for you to set the transaction-manager of the Step/tasklet during runtime. You will be better off creating a separate Job's for each client and using their own transaction manager in the tasklet.
<bean id="transactionManager1" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory1" />
</bean>
<bean id="transactionManager2" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory2" />
</bean>
Now use these transaction manager when creating the batch job's
<job id="testJob1" xmlns="http://www.springframework.org/schema/batch">
<step id="client1step1">
<tasklet transaction-manager="transactionManager1">
<chunk reader="itemReader" writer="itemWriter" commit-interval="1" />
</tasklet>
</step>
</job>
<job id="testJob2" xmlns="http://www.springframework.org/schema/batch">
<step id="client2step2">
<tasklet transaction-manager="transactionManager2">
<chunk reader="itemReader" writer="itemWriter" commit-interval="1" />
</tasklet>
</step>
</job>
Let me know if this works out.