Mapping the same entity class to two banks

Question

Good afternoon Earthlings,

I am a beginner in java and I have the following situation. I have two databases, where I will transfer the records from one database to the other. There is the possibility of having a class of Entity mapped by the two banks?

Remarks:

• The application is using Entitymanagerfactory and the same self instancio um Entitymanger.

Answer 1

Yes. In JPA you use persistence units, which represent specific banks. If you want to specify more than one bank just declare more than one persistence unit (PU) and create the Entity managers for each of them. The persistence.xml file declaring Pus would look like this:

<persistence-unit name="pu1">
<properties>
        <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost/banco1" />
        <property name="javax.persistence.jdbc.user" value="admin" />
        <property name="javax.persistence.jdbc.password" value="123456" />

<persistence-unit name="pu2">
<properties>
        <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost/banco2" />
        <property name="javax.persistence.jdbc.user" value="admin" />
        <property name="javax.persistence.jdbc.password" value="123456" />

There to reference an entity that is in the bank 1 you only need to instantiate the pu1 in the creation of the Entity manager:

EntityManager emPU1 = Persistence.createEntityManagerFactory("pu1").createEntityManager();

For the entity that is in Bank 2 just refer to pu2:

EntityManager emPU2 = Persistence.createEntityManagerFactory("pu2").createEntityManager();

After consulting both entities, you can do your DE-PARA and persist as you wish the final result. I hope to have helped ^^