nie dawało mi spokoju,
więc:
persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="JavaEnterpriseApplication-warPU" transaction-type="RESOURCE_LOCAL">
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties>
<property name="javax.persistence.schema-generation.database.action" value="create" />
</properties>
</persistence-unit>
</persistence>
i w kodzie aplikacji
Map properties = new HashMap();
properties.put("javax.persistence.jdbc.driver", "org.postgresql.Driver");
properties.put("javax.persistence.transactionType", "RESOURCE_LOCAL");
properties.put("javax.persistence.jdbc.url", "jdbc//hostname:5432/database");
properties.put("javax.persistence.jdbc.user", "db_user");
properties.put("javax.persistence.jdbc.password", "bd_user_pass");
EntityManagerFactory client_emf = Persistence.createEntityManagerFactory("JavaEnterpriseApplication-warPU", properties);
EntityManager client_em = client_emf.createEntityManager();