<?xml version="1.0" encoding="UTF-8"?>
<persistence 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"
             version="2.1">
    <persistence-unit name="studentDatabase" transaction-type="JTA">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <jta-data-source>jdbc/studentDatabase</jta-data-source>
        <class>com.dcpro.entities.Group</class>
        <class>com.dcpro.entities.Student</class>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/student_database"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="root"/>
        </properties>
    </persistence-unit>
</persistence>

import com.google.inject.AbstractModule;

public class DAOModule extends AbstractModule {
    @Override
    protected void configure() {

    }
}

@Stateless
public class DAOService {

@PersistenceUnit(unitName = "studentDatabase")
private EntityManager em;

@Inject
public DAOService() {
}

@SuppressWarnings("unchecked")
public <T> List<T> getEntities(Class<T> clazz) {
    Query query = em.createQuery("select e from " + clazz.getSimpleName() + " e");
    return query.getResultList();
}
}

public class AbstractView extends VerticalLayout implements View {

    public void setEntityClass(Class entityClass) {
        this.entityClass = entityClass;
    }

    Class entityClass;

    protected DAOService daoService;

    public AbstractView() {
        Injector injector = Guice.createInjector(new DAOModule());
        daoService = injector.getInstance(DAOService.class);
    }

    @Override
    public void enter(ViewChangeListener.ViewChangeEvent event) {

    }
}

-resources
    beans.xml
    META-INF
      persistence.xml
-webapp
    META-INF
      context.xml
      MANIFEST.MF
    WEB-INF
      web.xml