Starting a Java Persistence project Every EJB session
Starting a Java Persistence project Every EJB session bean needs a business interface. This isn t a special interface that needs to implement predefined methods or extend existing ones; it s plain Java. Create the following interface in the WORKDIR/src/hello package: package hello; public interface MessageHandler { public void saveMessages(); public void showMessages(); } A MessageHandler can save and show messages; it s straightforward. The actual EJB implements this business interface, which is by default considered a local interface (that is, remote EJB clients cannot call it); see listing 2.15. Listing 2.15 The Hello World EJB session bean application code package hello; import javax.ejb.Stateless; import javax.persistence.*; import java.util.List; @Stateless public class MessageHandlerBean implements MessageHandler { @PersistenceContext EntityManager em; public void saveMessages() { Message message = new Message(”Hello World”); em.persist(message); } public void showMessages() { List messages = em.createQuery(”select m from Message m . order by m.text asc”) .getResultList(); System.out.println(messages.size() + ” message(s) found:”); for (Object m : messages) { Message loadedMsg = (Message) m; System.out.println(loadedMsg.getText()); } } }
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