Beginning Java EE 6 with GlassFish 3, Second Edition

CHAPTER 4 ■ MANAGING PERSISTENT OBJECTSFlushModeType getFlushMode();void lock(Object entity, LockModeType lockMode);void lock(Object entity, LockModeType lockMode, Map properties);LockModeType getLockMode(Object entity);void refresh(Object entity);void refresh(Object entity, LockModeType lockMode);void refresh(Object entity, Map properties);void refresh(Object entity, LockModeType lockMode, Map properties);void clear();void detach(Object entity);boolean contains(Object entity);Map getProperties();void setProperty(String propertyName, Object value);Query createQuery(String qlString);Query createNamedQuery(String name);Query createNativeQuery(String sqlString);Query createNativeQuery(String sqlString, Class resultClass);Query createNativeQuery(String sqlString, String resultSetMapping); TypedQuery createQuery(CriteriaQuery criteriaQuery); TypedQuery createQuery(String qlString,Class resultClass); TypedQuery createNamedQuery(String name,Class resultClass);CriteriaBuilder getCriteriaBuilder();Metamodel getMetamodel();void joinTransaction(); T unwrap(Class cls);Object getDelegate();}QueryBuilder getQueryBuilder();Don’t get scared by the API in Listing 4-4, as this chapter will cover most of the methods. In the nextsection, I explain how to get an instance of an EntityManager.Obtaining an Entity ManagerThe entity manager is the central interface to interact with entities, but it first has to be obtained by anapplication. Depending on whether it is a container-managed environment (like you’ll see in Chapter 6with EJBs) or application-managed environment, the code can be quite different. For example, in acontainer-managed environment, the transactions are managed by the container. That means you don’tneed to explicitly write the commit or rollback, which you have to do in an application-managedenvironment.128