entitymanager

问题 I have a problem to understand the differences between container-managed and application-managed entity manager? I would be very grateful if you can give me an example that illustrates the differences. 回答1: For a container-managed entity manager, the container manages the life-cycle of this entity manager. For an application-managed one, the application (meaning you, the programmer) manages this. A simple but very visible difference is that you must call close() on an application-managed

问题 I have @Stateless bean which implements two interfaces (remote and local). I have also added @LocalBean anotation for accessing bean with a no-interface view. @Stateless @LocalBean public class WeatherDataBean implements WeatherDataBeanRemote, WeatherDataBeanLocal { @Inject private EntityManager entityManager; public WeatherDataBean () { } // ....attributes, getter & setter methods .... } I use @Inject for this reason taken from this example of JBoss AS7 quickstart: We use the "resource

问题 I have @Stateless bean which implements two interfaces (remote and local). I have also added @LocalBean anotation for accessing bean with a no-interface view. @Stateless @LocalBean public class WeatherDataBean implements WeatherDataBeanRemote, WeatherDataBeanLocal { @Inject private EntityManager entityManager; public WeatherDataBean () { } // ....attributes, getter & setter methods .... } I use @Inject for this reason taken from this example of JBoss AS7 quickstart: We use the "resource

问题 I am using EJB and Container managed EM ( for local testing I am creating em here). I have a requirement where I need to update database based on some condition, My issue is Update is taking very long time , how to reduce it ? I tried two approach 1> Update Query 2> Update in entity Please let me know if I am doing any mistake, or any other approach exist. Note : code for update is below public class Test { private static final int OaOnaccount = 0; private static final int ArrayList = 0;

问题 I have an entity defined as follows: public class Version { @Id private Long id; private String content; @Transient private Model model; //... } From what I can see, when a find operation is done on Entity Manager, it makes a SELECT on the underlying database only once, and then the entity is cached in the Entity Manager. However, I see that if I assign a Model to the model property, this change is not reflected to the cached entity. E.g. if in one call, a find operation is done and Model is

问题 I believe the entity that I wish to delete, is a managed entity. But, regardless, why is merging it then removing it giving me the following error: deleted instance passed to merge Someone said on stackoverflow that merge should be ignored if it is a managed entity. So why is this not being ignored? The way I wish to delete it is like so: TrialUser mergedEntity = em.merge(tu); em.remove(mergedEntity); But this errors, but if I get rid of the first line it seems to work fine. But I want it the

问题 I've built some JPA stuff in the past that used an instance of the javax.persistence.EntityManager per instance of DAO; this is the way most examples are setup. public class BaseDaoThatEveryDaoExtends { @PersistenceContext private EntityManager entityManager; } I've just stumbled upon code that uses a static javax.peristence.EntityManger injected by a PersistenceContext annotation, the architect tells me this causes no problems and they never had any problem even in a clustered application

问题 I am new to Spring MVC. I've been searching for few days for a solution to my problem, without any success. Here is my stack: jBoss 4.2.3GA server I know it's a very old version, but that is what I am limited to right now. jBoss 7.1 will be approved for use in my organization within the next few months, but I would like to make my R&D application work in the 4.2.3GA server. That means I have added all required jars in my /lib folder. Spring MVC 4.0.2 EJB3.0 / JPA for persistence DBMS is

问题 I'm using Spring 3.1.1.RELEASE, Hibernate 4.1.0.Final, JUnit 4.8, and JPA 2.0 (hibernate-jpa-2.0-api). I'm trying to write a query and search based on fields of member fields. What I mean is I have this entity … @GenericGenerator(name = "uuid-strategy", strategy = "uuid.hex") @Entity @Table(name = "cb_organization", uniqueConstraints = {@UniqueConstraint(columnNames={"organization_id"})}) public class Organization implements Serializable { @Id @NotNull @GeneratedValue(generator = "uuid

问题 I am currently trying to figure out the best way to get a entity manager and a usertransaction in my application. In JBoss 5.1 I was able to inject it directly into the JSP file, but this is not permitted anymore: <%!@PersistenceContext(unitName = "unitname") public EntityManager em; @Resource UserTransaction utx; %> I have to access em and utx from different locations in my application such as Servlets and Controller classes. So it would be great to have it in one place and to access it