entitymanager

问题 I need to use multiply persistence units with different properties (in my case MySQL and Oracle database). In persistence.xml I define two different "persistence-unit"s and list only the entity classes there. Properties could be set in persitence.xml with <properties> <property name="..." value="..." /> ... Im doing it in a java class before creating the EntityManager, because I must use different properties (which I read before): EntityManagerFactory factory; ... HashMap<String, String>

问题 When I persist a "Joueur" (cf my class below), I get a NullPointerException, but I don't know why em.persist(new Joueur("pseudo", "mdp", "mail")); This is my class "Joueur" : @Entity @NamedQueries({ @NamedQuery(name = "trouverParMail", query = "SELECT * FROM Joueur j WHERE j.mail = :mail")}) public class Joueur implements Serializable { private static final long serialVersionUID = 1L; private String pseudo; private String mdp; private String mail; private Integer nbParties; private Integer

问题 I have a managedbean that has a list of entity objects of current page. after I create a new object and persist it to db using persist() in a transaction; in another transaction when I call merge(because the entity is in detached state due to previous transaction commit); entitymanager cannot find the object in persistence context and throw a select query to database. Am I missing something or is that normal behavior? Update: The above problem exists when I use mysql database and

问题 I am building a query on a generic table "Sample" and I have several types which inherit from this table "SampleOne", "SampleTwo". I require a query like : select s from Sample where s.type = :type where type would be a discriminator value of the table. Is it possible in any way ( and avoid to create an entity specific queries, one for each SampleOne, SampleTwo... etc ) I would greatly appreciate any input in this topic, Kind regards, P. 回答1: In JPA 2.0 you can use TYPE expression (though

问题 I would like to have in Java SE @Stateless public class CarDAO { @Inject private EntityManager em; public Car findById(Long id) { return em.find(Car.class, id); } } @Singleton public class Application { @Inject private CarDAO carDAO; public void run() { Car car = carDAO.findById(44); System.out.println(car); } } public class EntryPoint { public static void main(String[] args) { Application application = // missing code application.run(); } } What I have to do to achieve that? I'm using

问题 I'm using Java EE 7. I would like to know what is the proper way to inject a JPA EntityManager into an application scoped CDI bean. You can't just inject it using @PersistanceContext annotation, because EntityManager instances are not thread safe. Let's assume that we want our EntityManager to be created at the beginnig of every HTTP request processing and closed after the HTTP request is processed. Two options come into my mind: 1. Create a request scoped CDI bean which has a reference to an

问题 Am developing a JavaEE application using Netbeans.The Entity Manager is getting a null value in the application. The em is not getting injected. Still am getting a nullPointerException as em is getting a null value in createNamedQuery. Could anyone please let me know what am I missing. JSP page- index.jsp: <%@page import="managed.userBean" %> <jsp:useBean id="bean" class="managed.userBean" scope="session" /> ..... <input type="submit" value="Submit" onclick="<jsp:scriptlet> bean.validate();<

问题 Executing JPQL using hibernate 4.2.5: select c from Chargeback as cc join cc.customer as c group by c order by max(cc.created) Usecase: show customers with the latest chargbacks. produces org.hibernate.exception.SQLGrammarException: could not extract ResultSet When using select c.id from Chargeback as cc join cc.customer as c group by c order by max(cc.created) it will work. When using select c from Chargeback as cc join cc.customer as c group by c.id, c......all columns order by max(cc

问题 I'm trying to accomplish something similar to the following SQL, but using the Doctrine API. SELECT * FROM table_name WHERE column_name NOT IN (1, 2, 3); I was thinking of something like this: $entityManager->getRepository($entity)->findBy(array('ID' => array('NOT IN' => array(1, 2, 3)))); ... How far am I? 回答1: You can do this with a DQL: $result = $entityManager->createQuery("SELECT e FROM $entity e WHERE e.ID NOT IN (:ids)") ->setParameter('ids', array(1, 2, 3), \Doctrine\DBAL\Connection:

问题 I have a Java web service module and ejb modulein netbeans (All part of an enterprise application). the web service is consuming the ejb class using @EJB injection. Inside the ejb module i have a TransactionManager class which is not an enterprise bean. just a POJO class. I am trying to inject the EntityManager using @PersistanceContext(unitName = "testPU") EntityManager em; but the em is allways null. I am calling the TransactionManager class from by bean, and if i declare the EntityManager