I stumbled upon this issue as well. I would ultimately like to execute the following JPQL: SELECT COUNT(u) FROM ( SELECT DISTINCT u FROM User u JOIN u.roles r WHERE r.id IN (1) ) But this wasn’t possible, also not with criteria API. Research taught that this was just a design limitation in JPA. The … Read more
I wrote my own generator to solve the issue. public class UseExistingIdOtherwiseGenerateUsingIdentity extends IdentityGenerator { @Override public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException { Serializable id = session.getEntityPersister(null, object).getClassMetadata().getIdentifier(object, session); return id != null ? id : super.generate(session, object); } } and use it like this: (replace the package name) @Id @GenericGenerator(name = “UseExistingIdOtherwiseGenerateUsingIdentity”, … Read more
You are trying to set up a standalone JPA project. In order to do so you need a JPA provider jars. The two more popular providers are Eclipselink and Hibernate. If you are using maven you can add dependencies to their implementations. For Eclipselink <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>eclipselink</artifactId> <version>2.5.1</version> </dependency> For Hibernate <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>4.3.6.Final</version> … Read more
https://www.hibernate.org/43.html Basically, you have a few options. -You can use the “open session in view” pattern where you use a filter/interceptor/AOP – style logic to open a session when server side logic begins, and close it when it’s through. -You could implement conversations spanning several request-response cycles. A plain old Servlet Filter is the easiest.
If you’re really using the different DataSourcees in a multi-tenant kind of way (essentially assigning a request to a DataSource and sticking with it for the entire request) you should have a look at AbstractRoutingDataSource. It essentially provides a way to keep a Map of DataSourcees as well as a callback method to return a … Read more
Hibernate doesn’t allow fetching more than one bag because that would generate a Cartesian product. Now, you will find lots of answers, blog posts, videos, or other resources telling you to use a Set instead of a List for your collections. That’s terrible advice! Using Sets instead of Lists will make the MultipleBagFetchException go away, … Read more
Either use Hibernate 5.2.0+ or for earlier Hibernate 5 add the following dependency: <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-java8</artifactId> <version>${hibernate.version}</version> </dependency>
I want to use one class to map three tables, From what I know is that javax.persistance provides @SecondaryTable annotation to map two tables to one class use @SecondaryTables to map more than one table. You can map a single entity bean to several tables using the @SecondaryTables class level annotations. To express that a … Read more
In SQL the solution is very simple – join the table with a subquery, which gives you the most recent meeting for each attendee: select * from Meeting ALL join ( select max(meetingDate) as newest, attendee from Meeting group by attendee ) LATEST on ALL.meetingDate = LATEST.newest AND ALL.attendee = LATEST.attendee This works, and works … Read more
Is it possible to change the table name of an entity as follows on runtime since they have the same table structure after all? This is not really possible, at least not with standard JPA (which doesn’t mean I did it with non standard JPA) as mentioned in questions such as: In @Table(name = “tableName”) … Read more