@Table is optional. @Entity is needed for annotating a POJO class as an entity, but the name attribute is not mandatory. If you have a class @Entity class MyEntity {} A table with name “MyEntity” will be created and the Entity name will be MyEntity. Your JPQL query would be: select * from MyEntity In … Read more
These 2 links help me understand the inheritance concept the most: http://docs.oracle.com/javaee/6/tutorial/doc/bnbqn.html http://www.javaworld.com/javaworld/jw-01-2008/jw-01-jpa1.html?page=6 To understand discriminator, first you must understand the inheritance strategies: SINGLE_TABLE, JOINED, TABLE_PER_CLASS. Discriminator is commonly used in SINGLE_TABLE inheritance because you need a column to identify the type of the record. Example: You have a class Student and 2 sub-classes: GoodStudent … Read more
You need to convert the enum to and from the raw value. In Swift 1.2 (Xcode 6.3), this would look like this: class AppState : NSObject, NSCoding { var idx = 0 var stage = Stage.DisplayAll override init() {} required init(coder aDecoder: NSCoder) { self.idx = aDecoder.decodeIntegerForKey( “idx” ) self.stage = Stage(rawValue: (aDecoder.decodeObjectForKey( “stage” ) … Read more
As someone who developed a scientific project that went from using folders of files to HDF5, I think I can shed some light on the advantages of HDF5. When I began my project, I was operating on small test datasets, and producing small amounts of output, in the range of kilobytes. I began with the … Read more
Use the default data dir, which is /prometheus. To do that, use this line instead of what you have in your command: … –volume a-new-volume:/prometheus \ … Found here: https://github.com/prometheus/prometheus/blob/master/Dockerfile Surprisingly is not mentioned in the image docs
If it’s really dictionary like arbitrary data you’re looking for you can probably use a two-level setup with one model that’s a container and another model that’s key-value pairs. You’d create an instance of the container, create each of the key-value instances, and associate the set of key-value instances with the container instance. Something like: … Read more
As mentioned in an answer to a similar question, since v3.1.0 this is a supported feature of ProtocolBuffers. For Java, include the extension module com.google.protobuf:protobuf-java-util and use JsonFormat like so: JsonFormat.parser().ignoringUnknownFields().merge(json, yourObjectBuilder); YourObject value = yourObjectBuilder.build();
It depends how you obtained it. If you created it using EntityManagerFactory you will have to close it no matter what framework you use. If you obtained it using dependency injection (eg using EJB and @PersistenceContext annotation) you should not close it by hand (AFAIK it will cause RuntimeException).
I agree with much of what you say. One thing I’d like to append, though, about the persistence of enums: I don’t believe the generation of the enums at build time from the DB values is acceptable, but I also think that the runtime check is not a good solution. I’d define a third means: … Read more
Define limit and offset on the Query: return em.createQuery(query) .setFirstResult(offset) // offset .setMaxResults(limit) // limit .getResultList(); From the documentation: TypedQuery setFirstResult(int startPosition) Set the position of the first result to retrieve. Parameters: startPosition – position of the first result, numbered from 0 TypedQuery setMaxResults(int maxResult) Set the maximum number of results to retrieve.