I'm learning how to use JPA with NetBeans/Glassfish.
I have created a new EE project, and some entities in the EJB. I also created a new database. While creating the entities I also created a new persistence unit. In Data Source I chosed "New data source", and for the database connection I used the one I've created just before.
But when I look in services to my database, I don't see any table corresponding to the entities. What should I do now?
Thanks for your help. And sorry if the question is obvious but I'm really new to this kind of programming.
JPA (2.1) allows you to create the schema appropriate for your JPA entities in your persistence-unit when the EntityManagerFactory is created. The linked page tells you what persistence properties to specify in your persistence-unit for this to happen automatically. (assuming your JPA implementation is for JPA version 2.1)
Related
I'm working in a project where I'm supposed to read data from a database, called EBS, send it to the front-end and use it alongside other data to persist in another database. Let call it CPP.
The EBS must be read-only. Nothing should be persisted there. And they want all the specific queries to be stored in a xml file. For now, it's stored in the orm.xml.
I tried this solution, but it ended up creating a new table in the EBS and nothing was returned from CPP.
My questions are:
1 - How do a specify those native queries in orm.xml should be run in the EBS datasource? The datasource of CPP is in the application.properties file.
2 - Is it possible to JPA not create table with the #Entity annotation? Every time I use that, JPA ends up creating another table in the EBS. If not, is it possible to map the query directly to a POJO?
I would appreciate a solution based on JpaRepository. Thanks in advance.
There can be multiple persistence-unit in persistence.xml file but the name of those persistence units should be different .
If you don't want the entities to be created automatically then use application-managed entity manager
refter JPA application-managed entity manager
I'm trying to migrate an application from Hibernate 3.4.0.GA to Hibernate 5.1, and after complete the required changes on java code, when I deploy the application I'm watching how Hibernate is trying to create HT_ tables (global temporary), one for each #Inheritance annotated entity.
Searching on Google I've found why the tables are being created.
But in my case we are not allow to change de database to add new tables.
My Inheritance model only has one level of Inheritance and its simple, example
Does anyone knows any alternative representation for a hierarchical table structure that I can use to avoid the HT_ tables creation, or some Hibernate configuration to archive the same purpose?.
I can change the inheritance hierarchy on our entities or the Hibernate configuration. I can also asume an exception on deploy caused by the non creation of the tables if it´s non blocking for the rest of the deploy.
Thank you in advance.
UPDATE 1: New info from Hibernate official forum.
UPDATE 2: The Bug was fixed
UPDATE 3: A blog entry explaining different bulk Strategies related to the issue
As in update one on this link is more info from Hibernate official forum with a possible solution.
UPDATE: Link with the solution
If you use Oracle Database with Spring and not sure where to define property for hibernate can do the following.
Add
spring.jpa.properties.hibernate.hql.bulk_id_strategy: org.hibernate.hql.spi.id.inline.InlineIdsInClauseBulkIdStrategy
In application.yml file from resource folder.
I am working on a Java project for the university and I am trying to learn about framework, technologies and best practices for creating a well structured software that follows software engineering principles. I decided to use Spring (Spring-data-jpa), and Hibernate for the standalone software and now I am having some trouble in understanding how to use the Java Persistence Api to create an abstraction layer above the Hibernate implementation provider. What I am trying to figure out is in which part (configuration file or java class) I can switch from an ORM tool to another one. I saw that I have to use the persistence.xml file to specify the persistence unit and persistence context and also the DB parameters, but it's not clear how the EntityManager bind itself with the underlying ORM tool and in which properties this bind is set. Is the "provider" properties inside persistence.xml file that create this binding? Any link/references/examples or guide will be appreciated, thanks in advance and excuse me for my english ;)
Each persistence unit in he persistence.xml file is associated to a provider. For example, with Hibernate:
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
If you want to use another provider, you'll specify another value for this element.
Note that this is usually unnecessary, because you typically use only one provider in an application. If a single provider is available in the classpath, JPA will use that one. So switching from Hibernate to EclipseLink for example just consists in having the EclipseLink jars in the classpath rather than the Hibernate jars.
Hibernate works on the JPA API so you don't have to explicitly configure JPA if you are using hibernate. The ORM integration happens in the DAO "Data Access Object" layer of your application.
I trying to use EclipseLink JPA provider with H2 DBMS in Eclipse IDE.
When I create a new JPA project and fill the data (URL="jdbc:h2:~/test",Username="user",password="") connection type : resource local (I'm using the embedded mode)
I get 2 odd things :
when I try to create Entities from table I get a blank table list
I get an error message near #Entity notation saying that "catalog User can't be resolved for entity e1" or "Schema User can't be resolved for entity e1" depending on keeping the default value for catalog or changing it upon project creation where User is the database user name
The database already contains tables using the h2 console in Firefox
What is the cause of these problems and how can I solve it and do you have any page or book that can help with persistence.xml file (other than the oracle official web site)?
EclipseLink doesn't create the database tables for you, unless you explicitely tell it to do so.
The way to do that is described in the documentation
EclipseLink can be used to automatically generate the tables and database schema for a persistence unit. This is done through the "eclipselink.ddl-generation" persistence unit property, set to either "create-tables" or "drop-and-create-tables". The tables and constraints will be generated for all of the classes defined in that persistence unit.
The trick was to set the right catalog when creating the JPA Project and then every thing worked splendidly
Is there a java framework which given a class with data members (including objects like arraylists) will create a table in a given database and be able to insert and select these entities from said database? I know about ORMs which given a table and DTO can map rows to entities, but is there a framework which will create the tables for you as well?
Comparing two of the most popular open source persistence frameworks, iBATIS and Hibernate by RedHat. We have something called Java Persistence API (JPA) and JPA2 by Sun-Oracle.
JPA itself has features that will make up for a standard ORM framework. That said you can use JPA alone in a project.
Hibernate is the most popular ORM framework, once the JPA got introduced hibernate conforms to the JPA specifications. Apart from the basic set of specification that it should follow hibernate provides whole lot of additional stuff.