I want to make unidirectional relation in the parent entity, Child entities have FK from the parent entity. The Name table has FK from the person table. But I just want to define the relation in person entity only. I used @JoinColumn for mapping and set name as id from the person table In the next example, I …
Tag: orm
JOOQ: How to resolve foreign keys as objects?
Say I have a table that references another table, in this case “TestScenarios” references “TestSchemas”. So each TestScenario HAS-A TestSchema. I autogenerated DAOs, however, when fetching TestScenario instance via the DAO the TestSchema field is an integer, not a TestSchema-object. Ho…
What is the purpose of the Hibernate ReturningWork interface?
I am working on one JAVA + Hibernate project but currently, I saw one interface in my code (i.e. ReturningWork<Long>) which has one method called execute(java.sql.Connection). My question is what is the use of this ReturningWork interface? Answer As I explained in more details on my blog, you can use th…
How to remove child objects from a @ManyToMany relation with lots of children in JPA and Hibernate
Let’s say I have two entities: Organization and User. Every user can be a member of many organizations and every organization can have many users. Now, I want to remove an organization (let’s say it has 1000 members). When the user has few organizations, this code is ok: But when organization coun…
Android Room Persistence Library : What is the best way to implement a many to many relation?
I used to use Realm and I am currently testing Room in order to compare both tools. I am trying to implement the following many to many relation : Here my Entity classes : The Person : @Entity(…
What is the solution for the N+1 issue in JPA and Hibernate?
I understand that the N+1 problem is where one query is executed to fetch N records and N queries to fetch some relational records. But how can it be avoided in Hibernate?
How to map an immutable collection with JPA and Hibernate
I am using JPA 2.1 and Hibernate as a JPA implementation, and I want to load a relationship as an immutable collection. Let’s take an example of an Employer parent entity that has an employees child collection. What can be done to instruct JPA to load an immutable employees collection? Answer You can us…
How to specify a Primary Key on @ElementCollection
So, there is that behavior with innodb that can cause problem if some tables lack of primary key. So with Hibernate, I am looking for a key to specifies a primary key on a @ElementCollection table with a Set as the underling data structure. I found a way to have a primary key with a map, but it is kind
MySQL to Hibernate datatype mapping for type “YEAR”
There’s a column in our database which needs to be of type YEAR. What is the corresponding Hibernate mapping for the entity? Tried searching all over, but unable to find the details. I am not sure if I need to use anything from @Temporal or any other specific type. We are using Hibernate ORM v4.1.7. Ans…
HibernateException: Couldn’t obtain transaction-synchronized Session for current thread
I’m getting the following exception when trying to use my @Service annotated classes: The way I initialize my application is complicated so I need to provide a link to the full base code to get additional information: https://github.com/dtrunk90/webapp-base. I’m using this as a maven overlay. And …