jpa

JPA passing list to IN clause in named native query

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The above accepted answer is not correct and led me off track for many days !! JPA and Hibernate both accept collections in native query using Query. You just need to do String nativeQuery = “Select * from A where name in :names”; //use (:names) for older versions of hibernate Query q = em.createNativeQuery(nativeQuery); q.setParameter(“names”, … Read more

JPA 2.0, Criteria API, Subqueries, In Expressions

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Below is the pseudo-code for using sub-query using Criteria API. CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder(); CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery(); Root<EMPLOYEE> from = criteriaQuery.from(EMPLOYEE.class); Path<Object> path = from.get(“compare_field”); // field to map with sub-query from.fetch(“name”); from.fetch(“id”); CriteriaQuery<Object> select = criteriaQuery.select(from); Subquery<PROJECT> subquery = criteriaQuery.subquery(PROJECT.class); Root fromProject = subquery.from(PROJECT.class); subquery.select(fromProject.get(“requiredColumnName”)); // field to map with main-query subquery.where(criteriaBuilder.and(criteriaBuilder.equal(“name”,name_value),criteriaBuilder.equal(“id”,id_value))); select.where(criteriaBuilder.in(path).value(subquery)); … Read more

kotlin data class + bean validation jsr 303

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You need to use Annotation use-site targets since the default for a property declared in the constructor is to target the annotation on the constructor parameter instead of the getter (which will be seen by JavaBeans compliant hosts) when there are multiple options available. Also using a data class might be inappropriate here (see note … Read more

java.lang.IllegalArgumentException: Removing a detached instance com.test.User#5

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EntityManager#remove() works only on entities which are managed in the current transaction/context. In your case, you’re retrieving the entity in an earlier transaction, storing it in the HTTP session and then attempting to remove it in a different transaction/context. This just won’t work. You need to check if the entity is managed by EntityManager#contains() and … Read more

Create JPA EntityManager without persistence.xml configuration file

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Is there a way to initialize the EntityManager without a persistence unit defined? You should define at least one persistence unit in the persistence.xml deployment descriptor. Can you give all the required properties to create an Entitymanager? The name attribute is required. The other attributes and elements are optional. (JPA specification). So this should be … Read more

When use getOne and findOne methods Spring Data JPA

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TL;DR T findOne(ID id) (name in the old API) / Optional<T> findById(ID id) (name in the new API) relies on EntityManager.find() that performs an entity eager loading. T getOne(ID id) relies on EntityManager.getReference() that performs an entity lazy loading. So to ensure the effective loading of the entity, invoking a method on it is required. … Read more

JPA EntityManager: Why use persist() over merge()?

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Either way will add an entity to a PersistenceContext, the difference is in what you do with the entity afterwards. Persist takes an entity instance, adds it to the context and makes that instance managed (i.e. future updates to the entity will be tracked). Merge returns the managed instance that the state was merged with. … Read more