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Manual
15

JPA Entity Fields

otherwise (e.g. by using the @Transient annotation). Storing an entity object in the database does not store methods or code. Only the persistent state of the entity object, as reflected by its persistent ... . When an entity object is stored in the database every persistent field must contain either null or a value
Manual
15

Defining a JPA Entity Class

To be able to store Point objects in the database using JPA we need to define an entity class. A JPA entity class is a POJO (Plain Old Java Object) class, i.e. an ordinary Java class that is marked (annotated) as having the ability to represent objects in the database. Conceptually this is similar
Manual
14

Database Schema Evolution

of an entity class are detected by ObjectDB. New entity objects have to be stored in the new class schema, and old entity objects, which were stored previously in the old class schema ... that enables transparent use of old entity objects after schema change. When an entity object
Manual
13

JPA Lifecycle Events

class is also invoked for entity objects of the subclasses unless that callback method is overridden ... call EntityMan­ager or Query methods and should not access any other entity objects. If a callback method ... MyListener { @PrePersist void onPrePersist(Object o) {} @PostPersist void onPostPersist(Object
Manual
13

UPDATE SET Queries in JPA/JPQL

Existing entity objects can be updated, as explained in chapter 2, by: Retrieving the entity objects into an EntityManager. Updating the relevant entity object fields within an active transaction ... an alternative way for updating entity objects. Unlike SELECT queries, which are used to retrieve data from
Forum
12

Soft Reference Object Cache Recommendation

size limit being exceeded before the post attempt.  =(  ) I desire to have my persistent objects ... objects before more recently accessed ones.  I attempted to use Java SoftReference to my large byte[] and instruct ObjectDB to use soft reference for its Level One (L1) object data cache.  I disable the L2
Manual
12

JPA Query Structure (JPQL / Criteria)

classes and objects. For example, a JPQL query can retrieve and return entity objects rather than just field values from database tables, as with SQL. That makes JPQL more object oriented friendly ... JPQL Query The following query retrieves all the Country objects in the database: SELECT c FROM
Issue
12

new objects not available in mappedBy associations

> employees;   creating a new mapped class, e.g. new Employee, won't result in this object being available in the same transaction: ie: for (Employee e : department.employee) won't include the new object ... when the object is retrieved from the database again. Try to refresh the department object
Forum
12

Speed of queries that return many objects

and tuning it could be in the range of 1-2 seconds. The overhead of preparing entity objects is more than you may expect and much slower than just reading the data from the disk. Using embedded objects or report queries (which return fields rather than entity objects) may help. If you can load the data
Forum
11

Entity listener - event instead of object

in updated entity. There is a problem however with accessing "old" version of object stored in ... @ElementCollection private Set activities; This way I can add events to given object without using EM to persist new object. What I want to accomplish is to log difference between new and old values