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Retrieving JPA Entity Objects

The Java Persistence API (JPA) provides various ways to retrieve objects from the database. The retrieval of objects does not require an active transaction because it does not change the content of the database. The persistence context serves as a cache of retrieved entity objects. If a requested

Left join fetch behaviour doesn't retrieve children?

();         em.clear();         em.close();         // Try to retrieve parent and children using ... is now closed, let's check if children are retrieved         em.close();         emf.close ... ();   em.close();   // Try to retrieve parent and children using left join fetch   em = emf

Bug: ClassCastException by retrieval

("find by retrieval : %s %n",tn3.getTa()); System.out.printf("Arrays : %s %n",Arrays.toString(tn3 ... , l, l, o, W, o, r, l, d, 2] find by retrieval : H Arrays : [H, e, l, l, o, W, o, r, l, d, 2 ... the ObjectDB stores temporary setting for each class. Sometimes I create and retrieve generic arrays ok

Retrieve data of all entity classes in a single query

etc) This is the code I use to retrieve all Managed Types and data for the Athlete class Metamodel ... Zazopoulos You can retrieve all the entity objects using a query on Object:     SELECT o FROM Object o ... you will have to check object types using instanceof. Alternatively, you may avoid casting and retrieve

CRUD Database Operations with JPA

it to store, retrieve, update and delete database objects. Storing New Entity Objects The following ... a Double object reflecting the average x value of all the Point objects in the database. Retrieving Existing Entities The Retrieving Entities section in chapter 3 describes several methods for retrieving

Shared (L2) Entity Cache

that it manages. The persistence context serves as a first level cache. An attempt to retrieve ... automatically: On retrieval - shared cache is used for entity objects that are not in the persistence context. If an entity object is not available also in the shared cache - it is retrieved from


Method javax.jdo.PersistenceManager void retrieve( Object pc ) Retrieve field values of an instance ... , and its field values must be retrieved. The PersistenceManager might use policy information about the class to retrieve associated instances. Parameters: pc - the instance Since: JDO 1.0

retrieve(pc, useFetchPlan)

Method javax.jdo.PersistenceManager void retrieve( Object pc, boolean useFetchPlan ) Retrieve field ... intends to use the instance, and its field values must be retrieved. If the useFetchPlan parameter ... the current fetch plan to determine which fields to load and which instances to retrieve. Since: JDO 2.0

[ODB1] Chapter 6 - Persistent Objects

or queried directly (an embedded object can only be retrieved using a reference from its containing ... in object retrieval, as shown in the next section (section 6.3). ObjectDB supports two identifying ... can easily start from them, as explained in the next section. 6.3 Retrieving Persistent Objects

[ODB1] Chapter 7 - JDOQL Queries

There are various ways to retrieve objects from an ObjectDB database, as shown in section 6.3. An Extent, for instance, can be used to retrieve all the instances of a specified persistent class. When a more selective retrieval is needed, JDOQL (JDO Query Language) is used. JDOQL for JDO is like SQL

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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