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Database Connection using JPA

not yet exist a new database file is created. When the application is finished using ... ) and listening on the specified port (the default is 6136 when not specified). The path indicates ... of the managed entity is not affected by the rollback and is not returned to its pre-modified state. Ending

Database Schema Evolution

Modifications to entity classes that do not change their persistent field definitions (their schema ... . Fields in the new schema that do not have matching fields in the old schema are initialized with default values (0, false or null). Fields in the old schema that do not have matching fields in the new

Query Parameters in JPA

(:) followed by a valid JPQL identifier that serves as the parameter name. JPA does not provide an API ... literals rather than parameters in queries. First of all, the query is not reusable. Different ... of which are overridden in TypedQuery. That large number of methods is not typical to JPA


if setFirstResult was not applied to the query object. Returns: position of the first result Since: JPA 2 ... mode in effect for the query execution. If a flush mode has not been set for the query object ... : IllegalStateException - if the query is found not to be a Java Persistence query language SELECT query or


this API in order to work around the fact that Java generics are not compatible with varags ... Predicate isNotEmpty( Expression<C> collection) Create a predicate that tests whether a collection is not empty. Create a predicate that tests whether a collection is not empty. Parameters: collection

JPA Lifecycle Events

and any access level (public, protected, package and private) but should not be static. The annotation ... that fires the entity lifecycle event (which is still in progress) callback methods should not call EntityManager or Query methods and should not access any other entity objects. If a callback method


the database, UPDATE queries do not retrieve data from the database, but when executed, update ... with the database. For example, the EntityManager may not be aware that a cached entity object in ... name) for iteration. Multiple variables and JOIN are not supported. The SET clause defines one or

Storing JPA Entity Objects

is committed. An IllegalArgumentException is thrown by persist if the argument is not an instance ... , the referenced Address instance is not stored in the database automatically with the referencing Employee ... another entity object that is not expected to be stored in the database at the end of that transaction

Defining a JPA Entity Class

Entity Classes Storing an entity object in the database does not store methods and code ... field that is not declared as static or transient is a persistent field. For example ... supports implicit object IDs, so an explicitly defined primary key is not required. On the other hand


if a transaction is not active. If a datastore transaction is active, this method verifies the consistency ... if flush were called, but it is not required to do so. If an optimistic transaction is active, this method ... of the instance persistent, the closure of the instance is not deleted from the data store. This method

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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