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JPA Lifecycle Events

(added to the EntityManager). @PostPersist - after storing a new entity in the database (during commit or ... the database (during commit or flush). @PreRemove - when an entity is marked for removal in the EntityManager. @PostRemove - after deleting an entity from the database (during commit or flush). An entity

Database Management Settings

properly. Moving or copying a database file that has not been closed properly without its recovery file ... attribute (whose value is "true" or "false") specifies if a recovery file is used. The sync attribute (whose value is "true" or "false") specifies if physical writing is required before commit returns

Database Doctor

of the Operating System, Java or ObjectDB). Copying a database file while it is open and in use. Network or I/O failure when copying, moving or transferring a database file. Transferring a database file over FTP in ASCII mode (BINARY mode should be used). Deleting an ObjectDB database recovery file or

Database Schema Evolution

with default values (0, false or null). Fields in the old schema that do not have matching fields in the new ... and either the same type or a convertible type, as explained below. A matching field ... with a default value (0, false or null). The following type conversions are supported: From any numeric type

Comparison in JPQL and Criteria API

/ SQL Set 2 - Java / JDO Less Than < < Greater Than > > Less Than or Equal To <= <= Greater Than or ... == FALSE TRUE != TRUE FALSE Comparison operators are always evaluated to TRUE, FALSE or NULL. When both operands are not NULL (not shown in the table) the operator is evaluated to either TRUE or FALSE

Locking in JPA

that has to be updated or deleted is checked. An exception is thrown if it is found out that an update ... field. During commit (and flush), ObjectDB checks every database object that has to be updated or ... some ORM JPA providers) is defined in the entity class or not. Pessimistic Locking The main

Index Definition

. A PersistenceException is thrown on commit (or flush) if different entities have the same value in ... with no unique constraint or a unique index if unique="true"is specified (the default is false). The optional ... . When an entity object is stored in the database every indexed field must contain either null or

JPA Metamodel API

Metamodel API is Metamodel. It can be obtained either by the EntityManagerFactory's getMetamodel method or ... instance: // Get a managed type (entity, embeddable or mapped super classes): ManagedType ... to support an ID class when using multiple ID fields or properties. Finally, the EntityType interface

GROUP BY and HAVING clauses

clause. When a GROUP BY clause exists in a JPQL query, database objects (or tuples of database objects ... calculations (count, sum, avg, max, min) that are carried out on all the objects (or the object tuples) in ... clause in which all the FROM/WHERE objects (or object tuples) are considered as one group. For example


of Query for executing a named query (in the Java Persistence query language or in native SQL). Create an instance of Query for executing a named query (in the Java Persistence query language or in ... instance Throws: IllegalArgumentException - if a query has not been defined with the given name or

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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