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Database Schema Evolution

and either the same type or a convertible type, as explained below. A matching field ... int to Date) the fields are not considered as matching and the new field is initialized ... that are stored as numeric ordinal values (the default). From any type to Boolean or boolean (0, null

JPA Persistence Unit

to instantiate an EntityManagerFactory in JPA (as explained in the JPA Overview section) requires ... that is described in this manual can be replaced by equivalent XML in the mapping files (as ... , username and password, as demonstrated above. XML Mapping Metadata ObjectDB supports using XML metadata

ORDER BY clause (JPQL / Criteria API)

clause produces objects for examination and the WHERE clause selects which objects to collect as results ... . The following query returns Country objects ordered by currency as the primary sort key and by name as ... above: SELECT c.currency AS currency, c.name AS name FROM Country c ORDER BY currency, name


. Building Queries with createQuery As with most other operations in JPA, using queries starts with an EntityManager (represented by em in the following code snippets), which serves as a factory ... and q2. When building a TypedQuery instance the expected result type has to be passed as an additional

CRUD Database Operations with JPA

.getTransaction().commit(); Operations that modify the content of the database (such as storing new objects) require an active transaction. In the example above, every Point object is first constructed as an ordinary Java object. It then becomes associated with an EntityManager and with its transaction (as

Locking in JPA

that manage the same Employee database object, which is referenced as e1 by em1 and as e2 by em2 (notice ... is active, as so:   em.lock(employee, LockModeType.NONE); Other Explicit Lock Modes In addition ... defines additional lock modes that can also be specified as arguments for the lock method to obtain

Auto Generated Values

this annotation for non-key numeric persistent fields as well. Several different value generation strategies can be used as explained below. The Auto Strategy ObjectDB maintains a special global ... for entity objects with no primary key fields defined (as explained in the previous section). The same

JPA Query Structure (JPQL / Criteria)

rather than just field values from database tables, as with SQL. That makes JPQL more object oriented friendly and easier to use in Java. JPQL Query Structure As with SQL, a JPQL SELECT query also consists ... elements such as names of entity classes and persistent fields, which are case sensitive. In

Step 2: Entity Class and Persistence Unit

) and selecting New > Class. Enter guest as the package name - use exactly that case sensitive package name. Enter Guest as the class name - use exactly that case sensitive class name. Click Finish ... and clicking Next). Select the project src folder as a parent folder, enter META-INF as a new folder

Step 2: Entity Class and Persistence Unit

as Folder Name and click Finish. Open the [New Java Class] dialog box, e.g. by right clicking the new source directory node (in the [Package Explorer] window) and selecting New > Class. Enter guest as the package name - use exactly that case sensitive package name. Enter Guest as the class name

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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