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Database Schema Evolution

> A matching field is a field with the same name and either the same type or a convertible type, as ... ) the fields are not considered as matching and the new field is initialized with a default ... , BigInteger, BigDecimal and enum values that are stored as numeric

JPA Persistence Unit

> in JPA (as explained in the JPA Overview section ... that is described in this manual can be replaced by equivalent XML in the mapping files (as explained below).as

ORDER BY clause (JPQL / Criteria API)

to collect as results. Then the SELECT clause builds the results by evaluating the result expressions ... > as the primary sort key and by name as the secondary sort key: SELECT c.currency AS currency, AS name FROM Country c


Queries with createQuery As with most other operations in JPA, using queries starts ... > in the following code snippets), which serves as a factory for both TypedQuery instance the expected result type has to be passed as

CRUD Database Operations with JPA

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 a managed entity

Locking in JPA

> database object, which is referenced as e1 by em1 and as e2 by ... while the transaction is active, as so: arguments for the

Auto Generated Values

numeric persistent fields as well. Several different value generation strategies can be used as ... automatic object IDs for entity objects with no primary key fields defined (as explained in ... for every new entity object. These generated values are unique at the database level and are never recycled, as

JPA Query Structure (JPQL / Criteria)

objects 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 ... elements such as names of entity classes and persistent fields, which are case sensitive. In addition

Step 2: Entity Class and Persistence Unit

> Enter guest as the package name - use  as the class name - use exactly that case sensitive class name. src folder as a parent folder, enter META-INF as a new folder name

Step 2: Entity Class and Persistence Unit

), select New > Source Folder, enter src/main/java as Folder ... >New > Class. Enter guest as the package name - use ... >Guest as the class name - use exactly that case sensitive class name