Use EclipseLink JPA extensions for:

Mappings

11g provide annotations to configure advanced mapping including:

• @BasicCollection - stores a collection of simple types, such as String, Number, Date, etc., in a single table

• @BasicMap - stores a collection of key-value pairs of simple types, such as String, Number, Date, etc., in a single table

• @PrivateOwned - supports orphan management

• @JoinFetch - enables the joining and reading of a referenced object(s) in the same query as the source object

• @Mutable - indicates that the value of a complex field itself can be changed or not changed (instead of being replaced)

• @Transformation - enables the mapping of a single field to to one or more database columns.

• @VariableOneToOne - supports OneToOne mappings to an interface rather than an Entity

• @ReadOnly - makes an Entity read only

Converters

11g provides a number of new converter features including ease of configuration using JPA annotations. EclipseLink JPA converter annotations include: @Converter, @TypeConverter, @ObjectTypeConverter, @StructConverter, and @Convert. With these annotations it's easy to perform data type conversion and work with user defined types.

In the following example, a converter named Currency is defined and associated with the custom converter class CurrencyConverter. The CurrencyConverter class is responsible for converting between a database string representation of a currency (e.g., USD) and the corresponding java.util.Currency object. Annotating the Employee's salaryCurrency field with @Convert("Currency") ensures that the conversion between Currency object and database String is automatically performed when reading, writing, or updating an Employee object.

Entity Caching

11g introduces new JPA annotations for configuring Entity caching and (@Cache , @TimeOfDay) and existence checking policy (@ExistenceChecking). In the following example, the Employee Entity is configured with a HardWeak cache and an expiry policy that will invalidate all instances at 1am. Time of day expiry is useful in systems with regular datafeeds. Other expiry options are supported by the @Cache annotation. With the CHECK_DATABASE expiry policy specified, the database will be checked to see if a new object to be persisted already exists on the database.

A number of caching persistence unit properties are also available to override some entity caching annotations, define defaults, and to configure caching options not supported by annotations.

Optimistic Locking

The new @OptimisticLocking annotation supports the configuration of advanced optimistic locking policies that are especially useful when dealing with legacy database schemas that may not have a version or timestamp column. In the following example, the Employee Entity is configured with a CHANGED_COLUMNS optimistic locking policy. This policy will generate an UPDATE SQL statement that ensures that all columns being modified still have the same value as when they were read.

Stored Procedure Query

Stored procedure usage has been simplified through the @NamedStoredProcedureQuery and @NamedStoredProcedureQueries annotations. These annotations support the use of stored procedures which are encapsulated as named queries so that they are easy to use. Client code is unaware that the query they are executing is a stored procedure and not a JPQL or native SQL query

Lazy Loading

If you are developing your application in a Java EE environment, you only have to set the fetch attribute of any JPA mapping to FetchType.LAZY (unless it defaults to FetchType.LAZY). EclipseLink JPA will supply all the necessary lazy loading functionality.

If you are developing your application in a Java SE environment you can enable lazy loading support for all mapping types by configuring either dynamic or static weaving.

Schema Generation

Generation of the database schema for the Entities in a persistence unit is configured through persistence unit properties. Supported options include whether to generate the schema on the database, to file, or both, what directory to generate a files into, and whether to drop and create tables or just create.