Java Persistence API (JPA) Extensions Reference for EclipseLink,
Release 2.4 |
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Use @ExistenceChecking to specify how EclipseLink should check to determine if an entity is new or exists.
On merge() operations, use @ExistenceChecking to specify if EclipseLink uses only the cache to determine if an object exists, or if the object should be read (from the database or cache). By default the object will be read from the database.
Annotation Elements
Table 2-20 describes this annotation's elements.
Table 2-20 @ExistenceChecking Annotation Elements
| Annotation Element | Description | Default |
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(Optional) Set the existence checking type:
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Usage
You can specify @ExistenceChecking on an Entity or MappedSuperclass.
EclipseLink supports the following existence checking types:
ASSUME_EXISTENCE – If the object's primary key does not include null then it must exist. You may use this option if the application guarantees or does not care about the existence check.
ASSUME_NON_EXISTENCE – Assume that the object does not exist. You may use this option if the application guarantees or does not care about the existence check. This will always force an INSERT operation.
CHECK_CHACHE – If the object's primary key does not include null and it is in the cache, then it must exist.
CHECK_DATABASE – Perform a SELECT on the database.
Examples
Example 2-41 shows how to use this annotation.
Example 2-41 Using @ExistenceChecking Annotation
@Entity
@Cache(type=CacheType.HARD_WEAK, expiryTimeOfDay=@TimeOfDay(hour=1))
@ExistenceChecking(ExistenceType.CHECK_DATABASE)
public class Employee implements Serializable {
...
}
See Also
For more information, see:
"Enhancing Performance" in Solutions Guide for EclispeLink
