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Latest revision as of 11:14, 25 April 2012

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Examples

Locking

Locking

This section describes choices you need to make when deciding on how to use EclipseLink locking options in your application architecture. We strongly recommend always using a locking policy in a concurrent system.

These choices can be summarized as follows:

Optimistic Locking
Pessimistic Locking

If you are building a three-tier application, be aware of how that architecture affects the way you use locking).

Version: 2.2.0 DRAFT
Other versions...

Many-to-Many Mapping	Mapping	Optimistic Locking
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Retrieved from "https://wiki.eclipse.org/index.php?title=EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Locking&oldid=299640"

@@ Line 1: / Line 1: @@
-=Locking=
+{{EclipseLink_UserGuide
-You have the choice between optimistic and pessimistic locking. We recommend using EclipseLink [[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Locking/Optimistic_Locking|optimistic locking]].
+|info=y
+|toc=n
-By default, EclipseLink persistence provider assumes that the application is responsible for data consistency.
+|eclipselink=y
+|eclipselinktype=JPA
-Use the <tt>@Version</tt> annotation to enable the JPA-managed optimistic locking by specifying the version field or property of an entity class that serves as its optimistic lock value (recommended).
+|examples=y
+|example = *[[EclipseLink/Examples/JPA/Locking|Locking]]
-When choosing a version field or property, ensure that the following is true:
-* there is only one version field or property per entity;
-* you choose a property or field persisted to the primary table (see Section 9.1.1 "Table Annotation" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification]);
-* your application does not modify the version property or field.
-{{EclipseLink_Note
-|note=The field or property type must either be a numeric type (such as <tt>Number</tt>, <tt>long</tt>, <tt>int</tt>, <tt>BigDecimal</tt>, and so on), or a <tt>java.sql.Timestamp</tt>. We recommend using a numeric type.
 }}
+=Locking=
+This section describes choices you need to make when deciding on how to use EclipseLink locking options in your application architecture. We strongly recommend always using a locking policy in a concurrent system.
-The <tt>@Version</tt> annotation does not have attributes.
+These choices can be summarized as follows:
+* [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Locking/Optimistic Locking|Optimistic Locking]]
-The [[#Example 18-10|Usage of @Version Annotation]] example shows how to use this annotation to specify property <tt>getVersionNum</tt> as the optimistic lock value. In this example, the column name for this property is set to <tt>OPTLOCK</tt> (see Section 9.1.5 "Column Annotation" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification]) instead of the default column name for the property.
+* Pessimistic Locking
-<span id="Example 18-10"></span>
-''''' Usage of @Version Annotation'''''
-<source lang="java">
- @Entity
- public class Employee implements Serializable {
-     ...
-     @Version
-     @Column(name="OPTLOCK")
-     protected int getVersionNum() {
-         return versionNum;
-     }
-     ...
- }
-</source>
-The <tt>@Version</tt> annotation supports the use of EclipseLink converters (see [[Using%20EclipseLink%20JPA%20Extensions%20(ELUG)#Using EclipseLink JPA Converters|Using EclipseLink JPA Converters]]).
-For more information, see the following:
+If you are building a three-tier application, be aware of how that architecture affects the way you use locking).
-* Section 3.4 "Optimistic Locking and Concurrency" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification]
-* Section 9.1.17 "Version Annotation" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification]
-* [[Using%20EclipseLink%20JPA%20Extensions%20(ELUG)#Using EclipseLink JPA Extensions for Optimistic Locking|Using EclipseLink JPA Extensions for Optimistic Locking]]
-For more information on the EclipseLink artifacts configured by these JPA metadata, refer to [[Introduction%20to%20Descriptors%20(ELUG)#Descriptors and Locking|Descriptors and Locking]].
 {{EclipseLink_JPA
-|previous= [[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings/ManyToMany|ManyToMany]]
+|previous= [[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings/ManyToMany|Many-to-Many Mapping]]
 |next=[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Locking/Optimistic Locking|Optimistic Locking]]
-|up=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping|Mapping]]}}
+|up=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping|Mapping]]
+|version=2.2.0 DRAFT}}

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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Locking"

Latest revision as of 11:14, 25 April 2012

Locking