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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship Mappings/Common Relationship Configurations/JoinFetch"
< EclipseLink | UserGuide | JPA | Basic JPA Development | Mapping | Relationship Mappings | Common Relationship Configurations
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| − | = | + | {{EclipseLink_UserGuide |
| − | + | |info=y | |
| + | |toc=n | ||
| + | |eclipselink=y | ||
| + | |eclipselinktype=JPA | ||
| − | + | |api=y | |
| + | |apis= | ||
| + | * [http://www.eclipse.org/eclipselink/api/latest/org/eclipse/persistence/annotations/JoinFetch.html @JoinFetch] | ||
| − | = | + | }} |
| + | =@JoinFetch= | ||
| − | + | Use the <tt>@JoinFetch</tt> annotation to enable the joining and reading of the related objects in the same query as the source object. | |
| + | {{EclipseLink_Note | ||
| + | |note=We recommend setting join fetching at the query level, as not all queries require joining. | ||
| + | }} | ||
| − | + | You can specify the <tt>@JoinFetch</tt> annotation for the following mappings: | |
| − | + | * <tt>@OneToOne</tt> | |
| + | * <tt>[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings/OneToMany|@OneToMany]]</tt> | ||
| + | * <tt>@ManyToOne</tt> | ||
| + | * <tt>[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings/ManyToMany|@ManyToMany]]</tt> | ||
| + | * <tt>@BasicCollection</tt> (deprecated) | ||
| + | * <tt>@BasicMap</tt> (deprecated) | ||
| − | |||
| − | + | Alternatively, you can use batch reading, especially for collection relationships.]]. | |
| − | + | {{EclipseLink_AttributeTable | |
| − | + | |caption=@JoinFetch Annotation Attributes | |
| − | + | |content=<tr> | |
| − | + | <td>'''<tt>value</tt>'''</td> | |
| − | + | <td>Set this attribute to the <tt>org.eclipse.persistence.annotations.JoinFetchType</tt> enumerated type of the fetch that you will be using. | |
| − | + | ||
| + | The following are the valid values for the <tt>JoinFetchType</tt><nowiki>:</nowiki> | ||
| + | * <tt>INNER</tt> – This option provides the inner join fetching of the related object.<br>Note: Inner joining does not allow for null or empty values. | ||
| + | * <tt>OUTER</tt> – This option provides the outer join fetching of the related object.<br>Note: Outer joining allows for null or empty values.<br> | ||
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| − | + | </td> | |
| − | + | <td><tt>JoinFetchType.INNER</tt></td> | |
| − | + | <td>No</td> | |
| − | + | </tr> | |
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| − | + | The following example shows how to use the <tt>@JoinFetch</tt> annotation to specify <tt>Employee</tt> field <tt>managedEmployees</tt>. | |
| − | + | ||
| − | + | <span id="Example: @JoinFetch Annotation"></span> | |
| − | + | ======''Example: @JoinFetch Annotation''====== | |
| − | + | <source lang="java"> | |
| − | + | @Entity | |
| − | + | public class Employee implements Serializable { | |
| − | + | ... | |
| − | + | @OneToMany(cascade=ALL, mappedBy="owner") | |
| − | + | @JoinFetch(value=OUTER) | |
| + | public Collection<Employee> getManagedEmployees() { | ||
| + | return managedEmployees; | ||
| + | } | ||
| + | ... | ||
| + | } | ||
| + | </source> | ||
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{{EclipseLink_JPA | {{EclipseLink_JPA | ||
| − | |previous= [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship_Mappings/ | + | |previous= [[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship_Mappings/Common_Relationship_Configurations|Common Relationship Configurations]] |
|next=[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings|Collection Mappings]] | |next=[[EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Relationship_Mappings/Collection_Mappings|Collection Mappings]] | ||
| − | |up=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship_Mappings/ | + | |up=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship_Mappings/Common_Relationship_Configurations|Common Relationship Configurations]] |
| + | |version=2.2.0 DRAFT}} | ||
Latest revision as of 12:07, 17 May 2011
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Key API
@JoinFetch
Use the @JoinFetch annotation to enable the joining and reading of the related objects in the same query as the source object.
Note: We recommend setting join fetching at the query level, as not all queries require joining.
You can specify the @JoinFetch annotation for the following mappings:
- @OneToOne
- @OneToMany
- @ManyToOne
- @ManyToMany
- @BasicCollection (deprecated)
- @BasicMap (deprecated)
Alternatively, you can use batch reading, especially for collection relationships.]].
| Attribute | Description | Default | Required? |
|---|---|---|---|
| value | Set this attribute to the org.eclipse.persistence.annotations.JoinFetchType enumerated type of the fetch that you will be using.
The following are the valid values for the JoinFetchType:
|
JoinFetchType.INNER | No |
The following example shows how to use the @JoinFetch annotation to specify Employee field managedEmployees.
Example: @JoinFetch Annotation
@Entity public class Employee implements Serializable { ... @OneToMany(cascade=ALL, mappedBy="owner") @JoinFetch(value=OUTER) public Collection<Employee> getManagedEmployees() { return managedEmployees; } ... }
