Module eclipselink
Package org.eclipse.persistence.annotations

Annotation Interface FetchGroup

@Target(TYPE) @Retention(RUNTIME) @Repeatable(FetchGroups.class) public @interface FetchGroup
A fetch group is a performance enhancement that allows a group of attributes of an object to be loaded on demand, which means that the data for an attribute might not load from the underlying data source until an explicit access call for the attribute first occurs. It avoids the wasteful practice of loading up all data of the object's attributes, in which the user is interested in only partial of them.

A great deal of caution and careful system use case analysis should be use when using the fetch group feature, as the extra round-trip would well offset the gain from the deferred loading in many cases.

EclipseLink fetch group support is twofold: the pre-defined fetch groups at the Entity or MappedSuperclass level; and dynamic (use case) fetch groups at the query level.

Fetch groups can only be used when weaving is enabled or when individual classes that define them explicitly implement the FetchGroupTracker interface.

Author:
Guy Pelletier

  • Required Element Summary

    Required Elements
    Modifier and Type
    Required Element
    Description
    FetchAttribute[]
    attributes
    The list of attributes to fetch.
    String
    name
    The fetch group name.

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    boolean
    load
    Indicates whether all relationship attributes specified in the fetch group should be loaded.

  • Element Details

    • name

      String name
      The fetch group name.

    • load

      boolean load
      Indicates whether all relationship attributes specified in the fetch group should be loaded.
      Default:
      false

    • attributes

      FetchAttribute[] attributes
      The list of attributes to fetch.