Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Overview of Using Fetch Plans and Entity Graphs

Entity graphs are templates for a particular Persistence query or operation. They are used when creating fetch plans, or groups of persistent fields that are retrieved at the same time. Application developers use fetch plans to group together related persistent fields to improve runtime performance.

By default, entity fields or properties are fetched lazily. Developers specify fields or properties as part of a fetch plan, and the persistence provider will fetch them eagerly.

For example, an email application that stores messages as `EmailMessage` entities prioritizes fetching some fields over others. The sender, subject, and date will be viewed the most often, in mailbox views and when the message is displayed. The `EmailMessage` entity has a collection of related `EmailAttachment` entities. For performance reasons the attachments should not be fetched until they are needed, but the file names of the attachment are important. A developer working on this application might make a fetch plan that eagerly fetches the important fields from `EmailMessage` and `EmailAttachment` while fetching the lower priority data lazily.

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