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| <p><a id="BABGBIEE" name="BABGBIEE"></a></p> |
| <div class="sect2"><!-- infolevel="all" infotype="General" --> |
| <h1>Entity</h1> |
| <p><a id="sthref55" name="sthref55"></a><a id="sthref56" name="sthref56"></a><a id="sthref57" name="sthref57"></a><a id="sthref58" name="sthref58"></a>An <span class="bold">Entity</span> is a persistent domain object.</p> |
| <p>An entity <span class="italic">can be</span>:</p> |
| <ul> |
| <li> |
| <p>Abstract or concrete classes. Entities may also extend non-entity classes as well as entity classes, and non-entity classes may extend entity classes.</p> |
| </li> |
| </ul> |
| <p>An entity <span class="italic">must have</span>:</p> |
| <ul> |
| <li> |
| <p>A no-arg constructor (public or protected); the entity class may have other constructors as well.</p> |
| </li> |
| </ul> |
| <p><a id="sthref59" name="sthref59"></a><a id="sthref60" name="sthref60"></a><a id="sthref61" name="sthref61"></a>Each persistent entity must be mapped to a database table and contain a primary key. Persistent entities are identified by the <code>@Entity</code> annotation.</p> |
| <p>Use this procedure to add persistence to an existing entity:</p> |
| <ol start="1"> |
| <li> |
| <p>Open the Java class in the <span class="gui-object-title">Package Explorer.</span></p> |
| </li> |
| <li> |
| <p>Select the class in the JPA Structure view.</p> |
| </li> |
| <li> |
| <p>In the JPA Details view, click the mapping type hyperlink to access the Mapping Type Selection dialog. In the following figure, clicking <span class="italic">entity</span> invokes the dialog from the JPA Details View.</p> |
| <div class="figure"><a id="sthref62" name="sthref62"></a> |
| <p class="titleinfigure">The Mapping Type Hyperlink</p> |
| <img src="img/mapped_entity_type_link.png" alt="The JPA Details view for an entity showing the mapping type hyperlink." title="The JPA Details view for an entity showing the mapping type hyperlink." /><br /></div> |
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| <p class="notep1">Tip:</p> |
| You can also change add persistence for an entity by right-clicking the class in the JPA Structure View and then clicking <span class="bold">Map As > Entity</span>.</td> |
| </tr> |
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| <br /></div> |
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| </li> |
| <li> |
| <p>Select <span class="bold">Entity</span> from the Mapping Type Selection dialog and then click <span class="bold">OK</span>.</p> |
| <div class="figure"><a id="sthref63" name="sthref63"></a> |
| <p class="titleinfigure">The Mapping Type Selection Dialog</p> |
| <img src="img/mapping_type_selection_entity.png" alt="The Mapping Type selection dialog with Enity selected." title="The Mapping Type selection dialog with Enity selected." /><br /></div> |
| <!-- class="figure" --></li> |
| <li> |
| <p>Complete the remaining <a href="ref_persistence_prop_view.htm#BABFAEBB">JPA Details view (for entities)</a>.</p> |
| </li> |
| </ol> |
| <p> </p> |
| <img src="img/ngrelt.png" alt="Related tasks" title="Related tasks" /><br /> |
| <br /> |
| <a href="task_add_persistence.htm#BABHICAI">Adding persistence to a class</a><br /> |
| <a href="task_additonal_tables.htm#CIHGBIEI">Specifying additional tables</a><br /> |
| <a href="task_inheritance.htm#CIHCCCJD">Specifying entity inheritance</a><br /></div> |
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