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<p><a id="BABGBIEE" name="BABGBIEE"></a></p>
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<h1>Entity</h1>
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<p><a id="sthref76" name="sthref76"></a><a id="sthref77" name="sthref77"></a><a id="sthref78" name="sthref78"></a><a id="sthref79" name="sthref79"></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 type="disc">
<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 type="disc">
<p>A no-arg constructor (public or protected); the entity class may have other constructors as well.</p>
</li>
</ul>
<p><a id="sthref80" name="sthref80"></a><a id="sthref81" name="sthref81"></a><a id="sthref82" name="sthref82"></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 type="1" 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>
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<li>
<p>In the <span class="gui-object-title">JPA Details</span> view, use the <span class="gui-object-action">Map As</span> field to select <span class="gui-object-action">Entity</span>.</p>
<div class="figure"><a id="sthref83" name="sthref83"></a>
<p class="titleinfigure">Selecting Entity Persistence</p>
<img src="img/persistence_view_entity.png" alt="Selecting entity persistence on the JPA Details view." title="Selecting entity persistence on the JPA Details view." /><br /></div>
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<li>
<p>Complete the remaining <a href="ref_persistence_prop_view.htm#BABFAEBB">JPA Details view (for entities)</a>.</p>
</li>
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<p>&nbsp;</p>
<img src="img/ngrelt.png" alt="Related tasks" title="Related tasks" /><br />
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<a href="task_add_persistence.htm#BABHICAI">Adding persistence to a class</a></div>
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