Skip to main content
summaryrefslogblamecommitdiffstats
blob: 5cc67ba85082c5ec688d5273e7dfe9d308f70c72 (plain) (tree)
1
2
3
4
5
6
7



                                                                   
                                        
                                                  
                                            





                                                                                        
                                                                







                                                                                               
                                            



                                                                                          
                                      


        
                                                                                                                                                                                                      





                                                                                                                           



                                                                                                                                                                               

                            



                                                                                                              
     




                          
     











































                                                                                                                                                                                                                                                                                                                       
     
                                                               
                                              





                                                                                               


      








                                                                                                                                                                                                   






















                                                                                                                                                                                                
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<!-- Run date = May 15, 2007 9:04:23 -->
<meta name="OAC_IGNORE_SKIP_NAV" content="true" />
<title>Specifying entity inheritance</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta http-equiv="Content-Script-Type" content="text/javascript" />
<meta name="generator" content="Oracle DARB XHTML Converter - Version 4.5.3 Build 02" />
<meta name="date" content="2005-07-10T12:57:20+08:00" />
<meta name="robots" content="all" scheme="http://www.robotstxt.org/" />
<meta name="doctitle" content="Specifying entity inheritance" />
<meta name="relnum" content="Release 1.0.0" />
<meta name="partnum" content="" />
<link rel="copyright" href="dcommon/html/cpyr.htm" title="Copyright" type="text/html" />
<link rel="stylesheet" href="dcommon/css/blafdoc.css" title="Oracle BLAFDoc" type="text/css" />
<link rel="start" href="../../index.htm" title="Home" type="text/html" />
<link rel="contents" href="toc.htm" title="Contents" type="text/html" />
</head>
<body>
<p><a id="CIHCCCJD" name="CIHCCCJD"></a></p>
<div class="sect1"><!-- infolevel="all" infotype="General" -->
<table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%">
<tr valign="bottom">
<td align="left" width="86%">
<h1>Specifying entity inheritance</h1>
</td>
</tr>
</table>
<p><a id="sthref100" name="sthref100"></a><a id="sthref101" name="sthref101"></a>An entity may inherit properties from other entities. You can specify a specific strategy to use for inheritance.</p>
<p>Use this procedure to specify inheritance (<code>@Inheritance)</code> for an existing entity (<code>@Entity</code>):</p>
<ol type="1" start="1">
<li>
<p>Select the entity in the <span class="gui-object-title">Package Explorer</span>.</p>
</li>
<li>
<p>In the <span class="gui-object-title">JPA Details</span> view, select the <span class="gui-object-action">Inheritance</span> information.</p>
<div class="figure"><a id="sthref102" name="sthref102"></a>
<p class="titleinfigure">Specifying Inheritance</p>
<img src="img/inheritance_tab.png" alt="Selecting the Inheritance area on the JPA Details view." title="Selecting the Inheritance area on the JPA Details view." /><br /></div>
<!-- class="figure" --></li>
<li>
<p>In the <span class="bold">Strategy</span> list, select one of the following the inheritance strategies:</p>
<ul>
<li type="disc">
<p>A single table (default)</p>
</li>
<li type="disc">
<p>Joined table</p>
</li>
<li type="disc">
<p>One table per class</p>
</li>
</ul>
</li>
<li>
<p>Use the following table to complete the remaining fields on the tab. See <a href="reference005.htm#CACFHGHE">"Inheritance information"</a> for additional details.</p>
<div class="inftblruleinformal">
<table class="RuleInformal" title="This table describes the options on the Persistence Properties view, Inheritance tab." summary="This table describes the options on the Persistence Properties view, Inheritance tab." dir="ltr" border="1" width="100%" frame="border" rules="all" cellpadding="3" cellspacing="0">
<thead>
<tr align="left" valign="top">
<th align="left" valign="bottom" id="r1c1-t3">Property</th>
<th align="left" valign="bottom" id="r1c2-t3">Description</th>
<th align="left" valign="bottom" id="r1c3-t3">Default</th>
</tr>
</thead>
<tbody>
<tr align="left" valign="top">
<td align="left" id="r2c1-t3" headers="r1c1-t3"><a id="sthref103" name="sthref103"></a><a id="sthref104" name="sthref104"></a>Discriminator Column</td>
<td align="left" headers="r2c1-t3 r1c2-t3">Name of the discriminator column when using a <span class="bold">Single</span> or <span class="bold">Joined</span> inheritance strategy.
<p>This field corresponds to the <code>@DiscriminatorColumn</code> annotation.</p>
</td>
<td align="left" headers="r2c1-t3 r1c3-t3"><br /></td>
</tr>
<tr align="left" valign="top">
<td align="left" id="r3c1-t3" headers="r1c1-t3">Discriminator Type</td>
<td align="left" headers="r3c1-t3 r1c2-t3">Set the discriminator type to <code>Char</code> or <code>Integer</code> (instead of its default: <code>String</code>). The <span class="bold">Discriminator Value</span> must conform to this type.</td>
<td align="left" headers="r3c1-t3 r1c3-t3">String</td>
</tr>
<tr align="left" valign="top">
<td align="left" id="r4c1-t3" headers="r1c1-t3"><a id="sthref105" name="sthref105"></a><a id="sthref106" name="sthref106"></a>Discriminator Value</td>
<td align="left" headers="r4c1-t3 r1c2-t3">Specify the discriminator value used to differentiate an entity in this inheritance hierarchy. The value must conform to the specified <span class="bold">Discriminator Type</span>.
<p>This field corresponds to the <code>@DiscriminatorValue</code> annotation.</p>
</td>
<td align="left" headers="r4c1-t3 r1c3-t3"><br /></td>
</tr>
<tr align="left" valign="top">
<td align="left" id="r5c1-t3" headers="r1c1-t3">Override Default</td>
<td align="left" headers="r5c1-t3 r1c2-t3">Use this field to specify custom primary key join columns.
<p>This field corresponds to the <code>@PrimaryKeyJoinClumn</code> annotation.</p>
</td>
<td align="left" headers="r5c1-t3 r1c3-t3"><br /></td>
</tr>
</tbody>
</table>
<br /></div>
<!-- class="inftblruleinformal" --></li>
</ol>
<p>Eclipse adds the following annotations the entity field:</p>
<pre xml:space="preserve" class="oac_no_warn">
@Inheritance(strategy=InheritanceType.<span class="italic">&lt;INHERITANCE_STRATEGY&gt;</span>)
@DiscriminatorColumn(name="<span class="italic">&lt;DISCRIMINATOR_COLUMN&gt;</span>",
    discriminatorType=<span class="italic">&lt;DISCRIMINATOR_TYPE&gt;</span>)
@DiscriminatorValue(value-"<span class="italic">&lt;DISCRIMINATOR_VALUE&gt;</span>")
@PrimaryKeyJoinColumn(name="<span class="italic">&lt;JOIN_COLUMN_NAME&gt;</span>", 
    referencedColumnName = "<span class="italic">&lt;REFERENCED_COLUMN_NAME&gt;</span>")


</pre>
<p><a id="sthref107" name="sthref107"></a><a id="sthref108" name="sthref108"></a><a id="sthref109" name="sthref109"></a>The following figures illustrates the different inheritance strategies.</p>
<div class="figure"><a id="sthref110" name="sthref110"></a>
<p class="titleinfigure">Single Table Inheritance</p>
<img src="img/inheritance_single.png" alt="This figure illustrates entity inheritance in a single table." title="This figure illustrates entity inheritance in a single table." /><br /></div>
<!-- class="figure" -->
<div class="figure"><a id="sthref111" name="sthref111"></a>
<p class="titleinfigure"><a id="sthref112" name="sthref112"></a><a id="sthref113" name="sthref113"></a>Joined Table Inheritance</p>
<img src="img/inheritance_join.png" alt="This figure shows a sample joined inheritance table strategy." title="This figure shows a sample joined inheritance table strategy." /><br /></div>
<!-- class="figure" -->
<p>&nbsp;</p>
<img src="img/ngrelr.png" alt="Related reference" title="Related reference" /><br />
<br />
<p>&nbsp;</p>
<img src="img/ngrelt.png" alt="Related task" title="Related task" /><br />
<br />
<a href="task_add_persistence.htm#BABHICAI">Adding persistence to a class</a>
<p>&nbsp;</p>
<img src="img/ngrelc.png" alt="Related concept" title="Related concept" /><br />
<br />
<a href="concept_persistence.htm#BABCAHIC">Understanding Java persistence</a><br /></div>
<!-- class="sect1" -->
<!-- Start Footer -->
<div class="footer">
<table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%">
<tr>
<td align="left" width="86%"><a href="dcommon/html/cpyr.htm"><span class="copyrightlogo">Copyright&nbsp;&copy;&nbsp;2006, 2007,&nbsp;Oracle.&nbsp;All&nbsp;rights&nbsp;reserved.</span></a></td>
</tr>
</table>
</div>
<!-- class="footer" -->
</body>
</html>

Back to the top