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| <meta name="doctitle" content="One-to-one mapping" /> |
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| <div class="sect2"><!-- infolevel="all" infotype="General" --> |
| <h1>One-to-one mapping</h1> |
| <p><a id="sthref142" name="sthref142"></a><a id="sthref143" name="sthref143"></a><a id="sthref144" name="sthref144"></a><a id="sthref145" name="sthref145"></a>Use a <span class="bold">One-to-One Mapping</span> to define a relationship with one-to-many multiplicity.</p> |
| <ol> |
| <li> |
| <p>In the <a href="ref_persistence_outline.htm#BABEGGFE">JPA Structure view</a>, select the field to map.</p> |
| </li> |
| <li> |
| <p>Right-click the field and then select <span class="bold">Map As > One-to-One</span>. The <a href="ref_persistence_map_view.htm#BABIFBAF">JPA Details view (for attributes)</a> displays the properties for the selected.</p> |
| </li> |
| <li> |
| <p>Use this table to complete the <a href="ref_mapping_general.htm#CACBHFIJ">General information</a> fields in the JPA Details view.</p> |
| <div class="inftblruleinformal"> |
| <table class="RuleInformal" title="This table lists the fields in the Persistence Properties view for this mapping." summary="This table lists the fields in the Persistence Properties view for this mapping." dir="ltr" border="1" width="100%" frame="border" rules="all" cellpadding="3" cellspacing="0"> |
| <col width="19%" /> |
| <col width="*" /> |
| <col width="41%" /> |
| <thead> |
| <tr align="left" valign="top"> |
| <th align="left" valign="bottom" id="r1c1-t25">Property</th> |
| <th align="left" valign="bottom" id="r1c2-t25">Description</th> |
| <th align="left" valign="bottom" id="r1c3-t25">Default</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr align="left" valign="top"> |
| <td align="left" id="r2c1-t25" headers="r1c1-t25">Mapped Entity Hyperlink</td> |
| <td align="left" headers="r2c1-t25 r1c2-t25">Defines mapping as <span class="bold">One-to-One</span>. This corresponds to the <code>@OneToOne</code> annotation.</td> |
| <td align="left" headers="r2c1-t25 r1c3-t25">One-to-One</td> |
| </tr> |
| <tr align="left" valign="top"> |
| <td align="left" id="r3c1-t25" headers="r1c1-t25">Target Entity</td> |
| <td align="left" headers="r3c1-t25 r1c2-t25">The entity to which this attribute is mapped.</td> |
| <td align="left" headers="r3c1-t25 r1c3-t25">null |
| <p>You do not need to explicitly specify the target entity, since it can be inferred from the type of object being referenced.</p> |
| </td> |
| </tr> |
| <tr align="left" valign="top"> |
| <td align="left" id="r4c1-t25" headers="r1c1-t25">Fetch Type</td> |
| <td align="left" headers="r4c1-t25 r1c2-t25">Defines how data is loaded from the database. See <a href="ref_mapping_general.htm#CACGGGHB">"Fetch Type"</a> for details. |
| <ul> |
| <li> |
| <p>Eager</p> |
| </li> |
| <li> |
| <p>Lazy</p> |
| </li> |
| </ul> |
| </td> |
| <td align="left" headers="r4c1-t25 r1c3-t25">Eager</td> |
| </tr> |
| <tr align="left" valign="top"> |
| <td align="left" id="r5c1-t25" headers="r1c1-t25">Mapped By</td> |
| <td align="left" headers="r5c1-t25 r1c2-t25">The database field that owns the relationship.</td> |
| <td align="left" headers="r5c1-t25 r1c3-t25"><br /></td> |
| </tr> |
| </tbody> |
| </table> |
| <br /></div> |
| <!-- class="inftblruleinformal" --></li> |
| <li> |
| <p>Use this table to complete the <a href="reference012.htm#CACFCEJC">Join Columns Information</a> fields in the <span class="gui-object-title">JPA Details</span> view.</p> |
| <div class="inftblruleinformal"> |
| <table class="RuleInformal" title="This table lists the fields in the Persistence Properties view for this mapping." summary="This table lists the fields in the Persistence Properties view for this mapping." dir="ltr" border="1" width="100%" frame="border" rules="all" cellpadding="3" cellspacing="0"> |
| <col width="19%" /> |
| <col width="*" /> |
| <col width="41%" /> |
| <thead> |
| <tr align="left" valign="top"> |
| <th align="left" valign="bottom" id="r1c1-t26">Property</th> |
| <th align="left" valign="bottom" id="r1c2-t26">Description</th> |
| <th align="left" valign="bottom" id="r1c3-t26">Default</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr align="left" valign="top"> |
| <td align="left" id="r2c1-t26" headers="r1c1-t26">Join Column</td> |
| <td align="left" headers="r2c1-t26 r1c2-t26"><a id="sthref146" name="sthref146"></a><a id="sthref147" name="sthref147"></a>Specify a mapped column for joining an entity association. This field corresponds to the <code>@JoinColum</code> attribute. |
| <p>Select <span class="bold">Override Default</span>, then Add, Edit, or Remove the join columns.</p> |
| </td> |
| <td align="left" headers="r2c1-t26 r1c3-t26">By default, the mapping is assumed to have a single join.</td> |
| </tr> |
| </tbody> |
| </table> |
| <br /></div> |
| <!-- class="inftblruleinformal" --></li> |
| </ol> |
| <p>Eclipse adds the following annotations to the field:</p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| @OneToOne(targetEntity=<span class="italic"><TARGET_ENTITY></span>, cascade=CascadeType.<span class="italic"><CASCADE_TYPE></span>, |
| fetch = FetchType.<span class="italic"><FETCH_TYPE></span>, mappedBy = "<span class="italic"><MAPPED_BY></span>") |
| @JoinColumn(name="<span class="italic"><JOIN_COLUMN_NAME></span>", referencedColumnName= |
| "<span class="italic"><JOIN_COLUMN_REFERENCED_COLUMN></span>", insertable = <span class="italic"><INSERTABLE></span>, |
| updatable = <span class="italic"><UPDATABLE></span>) |
| |
| </pre> |
| <p> </p> |
| <img src="img/ngrelt.png" alt="Related task" title="Related task" /><br /> |
| <br /> |
| <a href="task_mapping.htm#BABDGBIJ">Mapping an entity</a> |
| <p> </p> |
| <img src="img/ngrelr.png" alt="Related reference" title="Related reference" /><br /> |
| <br /> |
| <a href="ref_persistence_outline.htm#BABEGGFE">JPA Structure view</a><br /> |
| <a href="ref_persistence_map_view.htm#BABIFBAF">JPA Details view (for attributes)</a> |
| <p> </p> |
| <img src="img/ngrelc.png" alt="Related concept" title="Related concept" /><br /> |
| <br /> |
| <a href="concept_mapping.htm#BABBDJFI">Understanding OR mappings</a><br /> |
| <a href="concepts001.htm#BABBGFJG">Understanding EJB 3.0 Java Persistence API</a></div> |
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