docs/1.2/tutorial-delete.html

Title: Tutorial Delete

	

<P>Before we discuss the API for object deletion, lets go back to CayenneModeler and set up some <A href="delete-rules.html" title="Delete Rules">delete rules</A>. Doing this is optional but will simplify correct handling of the objects related to deleted  objects.</P>

<UL>
	<LI>In the Modeler go to &quot;Artist&quot; ObjEntity, &quot;Relationships&quot; tab and select &quot;Cascade&quot; for the &quot;paintings&quot; relationship delete rule:</LI>
</UL>


<P><SPAN class="image-wrap" style=""><IMG src="tutorial-delete.data/delete-rule.jpg" style="border: 0px solid black"></SPAN></P>

<UL>
	<LI>Repeat this step for Gallery (set &quot;paintings&quot; relationship to be &quot;Cascade&quot;)</LI>
	<LI>Repeat this step for Painting (set both relationships rules to &quot;Nullify&quot;).</LI>
	<LI>Save the mapping, and refresh the porject in Eclispe.</LI>
</UL>


<UL>
	<LI>To delete an object we first need to get a hold of this object. Let's use utility class DataObjectUtils to find an artist:</LI>
</UL>


<DIV class="code panel" style="border-width: 1px;"><DIV class="codeHeader panelHeader" style="border-bottom-width: 1px;"><B>Main.java</B></DIV><DIV class="codeContent panelContent">
<PRE class="code-java">Expression qualifier = ExpressionFactory.matchExp(Artist.NAME_PROPERTY, <SPAN class="code-quote">&quot;Pablo Picasso&quot;</SPAN>);
SelectQuery select = <SPAN class="code-keyword">new</SPAN> SelectQuery(Artist.class, qualifier);

Artist picasso = (Artist) DataObjectUtils.objectForQuery(context, select);</PRE>
</DIV></DIV>

<P>Now let's delete the artist:</P>
<DIV class="code panel" style="border-width: 1px;"><DIV class="codeHeader panelHeader" style="border-bottom-width: 1px;"><B>Main.java</B></DIV><DIV class="codeContent panelContent">
<PRE class="code-java"><SPAN class="code-keyword">if</SPAN> (picasso != <SPAN class="code-keyword">null</SPAN>) {
    context.deleteObject(picasso);
    context.commitChanges();
}</PRE>
</DIV></DIV>

<P>Since we set up &quot;Cascade&quot; delete rule for the Artist.paintings relationships, Cayenne will automatically delete all paintings of this artist. So when your run the app you'll see this output:</P>

<DIV class="preformatted panel" style="border-width: 1px;"><DIV class="preformattedContent panelContent">
<PRE>INFO  QueryLogger: --- will run 2 queries.
INFO  QueryLogger: --- transaction started.
INFO  QueryLogger: DELETE FROM PAINTING WHERE ID = ?
INFO  QueryLogger: [bind: 361]
INFO  QueryLogger: === updated 1 row.
INFO  QueryLogger: [bind: 360]
INFO  QueryLogger: === updated 1 row.
INFO  QueryLogger: DELETE FROM ARTIST WHERE ID = ?
INFO  QueryLogger: [bind: 360]
INFO  QueryLogger: === updated 1 row.
INFO  QueryLogger: +++ transaction committed.</PRE>
</DIV></DIV>

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