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<span class="cd-toc-link active">Cayenne Guide 5.0</span><div id="toc" class="toc toc-side">
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Table of Contents
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<li><a href="/docs/5.0/cayenne-guide/object-relational-mapping-with-cayenne" class="nav-link" id="object-relational-mapping-with-cayenne">1. Object Relational Mapping with Cayenne</a>
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<li><a href="/docs/5.0/cayenne-guide/setup" class="nav-link" id="setup">1.1. Setup</a></li>
<li><a href="/docs/5.0/cayenne-guide/cayenne-mapping-structure" class="nav-link" id="cayenne-mapping-structure">1.2. Cayenne Mapping Structure</a></li>
<li><a href="/docs/5.0/cayenne-guide/cayenne-modeler" class="nav-link" id="cayenne-modeler">1.3. CayenneModeler Application</a></li>
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<li><a href="/docs/5.0/cayenne-guide/cayenne-framework" class="nav-link" id="cayenne-framework">2. Cayenne Framework</a>
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<li><a href="/docs/5.0/cayenne-guide/including-cayenne-in-project" class="nav-link" id="including-cayenne-in-project">2.1. Including Cayenne in a Project</a></li>
<li><a href="/docs/5.0/cayenne-guide/starting-cayenne" class="nav-link" id="starting-cayenne">2.2. Starting Cayenne</a></li>
<li><a href="/docs/5.0/cayenne-guide/persistent-objects-objectcontext" class="nav-link" id="persistent-objects-objectcontext">2.3. Persistent Objects and ObjectContext</a></li>
<li><a href="/docs/5.0/cayenne-guide/expressions" class="nav-link" id="expressions">2.4. Expressions</a></li>
<li><a href="/docs/5.0/cayenne-guide/orderings" class="nav-link" id="orderings">2.5. Orderings</a></li>
<li><a href="/docs/5.0/cayenne-guide/queries" class="nav-link" id="queries">2.6. Queries</a></li>
<li><a href="/docs/5.0/cayenne-guide/lifecycle-events" class="nav-link" id="lifecycle-events">2.7. Lifecycle Events</a></li>
<li><a href="/docs/5.0/cayenne-guide/performance-tuning" class="nav-link" id="performance-tuning">2.8. Performance Tuning</a></li>
<li><a href="/docs/5.0/cayenne-guide/customizing-cayenne-runtime" class="nav-link" id="customizing-cayenne-runtime">2.9. Customizing Cayenne Runtime</a></li>
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<li><a href="/docs/5.0/cayenne-guide/db-first-flow" class="nav-link" id="db-first-flow">3. DB-First Flow</a>
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<li><a href="/docs/5.0/cayenne-guide/re-introduction" class="nav-link" id="re-introduction">3.1. Introduction</a></li>
<li><a href="/docs/5.0/cayenne-guide/re-filtering" class="nav-link" id="re-filtering">3.2. Filtering</a></li>
<li><a href="/docs/5.0/cayenne-guide/re-relationships-loading-control" class="nav-link" id="re-relationships-loading-control">3.3. Other Settings</a></li>
<li><a href="/docs/5.0/cayenne-guide/re-modeler" class="nav-link" id="re-modeler">3.4. Reverse Engineering in Cayenne Modeler</a></li>
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<li><a href="/docs/5.0/cayenne-guide/additional-modules" class="nav-link" id="additional-modules">4. Additional Modules</a>
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<li><a href="/docs/5.0/cayenne-guide/ext-cache-invalidation" class="nav-link" id="ext-cache-invalidation">4.1. Cache Invalidation Extension</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-commit-log" class="nav-link" id="ext-commit-log">4.2. Commit log extension</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-crypto" class="nav-link" id="ext-crypto">4.3. Crypto extension</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-jcache" class="nav-link" id="ext-jcache">4.4. JCache integration</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-project-compatibility" class="nav-link" id="ext-project-compatibility">4.5. Project compatibility extension</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-velocity" class="nav-link" id="ext-velocity">4.6. Apache Velocity Extension</a></li>
<li><a href="/docs/5.0/cayenne-guide/ext-osgi" class="nav-link" id="ext-osgi">4.7. Cayenne OSGI extension</a></li>
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<li><a href="/docs/5.0/cayenne-guide/build_tools" class="nav-link" id="build_tools">5. Build Tools</a>
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<li><a href="/docs/5.0/cayenne-guide/maven_plugin" class="nav-link" id="maven_plugin">5.1. Maven Plugin</a></li>
<li><a href="/docs/5.0/cayenne-guide/gradle_plugin" class="nav-link" id="gradle_plugin">5.2. Gradle Plugin</a></li>
<li><a href="/docs/5.0/cayenne-guide/ant_tasks" class="nav-link" id="ant_tasks">5.3. Ant Tasks</a></li>
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<li><a href="/docs/5.0/cayenne-guide/appendix-a-configuration-properties" class="nav-link" id="appendix-a-configuration-properties">6. Appendix A. Configuration Properties</a></li>
<li><a href="/docs/5.0/cayenne-guide/appendix-b-service-collections" class="nav-link" id="appendix-b-service-collections">7. Appendix B. Service Collections</a></li>
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<section>
<div class="sect2">
<h3 id="ext-velocity"><a class="anchor" href="#ext-velocity"></a>4.6. Apache Velocity Extension</h3>
<div class="paragraph">
<p>Enables usage of full featured Apache Velocity templates in <code>SQLSelect</code> / <code>SQLExec</code> queries.</p>
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<h4 id="maven-7"><a class="anchor" href="#maven-7"></a>4.6.1. Maven</h4>
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<pre class="highlight"><code class="language-XML XML" data-lang="XML">&lt;dependency&gt;
&lt;groupId&gt;org.apache.cayenne&lt;/groupId&gt;
&lt;artifactId&gt;cayenne-velocity&lt;/artifactId&gt;
&lt;version&gt;5.0-SNAPSHOT&lt;/version&gt;
&lt;/dependency&gt;</code></pre>
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<h4 id="gradle-7"><a class="anchor" href="#gradle-7"></a>4.6.2. Gradle</h4>
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<pre class="highlight"><code class="language-Groovy Groovy" data-lang="Groovy">compile 'org.apache.cayenne:cayenne-velocity:5.0-SNAPSHOT'</code></pre>
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<h4 id="usage-6"><a class="anchor" href="#usage-6"></a>4.6.3. Usage</h4>
<div class="paragraph">
<p>This module doesn’t require any additional setup. In addition of directives mentioned in <a href="/docs/5.0/cayenne-guide/queries#directives">this chapter</a>, this module also adds <code>#chain</code> and <code>#chunk</code> directives.</p>
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<div class="paragraph">
<p><code>#chain</code> and <code>#chunk</code> directives are used for conditional inclusion of SQL code. They are used together with <code>#chain</code> wrapping multiple <code>#chunks</code>. A chunk evaluates its parameter expression and if it is NULL suppresses rendering of the enclosed SQL block. A chain renders its prefix and its chunks joined by the operator. If all the chunks are suppressed, the chain itself is suppressed. This allows to work with otherwise hard to script SQL semantics. E.g. a WHERE clause can contain multiple conditions joined with AND or OR. Application code would like to exclude a condition if its right-hand parameter is not present (similar to Expression pruning discussed above). If all conditions are excluded, the entire WHERE clause should be excluded. chain/chunk allows to do that.</p>
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<p>Semantics:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>#chain(operator) ... #end
#chain(operator prefix) ... #end
#chunk() ... #end
#chunk(param) ... #end</code></pre>
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<div class="paragraph">
<p>Full example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>#chain('OR' 'WHERE')
#chunk($name) NAME LIKE #bind($name) #end
#chunk($id) ARTIST_ID &gt; #bind($id) #end
#end"</code></pre>
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