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     <a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/core-developers/ognl-cache-configuration.md" title="Edit this page on GitHub">Edit on GitHub</a>
     <h1 id="ognl-cache-configuration">OGNL Cache Configuration</h1>

 <p>The Struts framework provides two different OGNL caches, an expression cache and a BeanInfo cache.
 Developers may set properties in <a href="struts-xml">struts.xml</a> and/or <a href="default-properties">default.properties</a> to
 configure certain behaviours for the OGNL caches.  The properties that can be set vary between Struts
 versions, referring to the configuration files in a given version should provide guidance in that respect.</p>

 <p>The OGNL expression cache is enabled by default.  Developers can toggle that state via default.properties:</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.ognl.enableExpressionCache=true
 </code></pre></div></div>
 <p>or</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.ognl.enableExpressionCache=false
 </code></pre></div></div>
 <p>The same toggle is also available via struts.xml:</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>&lt;constant name="struts.ognl.enableExpressionCache" value="true"/&gt;
 </code></pre></div></div>
 <p>or</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>&lt;constant name="struts.ognl.enableExpressionCache" value="false"/&gt;
 </code></pre></div></div>

 <p>Disabling the OGNL expression cache can have a negative impact on performance, but
 disabling the cache can limit memory overhead for the application (a trade-off).</p>

 <p>As of Struts 6.0.0, additional configuration properties have been made available to control the
 OGNL cache configuration.  These include a configureable cache size limit, and activating
 an LRU (Least Recently Used) cache mode.  The expression cache and BeanInfo cache can have
 their properties set independently.  Both caches are standard caches with a high maximum
 capacity by default.  The developer may override the default behaviour using the
 appropriate configuration properties.</p>

 <p>Below are some examples of setting the cache configuration via default.properties:</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>### Set expression and BeanInfo caches to size 1250 with standard cache mode
 struts.ognl.enableExpressionCache=true
 struts.ognl.expressionCacheMaxSize=1250
 struts.ognl.expressionCacheLRUMode=false
 struts.ognl.beanInfoCacheMaxSize=1250
 struts.ognl.beanInfoCacheLRUMode=false
 </code></pre></div></div>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>### Set expression and BeanInfo caches to size 1000 with LRU cache mode
 struts.ognl.enableExpressionCache=true
 struts.ognl.expressionCacheMaxSize=1000
 struts.ognl.expressionCacheLRUMode=true
 struts.ognl.beanInfoCacheMaxSize=1000
 struts.ognl.beanInfoCacheLRUMode=true
 </code></pre></div></div>

 <p>Below are some examples of setting the cache configuration via struts.xml:</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>&lt;!-- Set expression and BeanInfo caches to size 1250 with standard cache mode --&gt;
 &lt;constant name="struts.ognl.enableExpressionCache" value="true"/&gt;
 &lt;constant name="struts.ognl.expressionCacheMaxSize" value="1250"/&gt;
 &lt;constant name="struts.ognl.expressionCacheLRUMode" value="false"/&gt;
 &lt;constant name="struts.ognl.beanInfoCacheMaxSize" value="1250"/&gt;
 &lt;constant name="struts.ognl.beanInfoCacheLRUMode" value="false"/&gt;
 </code></pre></div></div>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>&lt;!-- Set expression and BeanInfo caches to size 1000 with LRU cache mode --&gt;
 &lt;constant name="struts.ognl.enableExpressionCache" value="true"/&gt;
 &lt;constant name="struts.ognl.expressionCacheMaxSize" value="1000"/&gt;
 &lt;constant name="struts.ognl.expressionCacheLRUMode" value="true"/&gt;
 &lt;constant name="struts.ognl.beanInfoCacheMaxSize" value="1000"/&gt;
 &lt;constant name="struts.ognl.beanInfoCacheLRUMode" value="true"/&gt;
 </code></pre></div></div>

 <p>As of Struts 6.0.0, developers may choose to implement their own OGNL cache factories,
 instead of using the default implementations, should they desire to.  The default
 implementations can be referenced to give an idea of how to implement a custom implementation.
 For example, if a developer implements a CustomExpressionCacheFactory and CustomBeanInfoCacheFactory
 that both implement the OgnlCacheFactory interface, they could be installed via
 a configuration in struts.xml:</p>
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>&lt;constant name="struts.ognl.expressionCacheFactory" value="some.package.CustomExpressionCacheFactory"/&gt;
 &lt;constant name="struts.ognl.beanInfoCacheFactory" value="some.package.CustomBeanInfoCacheFactory"/&gt;
 </code></pre></div></div>
 <p>If the developer wants the standard configuration properties for the caches to function, they will need
 to implement equivalent methods to the ones the default implementation uses to populate those properties.</p>

 <p>Beyond the configuration properties, in certain circumstances, developers may choose to utilize certain methods to
 interact with the OGNL caches.  Refer to the API documentation for <a href="https://struts.apache.org/maven/struts2-core/apidocs/com/opensymphony/xwork2/ognl/OgnlUtil.html">OgnlUtil</a>.</p>

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	<a class="edit-on-gh" href="https://github.com/apache/struts-site/edit/master/source/core-developers/ognl-cache-configuration.md" title="Edit this page on GitHub">Edit on GitHub</a>
	<h1 id="ognl-cache-configuration">OGNL Cache Configuration</h1>

	<p>The Struts framework provides two different OGNL caches, an expression cache and a BeanInfo cache.
	Developers may set properties in <a href="struts-xml">struts.xml</a> and/or <a href="default-properties">default.properties</a> to
	configure certain behaviours for the OGNL caches. The properties that can be set vary between Struts
	versions, referring to the configuration files in a given version should provide guidance in that respect.</p>

	<p>The OGNL expression cache is enabled by default. Developers can toggle that state via default.properties:</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.ognl.enableExpressionCache=true
	</code></pre></div></div>
	<p>or</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.ognl.enableExpressionCache=false
	</code></pre></div></div>
	<p>The same toggle is also available via struts.xml:</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code><constant name="struts.ognl.enableExpressionCache" value="true"/>
	</code></pre></div></div>
	<p>or</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code><constant name="struts.ognl.enableExpressionCache" value="false"/>
	</code></pre></div></div>

	<p>Disabling the OGNL expression cache can have a negative impact on performance, but
	disabling the cache can limit memory overhead for the application (a trade-off).</p>

	<p>As of Struts 6.0.0, additional configuration properties have been made available to control the
	OGNL cache configuration. These include a configureable cache size limit, and activating
	an LRU (Least Recently Used) cache mode. The expression cache and BeanInfo cache can have
	their properties set independently. Both caches are standard caches with a high maximum
	capacity by default. The developer may override the default behaviour using the
	appropriate configuration properties.</p>

	<p>Below are some examples of setting the cache configuration via default.properties:</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>### Set expression and BeanInfo caches to size 1250 with standard cache mode
	struts.ognl.enableExpressionCache=true
	struts.ognl.expressionCacheMaxSize=1250
	struts.ognl.expressionCacheLRUMode=false
	struts.ognl.beanInfoCacheMaxSize=1250
	struts.ognl.beanInfoCacheLRUMode=false
	</code></pre></div></div>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>### Set expression and BeanInfo caches to size 1000 with LRU cache mode
	struts.ognl.enableExpressionCache=true
	struts.ognl.expressionCacheMaxSize=1000
	struts.ognl.expressionCacheLRUMode=true
	struts.ognl.beanInfoCacheMaxSize=1000
	struts.ognl.beanInfoCacheLRUMode=true
	</code></pre></div></div>

	<p>Below are some examples of setting the cache configuration via struts.xml:</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code><!-- Set expression and BeanInfo caches to size 1250 with standard cache mode -->
	<constant name="struts.ognl.enableExpressionCache" value="true"/>
	<constant name="struts.ognl.expressionCacheMaxSize" value="1250"/>
	<constant name="struts.ognl.expressionCacheLRUMode" value="false"/>
	<constant name="struts.ognl.beanInfoCacheMaxSize" value="1250"/>
	<constant name="struts.ognl.beanInfoCacheLRUMode" value="false"/>
	</code></pre></div></div>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code><!-- Set expression and BeanInfo caches to size 1000 with LRU cache mode -->
	<constant name="struts.ognl.enableExpressionCache" value="true"/>
	<constant name="struts.ognl.expressionCacheMaxSize" value="1000"/>
	<constant name="struts.ognl.expressionCacheLRUMode" value="true"/>
	<constant name="struts.ognl.beanInfoCacheMaxSize" value="1000"/>
	<constant name="struts.ognl.beanInfoCacheLRUMode" value="true"/>
	</code></pre></div></div>

	<p>As of Struts 6.0.0, developers may choose to implement their own OGNL cache factories,
	instead of using the default implementations, should they desire to. The default
	implementations can be referenced to give an idea of how to implement a custom implementation.
	For example, if a developer implements a CustomExpressionCacheFactory and CustomBeanInfoCacheFactory
	that both implement the OgnlCacheFactory interface, they could be installed via
	a configuration in struts.xml:</p>
	<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code><constant name="struts.ognl.expressionCacheFactory" value="some.package.CustomExpressionCacheFactory"/>
	<constant name="struts.ognl.beanInfoCacheFactory" value="some.package.CustomBeanInfoCacheFactory"/>
	</code></pre></div></div>
	<p>If the developer wants the standard configuration properties for the caches to function, they will need
	to implement equivalent methods to the ones the default implementation uses to populate those properties.</p>

	<p>Beyond the configuration properties, in certain circumstances, developers may choose to utilize certain methods to
	interact with the OGNL caches. Refer to the API documentation for <a href="https://struts.apache.org/maven/struts2-core/apidocs/com/opensymphony/xwork2/ognl/OgnlUtil.html">OgnlUtil</a>.</p>

	</section>
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