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<html>
<head>
<title>OSCache -
Usage
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<p>Beside the <a href="JSP Tags.html" title="JSP Tags">JSP tag library</a> and the <a href="CacheFilter.html" title="CacheFilter">CacheFilter</a> you can use OSCache through its straightforward API. You can use the <a href="http://www.opensymphony.com/oscache/api/com/opensymphony/oscache/general/GeneralCacheAdministrator.html" title="Visit page outside Confluence">GeneralCacheAdministrator</a> to create, flush and administrate the cache. The GeneralCacheAdministrator has a cache instance and delegates different Cache's methods. Furthermore the GeneralCacheAdministrator is in charge of load the <a href="Configuration.html" title="Configuration">cache.properties</a> and create a cache instance with the properties definded. You have to store an instance of the GeneralCacheAdministrator in a static value or use a singleton pattern to access the same GeneralCacheAdministrator.</p>
<h4><a name="APIUsage-Typicalusewithfailover"></a>Typical use with fail over</h4>
<div class="code"><div class="codeContent">
<pre class="code-java"><span class="code-object">String</span> myKey = <span class="code-quote">"myKey"</span>;
<span class="code-object">String</span> myValue;
<span class="code-object">int</span> myRefreshPeriod = 1000;
<span class="code-keyword">try</span> {
<span class="code-comment">// Get from the cache
</span> myValue = (<span class="code-object">String</span>) admin.getFromCache(myKey, myRefreshPeriod);
} <span class="code-keyword">catch</span> (NeedsRefreshException nre) {
<span class="code-keyword">try</span> {
<span class="code-comment">// Get the value (probably from the database)
</span> myValue = <span class="code-quote">"This is the content retrieved."</span>;
<span class="code-comment">// Store in the cache
</span> admin.putInCache(myKey, myValue);
} <span class="code-keyword">catch</span> (Exception ex) {
<span class="code-comment">// We have the current content <span class="code-keyword">if</span> we want fail-over.
</span> myValue = (<span class="code-object">String</span>) nre.getCacheContent();
<span class="code-comment">// It is essential that cancelUpdate is called <span class="code-keyword">if</span> the
</span> <span class="code-comment">// cached content is not rebuilt
</span> admin.cancelUpdate(myKey);
}
}</pre>
</div></div>
<h4><a name="APIUsage-Typicalusewithoutfailover"></a>Typical use without fail over</h4>
<div class="code"><div class="codeContent">
<pre class="code-java"><span class="code-object">String</span> myKey = <span class="code-quote">"myKey"</span>;
<span class="code-object">String</span> myValue;
<span class="code-object">int</span> myRefreshPeriod = 1000;
<span class="code-keyword">try</span> {
<span class="code-comment">// Get from the cache
</span> myValue = (<span class="code-object">String</span>) admin.getFromCache(myKey, myRefreshPeriod);
} <span class="code-keyword">catch</span> (NeedsRefreshException nre) {
<span class="code-keyword">try</span> {
<span class="code-comment">// Get the value (probably from the database)
</span> myValue = <span class="code-quote">"This is the content retrieved."</span>;
<span class="code-comment">// Store in the cache
</span> admin.putInCache(myKey, myValue);
updated = <span class="code-keyword">true</span>;
} <span class="code-keyword">finally</span> {
<span class="code-keyword">if</span> (!updated) {
<span class="code-comment">// It is essential that cancelUpdate is called <span class="code-keyword">if</span> the
</span> <span class="code-comment">// cached content could not be rebuilt
</span> admin.cancelUpdate(myKey);
}
}
}</pre>
</div></div>
<h4><a name="APIUsage-Note"></a>Note</h4>
<table cellpadding='5' width='85%' cellspacing='8px' class='noteMacro' border="0" align='center'><colgroup><col width='24'><col></colgroup><tr><td valign='top'><img src="./icons/emoticons/warning.gif" width="16" height="16" align="absmiddle" alt="" border="0"></td><td><b class="strong">Be Careful</b><br />
<p>If a NeedsRefreshException is raised you have to invoke admin.putInCache or even admin.cancelUpdate to avoid deadlock situation.</p></td></tr></table>
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