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<title>OSCache Features</title>
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<p><b>Fast in-memory caching</b></p>
<ul>
  <li>OSCache allows you to <i>execute dynamic content periodically</i> (eg every
    30 minutes) rather than every request and store the result in memory. Each
    further request is served directly from the memory cache, resulting in dramatic
    speed increases.</li>
  <li><i> The cache is keyed programmatically</i>. This means you can calculate a
    cache key that works for your situation. For example an ecommerce site might use
    product ID as keys, or content site might use an article date and article ID combination.</li>
  <li>The cache is stored in standard scopes that any JSP programmer is familiar with
    (application or session). The session scope allows you to have <i>different
    cached content per user</i>. This is one unlike any other caching system we've
    ever seen.</li>
</ul>

<p><b>Persistent on-disk caching</b></p>
<ul>
  <li>OSCache can also write the cache to disk. This provides <i>caching across
    server restarts</i>, and <i>caching of datasets that do not fit into memory</i>.
    Caching can be configured to use memory or file caching, or a combination of
    both.</li>
  <li>If you want to persist the cache to somewhere other than disk, you can plug in a
    custom PersistenceListener. This allows you to persist the cache to anywhere (for
    example to a database via JDBC or to LDAP via JNDI).</li>
  <li>When using both disk caching and memory caching. It is possible to limit the
    cache size to avoid using too much memory but let disk cache unlimited,
    resulting in browser style complementary disk cache. When cached objects are removed
    from memory, they are still on disk. If the item is needed again and it is not
    expired the cache file will be used. This also gives fault tolerance if the
    server crashes.<br>
  </li>
</ul>

<p><b>Excellent Performance</b></p>
<ul>
  <li>Written with performance in mind.</li>
  <li>Mulitple cache requests can be handled concurrently.</li>
  <li>Only one requesting thread needs to update an expired cache entry even if
    multiple threads are requesting it simultaneously. Other threads can be
    configured to either receive the recently-expired object, or block until the
    cached object is updated. Similarly, when a new entry is being added to the
    cache, other threads requesting that entry will block until it is ready rather
    than run off and race to build the same object. In a high load environment
    this can provide enormous performance benefits.</li>
  <li>Automatically takes advantage of JRE 1.4 or higher if available.</li>
</ul>

<p><b>Clustering support</b></p>
<ul>
  <li>OSCache can easily be configured to cluster across multiple boxes. This
    provides both scalability and failover support without any changes required
    in your caching code.
  </li>
</ul>

<p><b>Flexible Caching System</b></p>
<ul>
  <li>OSCache allows you to cache portions of <i>JSP pages</i>, <i>arbitrary Java objects</i>,
    and even <i>entire servlet responses</i>.</li>
  <li>Cache capacity can be set allowing you to limit the number of cached objects.</li>
  <li>Multiple caching algorithms are supported such as LRU (Least Recently Used),
    FIFO (First In First Out), or unlimited. It is also possible to plug in your own
    custom algorithm.</li>
  <li>You are given a huge amount of control over the way cached objects expire. Objects
    can be cached indefinitely, expired once they reach a certain age, or expired based
    on a cron expression. Programmatic flushing is also possible, and if that is still not
    enough pluggable RefreshPolicies allow custom refresh strategies.
  <li>Cached objects can be grouped together however you like, allowing for powerful
    management of cached data. This is an extremely useful feature that is far more powerful
    than what other caching solutions typically offer (such as the flushing of cache keys
    that match a particular pattern).</li>
  <li>Fully event driven! OSCache fires events for various happenings 'under
    the hood' such as cache entry events (adding, updating, flushing and removing)
    and cache accesses (hit, stale hit and miss). It is easy to add your own event
    handlers.</li>
  <li>Multiple caches can be created, each with their own unique configuration.</li>
</ul>

<p><b>Simple JSP Tag Library</b></p>
<ul>
  <li>The tag library to perform and control the caching is very simple. See
    the <a href="tags.html">Tag Reference</a> for more information.</li>
</ul>

<p><b>Caching Filter</b></p>
<ul>
  <li>A Servlet 2.3 Filter allows for caching of <i>entire pages</i> and
  <i>generated binary files</i> (like dynamically created images or PDF files).
  </li>
</ul>

<p><b>Comprehensive API</b></p>
<ul>
  <li>For the ultimate control, OSCache can be used through its straightforward API. You can
    instantiate, configure and control multiple caches programmatically. It would be possible
    for example to create one small in-memory cache that held currency conversion rates and
    was updated daily at 2am, while another cache could be purely disk based and used for
    holding dynamically created images.</li>
</ul>

<p><b>Exception Handling</b></p>
<ul>
  <li>OSCache provides a way for your site to <i>gracefully tolerate errors</i>.
    This is not error prevention, rather if an error occurs it should not stop
    your site from functioning. For example if your database goes down, normally
    your product descriptions will not be browsable. Using OSCache you can cache
    those descriptions so you can still browse them.</li>
</ul>

<p><b>Cache Flushing</b></p>
<ul>
  <li>Flushing of caches can be controlled via JSP Tags, so these functions can
    easily be built into your administration interface.</li>
  <li>There is programmatic control over what caches are flushed (eg all caches
    or just a particular scope).</li>
  <li>Cached objects can be expired in a number of ways. Objects can be told to expire
    once they reach a certain age, or, through the use of cron expressions, on particular
    dates and/or times (eg it is trivial to make an object expire every weekday
    at 3am). If this is not enough, you can expire objects programmatically as required,
    or plug in your own custom RefreshPolicy class that can dynamically decide when
    an object should be flushed.
    </li>
  <li>Entire groups of objects can be easily flushed from the cache. For example
    suppose you were caching product data as well as entire pages of your website.
    When a product was updated, you could flush not just the product object but
    also all the pages that contain information about that product. No more waiting
    for the cached objects to expire before the updated content shows up on your site!</li>
</ul>

<p><b>Portable caching</b></p>
<ul>
  <li>Pure Java, this means it is platform independent. </li>
  <li>OSCache is compliant with Servlet 2.3 and JSP 1.2 standards, which means
    it should work in the latest generation of servlet containers and application
    servers.</li>
</ul>

<p><b>i18n Aware</b></p>
<ul>
  <li>The caching is i18n aware and supports all encodings.</li>
</ul>

<p><b>Solid Reputation</b></p>
<ul>
  <li>Thousands of downloads, hundreds of users on the
    <a href="http://sourceforge.net/mail/?group_id=9890">mailing list.</a></li>
  <li>Comprehensive <a href="http://www.junit.org">JUnit</a> test suite
    that covers every aspect of OSCache, including a web stress test and
    various concurrent cache access scenarios. To back this up, the kind
    folks at <a href="http://www.cortexebusiness.com.au/">Cortex</a> have
    supplied us with a <a href="http://www.thecortex.net/clover/">Clover</a>
    license to provide detailed code coverage analysis of our unit tests.</li>
  <li>We have solid <a href="http://jira.opensymphony.com">issue tracking</a>
    using <a href="http://www.atlassian.com/software/jira">JIRA</a> to keep
    track of any feature requests, bug reports and development progress.
    JIRA is provided courtesy of <a href="http://www.atlassian.com">Atlassian</a>.</li>
</ul>
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