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</style></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="https://tomcat.apache.org/"><img src="../images/tomcat.gif" align="right" alt="
The Apache Tomcat Servlet/JSP Container
" border="0"></a></td><td><h1><font face="arial,helvetica,sanserif">Apache Tomcat 7</font></h1><font face="arial,helvetica,sanserif">Version 7.0.103, Mar 16 2020</font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="../images/asf-logo.svg" align="right" alt="Apache Logo" border="0" style="width: 266px;height: 83px;"></a></td></tr></table><table border="0" width="100%" cellspacing="4"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--LEFT SIDE NAVIGATION--><td width="20%" valign="top" nowrap class="noPrint"><p><strong>Links</strong></p><ul><li><a href="../index.html">Docs Home</a></li><li><a href="index.html">Config Ref. Home</a></li><li><a href="https://wiki.apache.org/tomcat/FAQ">FAQ</a></li><li><a href="#comments_section">User Comments</a></li></ul><p><strong>Top Level Elements</strong></p><ul><li><a href="server.html">Server</a></li><li><a href="service.html">Service</a></li></ul><p><strong>Executors</strong></p><ul><li><a href="executor.html">Executor</a></li></ul><p><strong>Connectors</strong></p><ul><li><a href="http.html">HTTP</a></li><li><a href="ajp.html">AJP</a></li></ul><p><strong>Containers</strong></p><ul><li><a href="context.html">Context</a></li><li><a href="engine.html">Engine</a></li><li><a href="host.html">Host</a></li><li><a href="cluster.html">Cluster</a></li></ul><p><strong>Nested Components</strong></p><ul><li><a href="globalresources.html">Global Resources</a></li><li><a href="jar-scanner.html">JarScanner</a></li><li><a href="listeners.html">Listeners</a></li><li><a href="loader.html">Loader</a></li><li><a href="manager.html">Manager</a></li><li><a href="realm.html">Realm</a></li><li><a href="resources.html">Resources</a></li><li><a href="sessionidgenerator.html">SessionIdGenerator</a></li><li><a href="valve.html">Valve</a></li></ul><p><strong>Cluster Elements</strong></p><ul><li><a href="cluster.html">Cluster</a></li><li><a href="cluster-manager.html">Manager</a></li><li><a href="cluster-channel.html">Channel</a></li><li><a href="cluster-membership.html">Channel/Membership</a></li><li><a href="cluster-sender.html">Channel/Sender</a></li><li><a href="cluster-receiver.html">Channel/Receiver</a></li><li><a href="cluster-interceptor.html">Channel/Interceptor</a></li><li><a href="cluster-valve.html">Valve</a></li><li><a href="cluster-deployer.html">Deployer</a></li><li><a href="cluster-listener.html">ClusterListener</a></li></ul><p><strong>web.xml</strong></p><ul><li><a href="filter.html">Filter</a></li></ul><p><strong>Other</strong></p><ul><li><a href="systemprops.html">System properties</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left" id="mainBody"><h1>The Loader Component</h1><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Table of Contents"><!--()--></a><a name="Table_of_Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote>
<ul><li><a href="#Introduction">Introduction</a></li><li><a href="#Attributes">Attributes</a><ol><li><a href="#Common_Attributes">Common Attributes</a></li><li><a href="#Standard_Implementation">Standard Implementation</a></li><li><a href="#VirtualWebappLoader_Implementation">VirtualWebappLoader Implementation</a></li></ol></li><li><a href="#Nested_Components">Nested Components</a></li><li><a href="#Special_Features">Special Features</a><ol><li><a href="#Logging">Logging</a></li></ol></li></ul>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>
<p>The <strong>Loader</strong> element represents the <em>web
application class loader</em> that will be used to load Java
classes and resources for your web application. Such
a class loader must follow the requirements of the Servlet
Specification, and load classes from the following locations:</p>
<ul>
<li>From the <code>/WEB-INF/classes</code> directory inside your
web application.</li>
<li>From JAR files in the <code>/WEB-INF/lib</code> directory
inside your web application.</li>
<li>From resources made available by Catalina to all web
applications globally.</li>
</ul>
<p>A Loader element MAY be nested inside a <a href="context.html">Context</a>
component. If it is not included, a default Loader configuration will be
created automatically, which is sufficient for most requirements.</p>
<p>For a more in-depth description of the class loader hierarchy
that is implemented by Catalina, see <a href="../class-loader-howto.html">the ClassLoader HowTo</a>.</p>
<p><em>The description below uses the variable name $CATALINA_BASE to refer the
base directory against which most relative paths are resolved. If you have
not configured Tomcat for multiple instances by setting a CATALINA_BASE
directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
the directory into which you have installed Tomcat.</em></p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Attributes"><strong>Attributes</strong></a></font></td></tr><tr><td><blockquote>
<table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Common Attributes"><!--()--></a><a name="Common_Attributes"><strong>Common Attributes</strong></a></font></td></tr><tr><td><blockquote>
<p>All implementations of <strong>Loader</strong>
support the following attributes:</p>
<table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">className</code></td><td align="left" valign="center">
<p>Java class name of the implementation to use. This class must
implement the <code>org.apache.catalina.Loader</code> interface.
If not specified, the standard value (defined below) will be used.</p>
</td></tr><tr><td align="left" valign="center"><code class="attributeName">delegate</code></td><td align="left" valign="center">
<p>Set to <code>true</code> if you want the class loader to follow
the standard Java2 delegation model, and attempt to load classes from
parent class loaders <strong>before</strong> looking inside the web
application. Set to <code>false</code> (the default) to have the
class loader look inside the web application first, before asking
parent class loaders to find requested classes or resources.</p>
</td></tr><tr><td align="left" valign="center"><code class="attributeName">reloadable</code></td><td align="left" valign="center">
<p>Set to <code>true</code> if you want Catalina to monitor classes in
<code>/WEB-INF/classes/</code> and <code>/WEB-INF/lib</code> for
changes, and automatically reload the web application if a change
is detected. This feature is very useful during application
development, but it requires significant runtime overhead and is
not recommended for use on deployed production applications. You
can use the <a href="../manager-howto.html">Manager</a> web
application, however, to trigger reloads of deployed applications
on demand.</p>
<p><strong>NOTE</strong> - The value for this property will be
inherited from the <code>reloadable</code> attribute you set on
the surrounding <a href="context.html">Context</a> component,
and any value you explicitly set here will be replaced.</p>
</td></tr></table>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Standard Implementation"><!--()--></a><a name="Standard_Implementation"><strong>Standard Implementation</strong></a></font></td></tr><tr><td><blockquote>
<p>The standard implementation of <strong>Loader</strong> is
<strong>org.apache.catalina.loader.WebappLoader</strong>.
It supports the following additional attributes (in addition to the
common attributes listed above):</p>
<table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">loaderClass</code></td><td align="left" valign="center">
<p>Java class name of the <code>java.lang.ClassLoader</code>
implementation class to use. If not specified, the default value is
<code>org.apache.catalina.loader.WebappClassLoader</code>. Custom
<strong>loaderClass</strong> implementations must extend
<code>org.apache.catalina.loader.WebappClassLoaderBase</code>.The
default <strong>loaderClass</strong> is not parallel capable. A parallel
capable <strong>loaderClass</strong> is available when running on a Java
7 or higher JRE and can be used by specifying
<code>org.apache.catalina.loader.ParallelWebappClassLoader</code>.</p>
</td></tr><tr><td align="left" valign="center"><code class="attributeName">searchExternalFirst</code></td><td align="left" valign="center">
<p>Set to <code>true</code> if you want repositories outside
of <code>WEB-INF/classes</code> and <code>WEB-INF/lib</code> to
be searched first. Default value is <code>false</code>.</p>
</td></tr><tr><td align="left" valign="center"><code class="attributeName">jarOpenInterval</code></td><td align="left" valign="center">
<p>The interval in milliseconds to keep all jar files open if no jar
is accessed. The default value is <code>90000</code> milliseconds.
A non-positive interval indicates keeping jars always open.
</p>
</td></tr></table>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="VirtualWebappLoader Implementation"><!--()--></a><a name="VirtualWebappLoader_Implementation"><strong>VirtualWebappLoader Implementation</strong></a></font></td></tr><tr><td><blockquote>
<p>This implementation of <strong>Loader</strong> is
<strong>org.apache.catalina.loader.VirtualWebappLoader</strong>.
It extends <code>WebappLoader</code> and supports the following
additional attributes</p>
<table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">virtualClasspath</code></td><td align="left" valign="center">
<p>Additional repositories to search for resources.
Multiple values can be joined using <code>;</code>
as a separator.</p>
<p>Leading and trailing whitespaces in values are ignored.
If a value does not point to an existing directory or
<code>*.jar</code> file, it is silently skipped.
Diagnostic messages can be seen if you enable debug logging for
the VirtualWebappLoader class.
</p>
<p>Example: <code>virtualClasspath="${catalina.base}/myapp_config"</code></p>
</td></tr><tr><td align="left" valign="center"><code class="attributeName">searchVirtualFirst</code></td><td align="left" valign="center">
<p>Set to <code>true</code> if you want the virtual
class path to be searched before
<code>WEB-INF/classes</code> and <code>WEB-INF/lib</code>.
Default value is <code>false</code>.</p>
<p>If searched before, resources located in the virtual
class path take precendence over resources with the same
name contained in the webapp.</p>
</td></tr></table>
</blockquote></td></tr></table>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Nested Components"><!--()--></a><a name="Nested_Components"><strong>Nested Components</strong></a></font></td></tr><tr><td><blockquote>
<p>No components may be nested inside a <strong>Loader</strong> element.</p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Special Features"><!--()--></a><a name="Special_Features"><strong>Special Features</strong></a></font></td></tr><tr><td><blockquote>
<table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Logging"><strong>Logging</strong></a></font></td></tr><tr><td><blockquote>
<p>A loader is associated with the log category based on its classname.</p>
</blockquote></td></tr></table>
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