<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Apache Tomcat 7 Configuration Reference (7.0.77) - The Loader Component</title><meta name="author" content="Craig R. McClanahan"><style type="text/css" media="print"> | |
.noPrint {display: none;} | |
td#mainBody {width: 100%;} | |
</style><style type="text/css"> | |
code {background-color:rgb(224,255,255);padding:0 0.1em;} | |
code.attributeName, code.propertyName {background-color:transparent;} | |
table { | |
border-collapse: collapse; | |
text-align: left; | |
} | |
table *:not(table) { | |
/* Prevent border-collapsing for table child elements like <div> */ | |
border-collapse: separate; | |
} | |
th { | |
text-align: left; | |
} | |
div.codeBox pre code, code.attributeName, code.propertyName, code.noHighlight, .noHighlight code { | |
background-color: transparent; | |
} | |
div.codeBox { | |
overflow: auto; | |
margin: 1em 0; | |
} | |
div.codeBox pre { | |
margin: 0; | |
padding: 4px; | |
border: 1px solid #999; | |
border-radius: 5px; | |
background-color: #eff8ff; | |
display: table; /* To prevent <pre>s from taking the complete available width. */ | |
/* | |
When it is officially supported, use the following CSS instead of display: table | |
to prevent big <pre>s from exceeding the browser window: | |
max-width: available; | |
width: min-content; | |
*/ | |
} | |
div.codeBox pre.wrap { | |
white-space: pre-wrap; | |
} | |
table.defaultTable tr, table.detail-table tr { | |
border: 1px solid #CCC; | |
} | |
table.defaultTable tr:nth-child(even), table.detail-table tr:nth-child(even) { | |
background-color: #FAFBFF; | |
} | |
table.defaultTable tr:nth-child(odd), table.detail-table tr:nth-child(odd) { | |
background-color: #EEEFFF; | |
} | |
table.defaultTable th, table.detail-table th { | |
background-color: #88b; | |
color: #fff; | |
} | |
table.defaultTable th, table.defaultTable td, table.detail-table th, table.detail-table td { | |
padding: 5px 8px; | |
} | |
p.notice { | |
border: 1px solid rgb(255, 0, 0); | |
background-color: rgb(238, 238, 238); | |
color: rgb(0, 51, 102); | |
padding: 0.5em; | |
margin: 1em 2em 1em 1em; | |
} | |
</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="http://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 7.0.77, Mar 28 2017</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="http://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></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> | |
</blockquote></td></tr></table></td></tr><tr class="noPrint"><td width="20%" valign="top" nowrap class="noPrint"></td><td width="80%" valign="top" align="left"><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="comments_section" id="comments_section"><strong>Comments</strong></a></font></td></tr><tr><td><blockquote><p class="notice"><strong>Notice: </strong>This comments section collects your suggestions | |
on improving documentation for Apache Tomcat.<br><br> | |
If you have trouble and need help, read | |
<a href="http://tomcat.apache.org/findhelp.html">Find Help</a> page | |
and ask your question on the tomcat-users | |
<a href="http://tomcat.apache.org/lists.html">mailing list</a>. | |
Do not ask such questions here. This is not a Q&A section.<br><br> | |
The Apache Comments System is explained <a href="../comments.html">here</a>. | |
Comments may be removed by our moderators if they are either | |
implemented or considered invalid/off-topic.</p><script type="text/javascript"><!--//--><![CDATA[//><!-- | |
var comments_shortname = 'tomcat'; | |
var comments_identifier = 'http://tomcat.apache.org/tomcat-7.0-doc/config/loader.html'; | |
(function(w, d) { | |
if (w.location.hostname.toLowerCase() == "tomcat.apache.org") { | |
d.write('<div id="comments_thread"><\/div>'); | |
var s = d.createElement('script'); | |
s.type = 'text/javascript'; | |
s.async = true; | |
s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; | |
(d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); | |
} | |
else { | |
d.write('<div id="comments_thread"><strong>Comments are disabled for this page at the moment.<\/strong><\/div>'); | |
} | |
})(window, document); | |
//--><!]]></script></blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em> | |
Copyright © 1999-2017, Apache Software Foundation | |
</em></font></div></td></tr></table></body></html> |