108 lines
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108 lines
8.8 KiB
HTML
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<html lang="en"><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><link href="../images/docs-stylesheet.css" rel="stylesheet" type="text/css"><title>Apache Tomcat 11 Configuration Reference (11.0.1) - The Loader Component</title><meta name="author" content="Craig R. McClanahan"></head><body><div id="wrapper"><header><div id="header"><div><div><div class="logo noPrint"><a href="https://tomcat.apache.org/"><img alt="Tomcat Home" src="../images/tomcat.png"></a></div><div style="height: 1px;"></div><div class="asfLogo noPrint"><a href="https://www.apache.org/" target="_blank"><img src="../images/asf-logo.svg" alt="The Apache Software Foundation" style="width: 266px; height: 83px;"></a></div><h1>Apache Tomcat 11 Configuration Reference</h1><div class="versionInfo">
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Version 11.0.1,
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<time datetime="2024-11-06">Nov 6 2024</time></div><div style="height: 1px;"></div><div style="clear: left;"></div></div></div></div></header><div id="middle"><div><div id="mainLeft" class="noprint"><div><nav><div><h2>Links</h2><ul><li><a href="../index.html">Docs Home</a></li><li><a href="index.html">Config Ref. Home</a></li><li><a href="https://cwiki.apache.org/confluence/display/TOMCAT/FAQ">FAQ</a></li><li><a href="#comments_section">User Comments</a></li></ul></div><div><h2>Top Level Elements</h2><ul><li><a href="server.html">Server</a></li><li><a href="service.html">Service</a></li></ul></div><div><h2>Executors</h2><ul><li><a href="executor.html">Executor</a></li></ul></div><div><h2>Connectors</h2><ul><li><a href="http.html">HTTP/1.1</a></li><li><a href="http2.html">HTTP/2</a></li><li><a href="ajp.html">AJP</a></li></ul></div><div><h2>Containers</h2><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></div><div><h2>Nested Components</h2><ul><li><a href="cookie-processor.html">CookieProcessor</a></li><li><a href="credentialhandler.html">CredentialHandler</a></li><li><a href="globalresources.html">Global Resources</a></li><li><a href="jar-scanner.html">JarScanner</a></li><li><a href="jar-scan-filter.html">JarScanFilter</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></div><div><h2>Cluster Elements</h2><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></div><div><h2>web.xml</h2><ul><li><a href="filter.html">Filter</a></li></ul></div><div><h2>Other</h2><ul><li><a href="systemprops.html">System properties</a></li><li><a href="jaspic.html">Jakarta Authentication</a></li></ul></div></nav></div></div><div id="mainRight"><div id="content"><h2>The Loader Component</h2><h3 id="Table_of_Contents">Table of Contents</h3><div class="text">
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<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></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>
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</div><h3 id="Introduction">Introduction</h3><div class="text">
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<p>The <strong>Loader</strong> element represents the <em>web
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application class loader</em> that will be used to load Java
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classes and resources for your web application. Such
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a class loader must follow the requirements of the Servlet
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Specification, and load classes from the following locations:</p>
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<ul>
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<li>From the <code>/WEB-INF/classes</code> directory inside your
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web application.</li>
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<li>From JAR files in the <code>/WEB-INF/lib</code> directory
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inside your web application.</li>
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<li>From resources made available by Catalina to all web
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applications globally.</li>
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</ul>
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<p>A Loader element MAY be nested inside a <a href="context.html">Context</a>
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component. If it is not included, a default Loader configuration will be
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created automatically, which is sufficient for most requirements.</p>
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<p>For a more in-depth description of the class loader hierarchy
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that is implemented by Catalina, see <a href="../class-loader-howto.html">the ClassLoader HowTo</a>.</p>
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<p><em>The description below uses the variable name $CATALINA_BASE to refer the
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base directory against which most relative paths are resolved. If you have
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not configured Tomcat for multiple instances by setting a CATALINA_BASE
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directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
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the directory into which you have installed Tomcat.</em></p>
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</div><h3 id="Attributes">Attributes</h3><div class="text">
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<div class="subsection"><h4 id="Common_Attributes">Common Attributes</h4><div class="text">
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<p>All implementations of <strong>Loader</strong>
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support the following attributes:</p>
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<table class="defaultTable"><tr><th style="width: 15%;">
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Attribute
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</th><th style="width: 85%;">
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Description
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</th></tr><tr id="Attributes_Common Attributes_className"><td><code class="attributeName">className</code></td><td>
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<p>Java class name of the implementation to use. This class must
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implement the <code>org.apache.catalina.Loader</code> interface.
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If not specified, the standard value (defined below) will be used.</p>
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</td></tr><tr id="Attributes_Common Attributes_delegate"><td><code class="attributeName">delegate</code></td><td>
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<p>Set to <code>true</code> if you want the class loader to follow
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the standard Java2 delegation model, and attempt to load classes from
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parent class loaders <strong>before</strong> looking inside the web
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application. Set to <code>false</code> (the default) to have the
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class loader look inside the web application first, before asking
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parent class loaders to find requested classes or resources.</p>
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</td></tr></table>
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</div></div>
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<div class="subsection"><h4 id="Standard_Implementation">Standard Implementation</h4><div class="text">
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<p>The standard implementation of <strong>Loader</strong> is
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<strong>org.apache.catalina.loader.WebappLoader</strong>.
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It supports the following additional attributes (in addition to the
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common attributes listed above):</p>
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<table class="defaultTable"><tr><th style="width: 15%;">
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Attribute
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</th><th style="width: 85%;">
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Description
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</th></tr><tr id="Attributes_Standard Implementation_loaderClass"><td><code class="attributeName">loaderClass</code></td><td>
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<p>Java class name of the <code>java.lang.ClassLoader</code>
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implementation class to use. Custom implementations must extend
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<code>org.apache.catalina.loader.WebappClassLoaderBase</code>.
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</p>
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<p>If not specified, the default value is
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<code>org.apache.catalina.loader.ParallelWebappClassLoader</code>. The
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default <strong>loaderClass</strong> is parallel capable, which
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means that multiple threads may load difference classes in parallel.
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A non-parallel capable <strong>loaderClass</strong> is available and can
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be used by specifying
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<code>org.apache.catalina.loader.WebappClassLoader</code>.</p>
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</td></tr></table>
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</div></div>
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</div><h3 id="Nested_Components">Nested Components</h3><div class="text">
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<p>No components may be nested inside a <strong>Loader</strong> element.</p>
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</div><h3 id="Special_Features">Special Features</h3><div class="text">
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<div class="subsection"><h4 id="Logging">Logging</h4><div class="text">
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<p>A loader is associated with the log category based on its classname.</p>
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</div></div>
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</div></div></div></div></div><footer><div id="footer">
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<br>
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Apache Tomcat, Tomcat, Apache, the Apache Tomcat logo and the Apache logo
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are either registered trademarks or trademarks of the Apache Software
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Foundation.
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