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| 771 | blopes | 1 | <!DOCTYPE html SYSTEM "about:legacy-compat"> |
| 2 | <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 9 Configuration Reference (9.0.112) - The Loader Component</title></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 9 Configuration Reference</h1><div class="versionInfo"> |
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| 3 | Version 9.0.112, |
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| 4 | <time datetime="2025-11-06">Nov 6 2025</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="runtime-attributes.html">Runtime attributes</a></li><li><a href="systemprops.html">System properties</a></li><li><a href="jaspic.html">JASPIC</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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| 5 | <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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| 6 | </div><h3 id="Introduction">Introduction</h3><div class="text"> |
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| 7 | |||
| 8 | <p>The <strong>Loader</strong> element represents the <em>web |
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| 9 | application class loader</em> that will be used to load Java |
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| 10 | classes and resources for your web application. Such |
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| 11 | a class loader must follow the requirements of the Servlet |
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| 12 | Specification, and load classes from the following locations:</p> |
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| 13 | <ul> |
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| 14 | <li>From the <code>/WEB-INF/classes</code> directory inside your |
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| 15 | web application.</li> |
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| 16 | <li>From JAR files in the <code>/WEB-INF/lib</code> directory |
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| 17 | inside your web application.</li> |
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| 18 | <li>From resources made available by Catalina to all web |
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| 19 | applications globally.</li> |
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| 20 | </ul> |
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| 21 | |||
| 22 | <p>A Loader element MAY be nested inside a <a href="context.html">Context</a> |
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| 23 | component. If it is not included, a default Loader configuration will be |
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| 24 | created automatically, which is sufficient for most requirements.</p> |
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| 25 | |||
| 26 | <p>For a more in-depth description of the class loader hierarchy |
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| 27 | that is implemented by Catalina, see <a href="../class-loader-howto.html">the ClassLoader HowTo</a>.</p> |
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| 28 | |||
| 29 | <p><em>The description below uses the variable name $CATALINA_BASE to refer the |
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| 30 | base directory against which most relative paths are resolved. If you have |
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| 31 | not configured Tomcat for multiple instances by setting a CATALINA_BASE |
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| 32 | directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME, |
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| 33 | the directory into which you have installed Tomcat.</em></p> |
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| 34 | |||
| 35 | </div><h3 id="Attributes">Attributes</h3><div class="text"> |
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| 36 | |||
| 37 | <div class="subsection"><h4 id="Common_Attributes">Common Attributes</h4><div class="text"> |
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| 38 | |||
| 39 | <p>All implementations of <strong>Loader</strong> |
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| 40 | support the following attributes:</p> |
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| 41 | |||
| 42 | <table class="defaultTable"><tr><th style="width: 15%;"> |
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| 43 | Attribute |
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| 44 | </th><th style="width: 85%;"> |
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| 45 | Description |
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| 46 | </th></tr><tr id="Attributes_Common Attributes_className"><td><code class="attributeName">className</code></td><td> |
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| 47 | <p>Java class name of the implementation to use. This class must |
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| 48 | implement the <code>org.apache.catalina.Loader</code> interface. |
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| 49 | If not specified, the standard value (defined below) will be used.</p> |
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| 50 | </td></tr><tr id="Attributes_Common Attributes_delegate"><td><code class="attributeName">delegate</code></td><td> |
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| 51 | <p>Set to <code>true</code> if you want the class loader to follow |
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| 52 | the standard Java2 delegation model, and attempt to load classes from |
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| 53 | parent class loaders <strong>before</strong> looking inside the web |
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| 54 | application. Set to <code>false</code> (the default) to have the |
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| 55 | class loader look inside the web application first, before asking |
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| 56 | parent class loaders to find requested classes or resources.</p> |
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| 57 | </td></tr><tr id="Attributes_Common Attributes_reloadable"><td><code class="attributeName">reloadable</code></td><td> |
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| 58 | <p><strong>NOTE</strong> - This attribute has been deprecated in Tomcat |
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| 59 | 9 and will be removed in Tomcat 10. Use the equivalent attribute on the |
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| 60 | surrounding <a href="context.html">Context</a> component.</p> |
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| 61 | |||
| 62 | <p>Set to <code>true</code> if you want Catalina to monitor classes in |
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| 63 | <code>/WEB-INF/classes/</code> and <code>/WEB-INF/lib</code> for |
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| 64 | changes, and automatically reload the web application if a change |
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| 65 | is detected. This feature is very useful during application |
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| 66 | development, but it requires significant runtime overhead and is |
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| 67 | not recommended for use on deployed production applications. You |
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| 68 | can use the <a href="../manager-howto.html">Manager</a> web |
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| 69 | application, however, to trigger reloads of deployed applications |
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| 70 | on demand.</p> |
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| 71 | |||
| 72 | <p><strong>NOTE</strong> - The value for this property will be |
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| 73 | inherited from the <code>reloadable</code> attribute you set on |
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| 74 | the surrounding <a href="context.html">Context</a> component, |
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| 75 | and any value you explicitly set here will be replaced.</p> |
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| 76 | </td></tr></table> |
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| 77 | |||
| 78 | </div></div> |
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| 79 | |||
| 80 | |||
| 81 | <div class="subsection"><h4 id="Standard_Implementation">Standard Implementation</h4><div class="text"> |
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| 82 | |||
| 83 | <p>The standard implementation of <strong>Loader</strong> is |
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| 84 | <strong>org.apache.catalina.loader.WebappLoader</strong>. |
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| 85 | It supports the following additional attributes (in addition to the |
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| 86 | common attributes listed above):</p> |
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| 87 | |||
| 88 | <table class="defaultTable"><tr><th style="width: 15%;"> |
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| 89 | Attribute |
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| 90 | </th><th style="width: 85%;"> |
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| 91 | Description |
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| 92 | </th></tr><tr id="Attributes_Standard Implementation_loaderClass"><td><code class="attributeName">loaderClass</code></td><td> |
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| 93 | <p>Java class name of the <code>java.lang.ClassLoader</code> |
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| 94 | implementation class to use. Custom implementations must extend |
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| 95 | <code>org.apache.catalina.loader.WebappClassLoaderBase</code>. |
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| 96 | </p> |
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| 97 | |||
| 98 | <p>If not specified, the default value is |
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| 99 | <code>org.apache.catalina.loader.ParallelWebappClassLoader</code>. The |
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| 100 | default <strong>loaderClass</strong> is parallel capable, which |
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| 101 | means that multiple threads may load difference classes in parallel. |
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| 102 | A non-parallel capable <strong>loaderClass</strong> is available and can |
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| 103 | be used by specifying |
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| 104 | <code>org.apache.catalina.loader.WebappClassLoader</code>.</p> |
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| 105 | </td></tr></table> |
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| 106 | |||
| 107 | </div></div> |
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| 108 | |||
| 109 | </div><h3 id="Nested_Components">Nested Components</h3><div class="text"> |
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| 110 | |||
| 111 | <p>No components may be nested inside a <strong>Loader</strong> element.</p> |
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| 112 | |||
| 113 | </div><h3 id="Special_Features">Special Features</h3><div class="text"> |
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| 114 | |||
| 115 | <div class="subsection"><h4 id="Logging">Logging</h4><div class="text"> |
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| 116 | |||
| 117 | <p>A loader is associated with the log category based on its classname.</p> |
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| 118 | |||
| 119 | </div></div> |
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| 120 | |||
| 121 | </div></div></div></div></div><footer><div id="footer"> |
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| 122 | Copyright © 1999-2025, The Apache Software Foundation |
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| 123 | <br> |
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| 124 | Apache Tomcat, Tomcat, Apache, the Apache Tomcat logo and the Apache logo |
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| 125 | are either registered trademarks or trademarks of the Apache Software |
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| 126 | Foundation. |
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| 127 | </div></footer></div></body></html> |