| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 1 | <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">
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| 79 | </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="
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 80 | The Apache Tomcat Servlet/JSP Container
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 81 | " 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>
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| 82 | <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>
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 83 | </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>
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| 84 |
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| 85 | <p>The <strong>Loader</strong> element represents the <em>web
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| 86 | application class loader</em> that will be used to load Java
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| 87 | classes and resources for your web application. Such
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| 88 | a class loader must follow the requirements of the Servlet
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| 89 | Specification, and load classes from the following locations:</p>
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| 90 | <ul>
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| 91 | <li>From the <code>/WEB-INF/classes</code> directory inside your
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| 92 | web application.</li>
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| 93 | <li>From JAR files in the <code>/WEB-INF/lib</code> directory
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| 94 | inside your web application.</li>
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| 95 | <li>From resources made available by Catalina to all web
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| 96 | applications globally.</li>
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| 97 | </ul>
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| 98 |
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| 99 | <p>A Loader element MAY be nested inside a <a href="context.html">Context</a>
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| 100 | component. If it is not included, a default Loader configuration will be
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| 101 | created automatically, which is sufficient for most requirements.</p>
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| 102 |
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| 103 | <p>For a more in-depth description of the class loader hierarchy
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| 104 | that is implemented by Catalina, see <a href="../class-loader-howto.html">the ClassLoader HowTo</a>.</p>
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| 105 |
|
| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 106 | <p><em>The description below uses the variable name $CATALINA_BASE to refer the
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 107 | base directory against which most relative paths are resolved. If you have
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 108 | not configured Tomcat for multiple instances by setting a CATALINA_BASE
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 109 | directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 110 | the directory into which you have installed Tomcat.</em></p>
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 111 |
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| 112 | </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>
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| 113 |
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| 114 | <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>
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| 115 |
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| 116 | <p>All implementations of <strong>Loader</strong>
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| 117 | support the following attributes:</p>
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| 118 |
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 119 | <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">
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 120 | <p>Java class name of the implementation to use. This class must
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| 121 | implement the <code>org.apache.catalina.Loader</code> interface.
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| 122 | If not specified, the standard value (defined below) will be used.</p>
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 123 | </td></tr><tr><td align="left" valign="center"><code class="attributeName">delegate</code></td><td align="left" valign="center">
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 124 | <p>Set to <code>true</code> if you want the class loader to follow
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| 125 | the standard Java2 delegation model, and attempt to load classes from
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| 126 | parent class loaders <strong>before</strong> looking inside the web
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| 127 | application. Set to <code>false</code> (the default) to have the
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| 128 | class loader look inside the web application first, before asking
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| 129 | parent class loaders to find requested classes or resources.</p>
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 130 | </td></tr><tr><td align="left" valign="center"><code class="attributeName">reloadable</code></td><td align="left" valign="center">
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 131 | <p>Set to <code>true</code> if you want Catalina to monitor classes in
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| 132 | <code>/WEB-INF/classes/</code> and <code>/WEB-INF/lib</code> for
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| 133 | changes, and automatically reload the web application if a change
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| 134 | is detected. This feature is very useful during application
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| 135 | development, but it requires significant runtime overhead and is
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| 136 | not recommended for use on deployed production applications. You
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| 137 | can use the <a href="../manager-howto.html">Manager</a> web
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| 138 | application, however, to trigger reloads of deployed applications
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| 139 | on demand.</p>
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| 140 |
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| 141 | <p><strong>NOTE</strong> - The value for this property will be
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| 142 | inherited from the <code>reloadable</code> attribute you set on
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| 143 | the surrounding <a href="context.html">Context</a> component,
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| 144 | and any value you explicitly set here will be replaced.</p>
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| 145 | </td></tr></table>
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| 146 |
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| 147 | </blockquote></td></tr></table>
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| 148 |
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| 149 |
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| 150 | <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>
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| 151 |
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| 152 | <p>The standard implementation of <strong>Loader</strong> is
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| 153 | <strong>org.apache.catalina.loader.WebappLoader</strong>.
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| 154 | It supports the following additional attributes (in addition to the
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| 155 | common attributes listed above):</p>
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| 156 |
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 157 | <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">
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 158 | <p>Java class name of the <code>java.lang.ClassLoader</code>
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| 159 | implementation class to use. If not specified, the default value is
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| 160 | <code>org.apache.catalina.loader.WebappClassLoader</code>. Custom
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| 161 | <strong>loaderClass</strong> implementations must extend
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 162 | <code>org.apache.catalina.loader.WebappClassLoaderBase</code>.The
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| 163 | default <strong>loaderClass</strong> is not parallel capable. A parallel
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| 164 | capable <strong>loaderClass</strong> is available when running on a Java
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| 165 | 7 or higher JRE and can be used by specifying
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| 166 | <code>org.apache.catalina.loader.ParallelWebappClassLoader</code>.</p>
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| 167 | </td></tr><tr><td align="left" valign="center"><code class="attributeName">searchExternalFirst</code></td><td align="left" valign="center">
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 168 | <p>Set to <code>true</code> if you want repositories outside
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| 169 | of <code>WEB-INF/classes</code> and <code>WEB-INF/lib</code> to
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| 170 | be searched first. Default value is <code>false</code>.</p>
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| 171 | </td></tr></table>
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| 172 |
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| 173 | </blockquote></td></tr></table>
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| 174 |
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 175 | <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>
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| 176 |
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| 177 | <p>This implementation of <strong>Loader</strong> is
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| 178 | <strong>org.apache.catalina.loader.VirtualWebappLoader</strong>.
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| 179 | It extends <code>WebappLoader</code> and supports the following
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| 180 | additional attributes</p>
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| 181 |
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| 182 | <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">
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| 183 | <p>Additional repositories to search for resources.
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| 184 | Multiple values can be joined using <code>;</code>
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| 185 | as a separator.</p>
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| 186 | <p>Leading and trailing whitespaces in values are ignored.
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| 187 | If a value does not point to an existing directory or
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| 188 | <code>*.jar</code> file, it is silently skipped.
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| 189 | Diagnostic messages can be seen if you enable debug logging for
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| 190 | the VirtualWebappLoader class.
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| 191 | </p>
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| 192 | <p>Example: <code>virtualClasspath="${catalina.base}/myapp_config"</code></p>
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| 193 | </td></tr><tr><td align="left" valign="center"><code class="attributeName">searchVirtualFirst</code></td><td align="left" valign="center">
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| 194 | <p>Set to <code>true</code> if you want the virtual
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| 195 | class path to be searched before
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| 196 | <code>WEB-INF/classes</code> and <code>WEB-INF/lib</code>.
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| 197 | Default value is <code>false</code>.</p>
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| 198 | <p>If searched before, resources located in the virtual
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| 199 | class path take precendence over resources with the same
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| 200 | name contained in the webapp.</p>
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| 201 | </td></tr></table>
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| 202 |
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| 203 | </blockquote></td></tr></table>
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| 204 |
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 205 |
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| 206 | </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>
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| 207 |
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| 208 | <p>No components may be nested inside a <strong>Loader</strong> element.</p>
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| 209 |
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| 210 | </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>
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| 211 |
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| 212 | <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>
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| 213 |
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| 214 | <p>A loader is associated with the log category based on its classname.</p>
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| 215 |
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| 216 | </blockquote></td></tr></table>
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| 217 |
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| 刘洪青 | 6266f99 | 2017-05-15 21:21:03 +0800 | [diff] [blame^] | 218 | </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
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| 219 | on improving documentation for Apache Tomcat.<br><br>
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| 220 | If you have trouble and need help, read
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| 221 | <a href="http://tomcat.apache.org/findhelp.html">Find Help</a> page
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| 222 | and ask your question on the tomcat-users
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| 223 | <a href="http://tomcat.apache.org/lists.html">mailing list</a>.
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| 224 | Do not ask such questions here. This is not a Q&A section.<br><br>
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| 225 | The Apache Comments System is explained <a href="../comments.html">here</a>.
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| 226 | Comments may be removed by our moderators if they are either
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| 227 | implemented or considered invalid/off-topic.</p><script type="text/javascript"><!--//--><![CDATA[//><!--
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| 244 | Copyright © 1999-2017, Apache Software Foundation
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| Hongqing Liu | fd5ee81 | 2014-05-10 16:32:51 +0800 | [diff] [blame] | 245 | </em></font></div></td></tr></table></body></html> |