| <?xml version="1.0"?> |
| <!DOCTYPE document [ |
| <!ENTITY project SYSTEM "project.xml"> |
| ]> |
| <document url="loader.html"> |
| |
| &project; |
| |
| <properties> |
| <author email="craigmcc@apache.org">Craig R. McClanahan</author> |
| <title>The Loader Component</title> |
| </properties> |
| |
| <body> |
| |
| |
| <section name="Introduction"> |
| |
| <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 <strong>FIXME - Reference</strong>.</p> |
| |
| <blockquote><em> |
| <p>The description below uses the variable name $CATALINA_HOME |
| to refer to the directory into which you have installed Tomcat 5, |
| and is the base directory against which most relative paths are |
| resolved. However, if you have configured Tomcat 5 for multiple |
| instances by setting a CATALINA_BASE directory, you should use |
| $CATALINA_BASE instead of $CATALINA_HOME for each of these |
| references.</p> |
| </em></blockquote> |
| |
| </section> |
| |
| |
| <section name="Attributes"> |
| |
| <subsection name="Common Attributes"> |
| |
| <p>All implementations of <strong>Loader</strong> |
| support the following attributes:</p> |
| |
| <attributes> |
| |
| <attribute name="className" required="false"> |
| <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> |
| </attribute> |
| |
| <attribute name="delegate" required="false"> |
| <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> |
| </attribute> |
| |
| <attribute name="reloadable" required="false"> |
| <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> |
| </attribute> |
| |
| </attributes> |
| |
| </subsection> |
| |
| |
| <subsection name="Standard Implementation"> |
| |
| <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> |
| |
| <attributes> |
| |
| <attribute name="checkInterval" required="false"> |
| <p>The number of seconds between checks for modified classes and |
| resources, if <code>reloadable</code> has been set to |
| <code>true</code>. The default is 15 seconds.</p> |
| </attribute> |
| |
| <attribute name="debug" required="false"> |
| <p>The level of debugging detail logged by this <strong>Engine</strong> |
| to the associated <a href="logger.html">Logger</a>. Higher numbers |
| generate more detailed output. If not specified, the default |
| debugging detail level is zero (0).</p> |
| </attribute> |
| |
| <attribute name="loaderClass" required="false"> |
| <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>.</p> |
| </attribute> |
| |
| </attributes> |
| |
| </subsection> |
| |
| |
| </section> |
| |
| |
| <section name="Nested Components"> |
| |
| <p>No components may be nested inside a <strong>Loader</strong> element.</p> |
| |
| </section> |
| |
| |
| <section name="Special Features"> |
| |
| <p>No special features are associated with a <strong>Loader</strong> |
| element.</p> |
| |
| </section> |
| |
| |
| </body> |
| |
| |
| </document> |
