remm 2003/09/05 01:56:01
Modified: webapps/docs class-loader-howto.xml
Log:
- Classloader docs refresh.
Revision Changes Path
1.4 +40 -30 jakarta-tomcat-catalina/webapps/docs/class-loader-howto.xml
Index: class-loader-howto.xml
===================================================================
RCS file: /home/cvs/jakarta-tomcat-catalina/webapps/docs/class-loader-howto.xml,v
retrieving revision 1.3
retrieving revision 1.4
diff -u -r1.3 -r1.4
--- class-loader-howto.xml 15 Jan 2003 03:40:43 -0000 1.3
+++ class-loader-howto.xml 5 Sep 2003 08:56:01 -0000 1.4
@@ -111,19 +111,29 @@
are made visible through this
class loader. By default, that includes the following:
<ul>
- <li><em>jndi.jar</em> - The Java Naming and Directory Interface API
- classes (loaded <strong>ONLY</strong> on a JDK 1.2 system, because they
- are included automatically on JDK 1.3 and later).</li>
+ <li><em>ant.jar</em> - Apache Ant.</li>
+ <li><em>commons-collection.jar</em> - Jakarta commons collection.</li>
+ <li><em>commons-dbcp.jar</em> - Jakarta commons DBCP, providing a
+ JDBC connection pool to web applications.</li>
+ <li><em>commons-el.jar</em> - Jakarta commons el, implementing the
+ expression language used by Jasper.</li>
+ <li><em>commons-logging-api.jar</em> - Jakarta commons logging API.</li>
+ <li><em>commons-pool.jar</em> - Jakarta commons pool.</li>
+ <li><em>jasper-compiler.jar</em> - The JSP 2.0 compiler.</li>
+ <li><em>jasper-runtime.jar</em> - The JSP 2.0 runtime.</li>
+ <li><em>jmx.jar</em> - The JMX 1.2 implementation.</li>
+ <li><em>jsp-api.jar</em> - The JSP 2.0 API.</li>
<li><em>naming-common.jar</em> - The JNDI implementation used by Tomcat 5
to represent in-memory naming contexts.</li>
+ <li><em>naming-factory.jar</em> - The JNDI implementation used by Tomcat 5
+ to resolve references to enterprise resources (EJB, connection
+ pools).</li>
<li><em>naming-resources.jar</em> - The specialized JNDI naming context
implementation used to represent the static resources of a web
application.</li>
- <li><em>servlet.jar</em> - The Servlet and JSP API classes.</li>
+ <li><em>servlet-api.jar</em> - The Servlet and JSP API classes.</li>
<li><em>xerces.jar</em> - The XML parser that is visible by default to
- Tomcat internal classes and to web applications. This can be
- overridden, for a particular web application, by including your
- desired parser in <code>/WEB-INF/lib</code>.</li>
+ Tomcat internal classes and to web applications.</li>
</ul></li>
<li><strong>Catalina</strong> - This class loader is initialized to include
all classes and resources required to implement Tomcat 5 itself. These
@@ -148,18 +158,11 @@
<li><em>tomcat-coyote.jar</em> - Coyote connector for Tomcat 5.</li>
<li><em>tomcat-http11.jar</em> - Standalone Java HTTP/1.1
connector.</li>
- <li><em>tomcat-jk.jar</em> - Classes for the Java portion of the
- <code>JK</code> web server connector, which allows Tomcat to
- run behind web servers such as Apache and iPlanet iAS and iWS.</li>
<li><em>tomcat-jk2.jar</em> - Classes for the Java portion of the
<code>JK 2</code> web server connector, which allows Tomcat to
run behind web servers such as Apache and iPlanet iAS and iWS.</li>
<li><em>tomcat-util.jar</em> - Utility classes required by some
Tomcat connectors.</li>
- <li><em>tomcat-warp.jar</em> - Classes for the Java portion of the
- <code>Webapp</code> web server connector, using the WARP protocol
- which allows Tomcat to run behind the Apache HTTPD web server
- (1.3 and 2.0).</li>
</ul></li>
<li><strong>Shared</strong> - This class loader is the place to put classes
and resources that you wish to share across <strong>ALL</strong>
@@ -167,20 +170,11 @@
in which case you should put them in the <strong>Common</strong>
class loader instead). All unpacked classes and resources in
<code>$CATALINA_HOME/shared/classes</code>, as well as classes and
- resources in JAR files under <code>$CATALINA_HOME/lib</code>, are
- made visible through this class loader. By default, that includes
- the following:
- <ul>
- <li><em>jasper-compiler.jar</em> - The page compiler classes required
- to convert JSP source pages into executable servlets and compile
- them.</li>
- <li><em>jasper-runtime.jar</em> - The runtime support classes required
- to execute JSP pages that have already been translated into Java
- servlets and then compiled.</li>
- <li><em>naming-factory.jar</em> - JNDI object factories for resources
- supported by the default JNDI naming context provided to web
- applications.</li>
- </ul></li>
+ resources in JAR files under <code>$CATALINA_HOME/shared/lib</code>, are
+ made visible through this class loader. If multiple Tomcat instances are
+ run from the same binary using the $CATALINA_BASE environment variable,
+ then this classloader repositories are relative to $CATALINA_BASE rather
+ than $CATALINA_HOME.</li>
<li><strong>WebappX</strong> - A class loader is created for each web
application that is deployed in a single Tomcat 5 instance. All unpacked
classes and resources in the <code>/WEB-INF/classes</code> directory of
@@ -195,8 +189,24 @@
Servlet Specification, version 2.3, section 9.6). When a request to load a
class from the web application's <em>WebappX</em> class loader is processed,
this class loader will look in the local repositories <strong>first</strong>,
-instead of delegating before looking. All other class loaders in Tomcat 5
-follow the usual delegation pattern.</p>
+instead of delegating before looking. There are exceptions. Classes which are
+part of the JRE base classes cannot be overriden. For some classes (such as
+the XML parser components in JDK 1.4+), the JDK 1.4 endorsed feature can be
+used used
+(see the common classloader definition above). In addition, for the following
+class patterns, the classloader will always delegate first
+(and load the class itself if no parent classloader loads it):
+<ul>
+<li><em>javax.*</em></li>
+<li><em>org.xml.sax.*</em></li>
+<li><em>org.w3c.dom.*</em></li>
+<li><em>org.apache.commons.logging.*</em></li>
+<li><em>org.apache.xerces.*</em></li>
+<li><em>org.apache.xalan.*</em></li>
+</ul>
+Last, any JAR containing servlet API classes will be ignored by the
+classloader.
+All other class loaders in Tomcat 5 follow the usual delegation pattern.</p>
<p>Therefore, from the perspective of a web application, class or resource
loading looks in the following repositories, in this order:</p>
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