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Tomcat example source code file (RELEASE-NOTES)

This example Tomcat source code file (RELEASE-NOTES) is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The Tomcat RELEASE-NOTES source code

  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  See the License for the specific language governing permissions and
  limitations under the License.

$Id: RELEASE-NOTES 612940 2008-01-17 19:22:26Z markt $

                     Apache Tomcat Version @VERSION@
                            Release Notes


* Dependency Changes
* JNI Based Applications
* Bundled APIs
* Web application reloading and static fields in shared libraries
* Tomcat on Linux
* Enabling SSI and CGI Support
* Security manager URLs
* Symlinking static resources
* Enabling invoker servlet
* Viewing the Tomcat Change Log
* When all else fails

Dependency Changes:
Tomcat 6.0 is designed to run on JSE 5.0 and later.

In addition, Tomcat 6.0 uses the Eclipse JDT Java compiler for compiling
JSP pages.  This means you no longer need to have the complete
Java Development Kit (JDK) to run Tomcat, but a Java Runtime Environment
(JRE) is sufficient.  The Eclipse JDT Java compiler is bundled with the 
binary Tomcat distributions.  Tomcat can also be configured to use the
compiler from the JDK to compile JSPs, or any other Java compiler supported 
by Apache Ant.

JNI Based Applications:
Applications that require native libraries must ensure that the libraries have
been loaded prior to use.  Typically, this is done with a call like:

  static {

in some class.  However, the application must also ensure that the library is
not loaded more than once.  If the above code were placed in a class inside
the web application (i.e. under /WEB-INF/classes or /WEB-INF/lib), and the
application were reloaded, the loadLibrary() call would be attempted a second

To avoid this problem, place classes that load native libraries outside of the
web application, and ensure that the loadLibrary() call is executed only once
during the lifetime of a particular JVM.

Bundled APIs:
A standard installation of Tomcat 6.0 makes all of the following APIs available
for use by web applications (by placing them in "lib"):
* annotations-api.jar (Annotations package)
* catalina.jar (Tomcat Catalina implementation)
* catalina-ant.jar (Tomcat Catalina Ant tasks)
* catalina-ha.jar (High availability package)
* catalina-tribes.jar (Group communication)
* el-api.jar (EL 2.1 API)
* jasper.jar (Jasper 2 Compiler and Runtime)
* jasper-el.jar (Jasper 2 EL implementation)
* jasper-jdt.jar (Eclipse JDT 3.3 Java compiler)
* jsp-api.jar (JSP 2.1 API)
* servlet-api.jar (Servlet 2.5 API)
* tomcat-coyote.jar (Tomcat connectors and utility classes)
* tomcat-dbcp.jar (package renamed database connection pool based on Commons DBCP)

You can make additional APIs available to all of your web applications by
putting unpacked classes into a "classes" directory (not created by default),
or by placing them in JAR files in the "lib" directory.

To override the XML parser implementation or interfaces, use the endorsed
mechanism of the JVM. The default configuration defines JARs located in 
"endorsed" as endorsed.

Web application reloading and static fields in shared libraries:
Some shared libraries (many are part of the JDK) keep references to objects
instantiated by the web application. To avoid class loading related problems
(ClassCastExceptions, messages indicating that the classloader
is stopped, etc.), the shared libraries state should be reinitialized.

Something which might help is to avoid putting classes which would be
referenced by a shared static field in the web application classloader,
and putting them in the shared classloader instead (JARs should be put in the
"lib" folder, and classes should be put in the "classes" folder).

Tomcat on Linux:
GLIBC 2.2 / Linux 2.4 users should define an environment variable:
export LD_ASSUME_KERNEL=2.2.5

Redhat Linux 9.0 users should use the following setting to avoid
stability problems:
export LD_ASSUME_KERNEL=2.4.1

There are some Linux bugs reported against the NIO sendfile behavior, make sure you
have a JDK that is up to date, or disable sendfile behavior in the Connector.<br/>
6427312: (fc) FileChannel.transferTo() throws IOException "system call interrupted"<br/>
5103988: (fc) FileChannel.transferTo should return -1 for EAGAIN instead throws IOException<br/>
6253145: (fc) FileChannel.transferTo on Linux fails when going beyond 2GB boundary<br/>
6470086: (fc) FileChannel.transferTo(2147483647, 1, channel) cause "Value too large" exception<br/>

Enabling SSI and CGI Support:
Because of the security risks associated with CGI and SSI available
to web applications, these features are disabled by default.  

To enable and configure CGI support, please see the cgi-howto.html page.

To enable and configue SSI support, please see the ssi-howto.html page.

Security manager URLs:
In order to grant security permissions to JARs located inside the
web application repository, use URLs of of the following format
in your policy file:


Symlinking static resources:
By default, Unix symlinks will not work when used in a web application to link
resources located outside the web application root directory.

This behavior is optional, and the "allowLinking" flag may be used to disable
the check.

Enabling invoker servlet:
Starting with Tomcat 4.1.12, the invoker servlet is no longer available by
default in all webapps. Enabling it for all webapps is possible by editing
$CATALINA_HOME/conf/web.xml to uncomment the "/servlet/*" servlet-mapping

Using the invoker servlet in a production environment is not recommended and
is unsupported.  More details are available on the Tomcat FAQ at

Viewing the Tomcat Change Log:
See changelog.html in this directory.

When all else fails:
See the FAQ

Other Tomcat examples (source code examples)

Here is a short list of links related to this Tomcat RELEASE-NOTES source code file:

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