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<h1 class="topictitle1"><span>About Tomcat</span></h1>
<div><p>This topic provides information about the Apache Software Foundation
Jakarta Tomcat servlet engine.</p>
<div class="important"><span class="importanttitle">Important:</span> Information
for this topic supports the latest PTF levels for HTTP Server for i5/OS .
It is recommended that you install the latest PTFs to upgrade to the latest
level of the HTTP Server for i5/OS. Some of the topics documented here are
not available prior to this update. See <a href="http://www-03.ibm.com/servers/eserver/iseries/software/http/services/service.html" target="_blank">http://www.ibm.com/servers/eserver/iseries/software/http/services/service.htm</a> <img src="www.gif" alt="Link outside Information Center" /> for more information. </div>
<p>The iSeries™ implementation
of Apache Software Foundation (ASF) Jakarta Tomcat servlet engine (hereafter
referred to as ASF Tomcat) provides a lightweight servlet engine that supports
servlets, JavaServer pages (JSPs), and Web application archive (WAR) files.
The HTTP Server for iSeries supports a module (mod_jk) that allows communication
between the HTTP Server (powered by Apache) and ASF Tomcat. </p>
<p>For more in-depth technical information about ASF Tomcat, see <a href="http://jakarta.apache.org/tomcat/index.html" target="_blank">http://jakarta.apache.org/tomcat/index.html</a> <img src="www.gif" alt="Link outside Information Center" />. For more in-depth
technical information about Java™ servlet technology (including the Java
Servlet Specification, V2.2), see<a href="http://java.sun.com/products/servlet/" target="_blank"> http://java.sun.com/products/servlet/</a> <img src="www.gif" alt="Link outside Information Center" />. </p>
<p>ASF Tomcat can be configured to run: </p>
<ul><li>In-process where ASF Tomcat and the HTTP Server (powered by Apache) run
in the same process and communicate through a Java native interface (JNI).
Generally, running in-process is easier to configure and gives better performance.
Running in-process also allows you to configure authentication through the
HTTP server (including the ability to swap to an authenticated user profile)
where out-of-process does not. </li>
<li>Out-of-process where ASF Tomcat runs in a separate process (this separate
process can be on a different computer than the HTTP server) and communicates
to the HTTP server through a TCP/IP sockets connection. It is important to
note that if SSL support is configured between the Web Browser and the Web
server, the connection between the Web server and the out-of-process ASF Tomcat
server is not secured with SSL. Running out-of-process allows more flexibility
in the number and type of processes that you can configure. An out-of-process
configuration allows for: <ul><li>application and functional isolation of information </li>
<li>reliability </li>
<li>serviceability </li>
<li>logically linking organizational synergies to application servlets <p>For
example, you may have different out-of-process ASF Tomcat servers on different
systems to service specific functional areas of an organization, like shipping
or accounting. </p>
</li>
</ul>
</li>
</ul>
<p>Configuration and administration of ASF Tomcat on the iSeries is accomplished
through the <span>IBM<sup>®</sup> Web Administration for i5/OS™ interface</span>. The
ASF Tomcat Basic wizard is provided as an easy way to get started configuring
servlets, JSPs, and WAR files. </p>
<p>ASF Tomcat supports the following: </p>
<ul><li>ASF Tomcat 3.2.4 </li>
<li>Java server pages (JSP) 1.1 </li>
<li>Servlet 2.2 specification </li>
<li>In-process ASF Tomcat </li>
<li>Out-of-process ASF Tomcat using mod_jk ajp12 protocol support </li>
<li>Out-of-process ASF Tomcat using mod_jk ajp13 protocol support </li>
<li>Making SSL certificates and attributes associated with the client request
available to the intended servlet, when configured as in-process or as out-of-process
using the ajp13 protocol </li>
<li>HTTP Server (powered by Apache) virtual host mapping to ASF Tomcat </li>
<li>JDK 1.2 and 1.3 </li>
</ul>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaieconcepts.htm" title="This topic provides concepts of functions on HTTP Server and IBM Web Administration for i5/OS interface.">Concepts of functions of HTTP Server</a></div>
</div>
</div><div class="nested1" id="directory"><a name="directory"><!-- --></a><h2 class="topictitle2">Directory structure</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" width="43.87755102040816%" id="d0e117">Directory</th>
<th valign="top" width="56.12244897959183%" id="d0e119">Description</th>
</tr>
</thead>
<tbody><tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>tomcat_home</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>The tomcat_home directory is the base directory for
ASF Tomcat. The tomcat_home directory can be located in the root or QOpenSys
file systems. For an in-process ASF Tomcat configuration, the default tomcat_home
directory is set to the HTTP server directory (/www/server_name/). For an
out-of-process ASF Tomcat configuration, the default tomcat-home directory
is set to /ASFTomcat/tomcat_server_name/. Within the tomcat_home directory
there are subdirectories for logs and configuration information.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>tomcat_home/webapps</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains WAR files if you have them.
All WAR files are expanded and subdirectories are added as contexts. </p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/webapps/ROOT</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory is required by ASF Tomcat.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/webapps/app1</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory is known as a document base directory.
You may have several document base directories under the webapps directory.
These represent and map a directory structure to a servlet or JSP application.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/webapps/app1/WEB-INF</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains the web.xml file for the
application.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/webapps/app1/WEB-INF/classes</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains any Java class files and
associated resources that are required for your application. This directory
is searched prior to the tomcat_home/webapps/app1/WEB-INF/lib directory for
any servlet .class file that is specified in the URL. </p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/webapps/app1/WEB-INF/lib</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains any JAR files and associated
resources that are required for your application.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/conf</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains the server.xml and workers.properties
configuration files.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/logs</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory contains all log files.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Tomcat_home/work</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory is automatically generated by ASF
Tomcat as a place to store intermediate files.</p>
</td>
</tr>
<tr><td valign="top" width="43.87755102040816%" headers="d0e117 "><p><tt>Java/lib</tt></p>
</td>
<td valign="top" width="56.12244897959183%" headers="d0e119 "><p>This directory is created as a place to put .jar
and Class files that you want to add to the class path.</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>See <a href="rzaiesetauth.htm">User profiles and required authorities for HTTP Server</a> for information
about authority considerations for ASF Tomcat.</p>
</div>
</div>
<div class="nested1" id="log"><a name="log"><!-- --></a><h2 class="topictitle2">Log files</h2>
<div><p>The jk.log file contains messages generated by <a href="rzaiemod_jk.htm">mod_jk</a>. It is important to note that this
file is not erased or regenerated when the ASF Tomcat engine starts. Messages
are appended to this file and the size of this file could grow very large
if errors are being logged. You should periodically monitor the size of this
file and reduce its size. By default, the jk.log is set to the logs directory
under server_home (<em>/www/server_name/logs/</em>). </p>
<p>Each time the ASF Tomcat servlet engine is started, a set of log files
is generated. These log files are all based on the configuration in the server.xml
file. The default location of the log files is in the <em>/logs</em> directory
under the tomcat_home directory. </p>
<p>The following is a description of each log file: </p>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" width="16.243654822335024%" id="d0e240">Log file</th>
<th valign="top" width="83.75634517766497%" id="d0e242">Description</th>
</tr>
</thead>
<tbody><tr><td valign="top" width="16.243654822335024%" headers="d0e240 "><p><tt>jasper.log</tt></p>
</td>
<td valign="top" width="83.75634517766497%" headers="d0e242 "><p>This log file contains messages resulting from trying
to start or run JSPs.</p>
</td>
</tr>
<tr><td valign="top" width="16.243654822335024%" headers="d0e240 "><p><tt>servlet.log</tt></p>
</td>
<td valign="top" width="83.75634517766497%" headers="d0e242 "><p>This log file contains messages generated as a result
of a servlet running in the ASF Tomcat servlet engine. When a servlet is initialized
a ServletConfig object is provided to the servlet. Contained within the ServletConfig
object is a ServletContext object that provides methods for a servlet to communicate
to the Servlet container, in this case Tomcat. On the ServletContext object
is a log method that allows Web applications to log to the servlet.log file.</p>
</td>
</tr>
<tr><td valign="top" width="16.243654822335024%" headers="d0e240 "><p><tt>tomcat.log</tt></p>
</td>
<td valign="top" width="83.75634517766497%" headers="d0e242 "><p>This log file contains ASF Tomcat servlet engine
messages.</p>
</td>
</tr>
<tr><td valign="top" width="16.243654822335024%" headers="d0e240 "><p><tt>jvmstderr.txt</tt></p>
</td>
<td valign="top" width="83.75634517766497%" headers="d0e242 "><p>This log file can contain messages from any Java
code that does a System.err.println().</p>
</td>
</tr>
<tr><td valign="top" width="16.243654822335024%" headers="d0e240 "><p><tt>jvmstdout.txt</tt></p>
</td>
<td valign="top" width="83.75634517766497%" headers="d0e242 "><p>This log file can contain messages from any Java
code that does a System.out.println().</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
<div class="nested1" id="process"><a name="process"><!-- --></a><h2 class="topictitle2">Process description</h2>
<div><p>Running in-process means that the ASF Tomcat module (mod_jk) uses the Java
invocation API to: </p>
<ul><li>Set up the JVM </li>
<li>Attach a given HTTP Server (powered by Apache) thread to the JVM </li>
<li>Run the servlet in the JVM </li>
</ul>
<p>The servlet, written in Java, uses the JNI interface to call to the HTTP
server to get the headers and data that accompany the HTTP request. The servlet
container invokes the target servlet, packages the response, and sends the
resulting response headers and data through the HTTP server using the JNI. </p>
<p>Running out-of-process means that the ASF Tomcat module (mod_jk) running
in the HTTP server needs to take the headers and accompanying data, package
it up into a protocol (ajp12 or ajp13), and then send that information across
a TCP socket to the system where the JVM is running. This could be on the
same system, or it could be on an different system. </p>
<p>The servlet running in the JVM does the following:</p>
<ul><li>Receives the request from the socket </li>
<li>Finds the target servlet </li>
<li>Invokes the target servlet </li>
<li>Packages the response headers and data into an ajp12 or ajp13 response
</li>
<li>Sends the response across the TCP socket to the HTTP server </li>
</ul>
<p>The ASF Tomcat module running in the HTTP Server decodes the ajp12 or ajp13
response to retrieve the HTTP headers and data. The ASF Tomcat module sends
the HTTP headers and data to the browser. </p>
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