connectors/jk/xdocs/index.xml

<?xml version="1.0"?>
<document>
<copyright>
   Copyright 1999-2004 The Apache Software Foundation
 
   Licensed 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
 
       http://www.apache.org/licenses/LICENSE-2.0
 
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
</copyright>
<properties>
<title>Overview</title>
<author email="jfrederic.clere@fujitsu-siemens.com">Jean-Frederic Clere</author>
<author email="hgomez@apache.org">Henri Gomez</author>
<author email="yoavs@apache.org">Yoav Shapira</author>
<date>$Date$</date>
</properties>

<section name="What's JK&#63;">
<p>
<b>JK</b> is a replacement to the elderly mod_jserv. 
It was a completely new Tomcat-Apache plug-in that handles the communication between Tomcat and Apache.
</p>
<p>
The newest <b>JK2</b> is a refactoring of <b>JK</b>.
The native part has been completly
restructured and the configuration has been simplified a lot.
</p>

<p>
JK is more than just an apache module, since it could be used with majors WebServer :
</p>

<ul>
<li>
<a href="jk/aphowto.html">mod_jk</a> is an Apache module to be used with <b>Apache 1.3</b> and <b>2.0</b> Webservers.
</li>
<li>
<a href="jk/iishowto.html">isapi</a> is a redirector to be used with <b>IIS</b>.
</li>
<li>
<a href="jk/neshowto.html">nsapi</a> is a redirector to be used with <b>Netscape/iPlanet</b>.
</li>
<li>
<a href="jk/domhowto.html">dsapi</a> is a redirector to to be used with <b>Domino</b>.
</li>
</ul>

</section>

<section name="Why should I use the JK&#63;">
<p>
JK was develop to overcome many limitations of its ancestor, <b>mod_jserv</b>.
</p>

<p>
<b>mod_jserv</b> was too complex and because it was ported from Apache/JServ, 
it brought with it lots of JServ specific bits that aren't needed by Apache.
</p>

<p>
Where <b>mod_jserv</b> supported only Apache webservers on Unix OS, 
<b>JK</b> supports much more web servers and operating systems through 
via a compatibility layer named the <b>JK library</b>. 
The layered approach provided by the JK library makes it easier to 
support many different webservers and OS.
</p>

<p>
JK offer better support for SSL, that's was a problem with mod_jserv which couldn't 
reliably identify whether a request was made via HTTP or HTTPS. 
</p>
<p>
JK can, using the newer Ajpv13 protocol which relay many SSL informations required by servlet 2.2 and 2.3 specs.
</p>

<p>
JK offers a lot of different and flexible communications between a Web Server 
and the Tomcat Servlet Engine and could be used today with all of the ASF Tomcat Engines, 
<b>3.2.x</b>, <b>3.3.x</b>, <b>4.0.x</b>, <b>4.1.x</b> and <b>5.x</b>
</p>

</section>

<section name="What's the difference between JK and JK2&#63;">
<p>
JK2 is a refactoring of JK and is much more powerfull.
</p>
<p>
Even if it works with Apache 1.3, JK2 has been developed with Apache 2.0 in mind,
and is better suited for multi-threaded servers like IIS, NES/iPlanet. It can also
be embeded in other applications and used from java.
</p>
<p>
JK2 improves the modularity and has a better separation between protocol and physical layer.
As such JK2 support fast unix-socket, and could be extended to support others communications
channels. It is better suited for JNI and may use (in a future version) JDK 1.4 NIO.
</p>
<p>
There is additional support for monitoring, similar with JMX in java. A module similar
with mod_status is provided, and additional adapters can be used to interface and 
provide status and runtime configuration. .
</p>
<p>
The configuration has been changed to follow the component models. Multiple configuration
sources can be supported ( in additon to file ) providing better integration with
the embeding application. The config layer uses the management layer APIs and it can
support persistence for changes done via runtime configuration.
</p>
<p>
Another feature is the JNI mode. Jk2 can be used as a JNI library and provide access to
native features to java. For example it provides access to shared memory ( used for 
config and monitoring in a multiprocess environment ), unix domain sockets. It can
also provide access to signals, chuid, win registry. All using the same communication
mechansim, and supporting both in-process and out-of process modes.
</p>
</section>


<section name="Are there alternative ways to connect Apache and Tomcat&#63;">
<p>
<b>Tomcat's internal HTTP stack and mod_proxy</b> which is not that bad, but slow,
well, of course Tomcat didn't have 10/11 years of C routine optimization like
the Apache Web Server, but it's quite good. The only disadvantage is that it
looks pretty ridiculous to parse an HTTP request to generate it again
(exactly the same), and to parse again the response to send it back unchanged...
</p>
<p>
<a href="http://jakarta.apache.org/~jfclere/webapp_docs/">mod_webapp</a> which is very easy to configure, has a well defined protocol named
<a href="http://jakarta.apache.org/~jfclere/webapp_docs/warp.html">WARP</a> but it is no longer developped.
BTW: It would be possible to implement the <b>WARP</b> protocol in
<b>JK2</b> ;-))
</p>
</section>

<section name="Additional References">
<p>
Please note that we maintain a list of references to external documentation
on connector usage and configuration in various environments as part of
the Tomcat wiki <a href="http://wiki.apache.org/jakarta-tomcat/Tomcat_2fLinks">Useful Links</a> page.
</p>
</section>

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