Apache Tomcat :: Apache Software Foundation

The Apache Tomcat Connector - Webserver HowTo

SunOne -- Netscape/iPlanet HowTo

Introduction

This document explains how to set up Sun ONE Web Server previously known as Netscape web servers to cooperate with Tomcat.

Normally the Sun ONE Web Servers come with their own Servlet engine, but you can also configure them to send servlet and JSP requests to Tomcat using the NSAPI redirector plugin.

It is recommended that you also read the Workers HowTo document to learn how to setup the working entities between your web server and Tomcat Engines.

Document Conventions and Assumptions

${tomcat_home} is the root directory of tomcat. Your Tomcat installation should have the following subdirectories:

  • ${tomcat_home}\conf - Where you can place various configuration files
  • ${tomcat_home}\webapps - Containing example applications
  • ${tomcat_home}\bin - Where you place web server plugins

In all the examples in this document ${tomcat_home} will be c:\tomcat. A worker is defined to be a tomcat process that accepts work from the Sun ONE Web Server.

Supported Configuration

The NSAPI-Tomcat redirector was developed and tested on:

  • WINNT 2000/XP/2003 (should be able to work with other service packs) and some Unixes
  • Sun ONE Web Server 6.1
  • Tomcat 4.1 to Tomcat 8.

The redirector uses ajp12 and ajp13 to send requests to the Tomcat containers. There is also an option to use Tomcat in process, more about the in-process mode can be found in the in process howto.

Who support ajp protocols ?

The ajp12 protocol is only available in Tomcat 3.2.x and 3.3.x.

The ajp12 has been deprecated with Tomcat 3.3.x and you should use instead ajp13 which is the only ajp protocol known by Tomcat 4 and above.

Of course Tomcat 3.2.x and 3.3.x also support ajp13 protocol.

Others servlet engines such as jetty have support for ajp13 protocol

How does it work ?

  1. The NSAPI-Tomcat redirector is an Netscape service step plugin, Netscape load the redirector plugin and calls its service handler function for request that are assigned to the "servlet" configuration object.
  2. For each in-coming request Netscape will execute the set of NameTrans directives that we added to obj.conf, the assign-name function will check if it's from parameter matches the request URL.
  3. If a match is found, assign-name will assign the servlet object name to the request. This will cause Netscape to send the request to the servlet configuration object.
  4. Netscape will execute our jk_service extension. The extension collects the request parameters and forwards them to the appropriate worker using the ajp13 protocol (the worker="defworker" parameter in jk_service inform it that the worker for this request is named defworker). the workers properties files, workers.properties, will indicate that defworker use ajp13 protocol.
  5. The extension collects the response from the worker and returns it to the browser.

Installation

A pre-built version of the NSAPI redirector, nsapi_redirect.dll, may be available under the win32/i386 directory of tomcat-connectors distribution. For those using Netscape as your browser, try downloading a zip version of the file, if available. You can also build a copy locally from the source present in tomcat-connectors distribution. The Tomcat redirector requires two entities:

  • nsapi_redirect.dll (Windows) -or- nsapi_redirector.so (Unix) - The NSAPI server plugin, either obtain a pre-built DLL/so or build it yourself (see the build section).
  • workers.properties - A file that describes the host(s) and port(s) used by the workers (Tomcat processes). A sample workers.properties can be found under the conf directory.
The installation includes the following parts:
  • Configuring the NSAPI redirector with a default /examples context and checking that you can serve servlets with Netscape.
  • Adding more contexts to the configuration.

Configuring the NSAPI Redirector

In this document we'll assume that nsapi_redirect.dll is placed in c:\jk\lib\nsapi_redirect.dll, the properties file is inc:\jk\conf and you created a log directory c:\jk\logs

  • If the built in servlet support is working disable it.
  • Add the redirector plugin into the Netscape server configuration. Edit your server magnus.conf and add the following lines:
  
  Init fn="load-modules" funcs="jk_init,jk_service" shlib="c:/jk/lib/nsapi_redirect.dll" shlib_flags="(global|now)"
  Init fn="jk_init" worker_file="c:/jk/conf/workers.properties" log_level="debug" log_file="c:/jk/logs/nsapi.log" shm_file="c:/jk/logs/jk_shm"
  • Edit your server obj.conf and add the following lines:

  
  In the default object NameTrans section
  <Object name="default">
      
  NameTrans fn="assign-name" from="/servlets-examples(|/*)" name="jknsapi" 
  NameTrans fn="assign-name" from="/jsp-examples(|/*)" name="jknsapi"
  ....
  </Object>
  
  Create a new configuration object by adding the following lines to the end of the obj.conf file
  
  <Object name="jknsapi">
  ObjectType fn=force-type type=text/plain
  Service fn="jk_service" method="*" worker="worker1"
  </Object>
  • Edit your worker definition file workers.properties. You should at least choose a connection pool size:
  #An entry that lists all the workers defined. For example:
  worker.list=worker1
  
  # Entries that define the host and port associated with these workers.
  worker.worker1.host=localhost
  worker.worker1.port=8009
  worker.worker1.type=ajp13
  worker.worker1.connection_pool_size=50
  • Restart Web Server (stop and start the server)

That's all, now you should start tomcat and ask for http://server:port/servlets-examples/

The file obj.conf seems to be sensitive to leading white space in lines, especially in the Object element. Make sure you have no leading white space (no indentation) on any line of this file.

Adding additional Contexts

The examples context is useful for verifying your installation, but you will also need to add your own contexts. Adding a new context requires two operations:

  • Adding the context to Tomcat (I am not going to talk about this).
  • Assigning the NSAPI redirector to handle this context.

Assigning the NSAPI redirector to handle this context is simple, all you need to do is to edit obj.conf and add a NameTrans line that looks like:

  NameTrans fn="assign-name" from="/<context name>/*" name="jknsapi"

After saving obj.conf restart Netscape and it will serve the new context.

Advanced Context Configuration

Sometimes it is better to have Netscape serve the static pages (html, gif, jpeg etc.) even if these files are part of a context served by Tomcat. For example, consider the html and gif files in the examples context, there is no need to serve them from the Tomcat process, Netscape will suffice.

Making Netscape serve static files that are part of the Tomcat contexts requires the following:

  • Configuring Netscape to know about the Tomcat contexts
  • Make sure that the WEB-INF directory is protected from access.
  • Configuring Netscape to assign the NSAPI redirector only specific requests that requires JSP/Servlet handling.

Adding a Tomcat context to Netscape requires the addition of a new Netscape virtual directory that covers the Tomcat context.

For example, adding a /example Netscape virtual directory that covers the c:\tomcat\webapps\examples directory.

To add a new virtual directory add the following line to your obj.conf:

  NameTrans fn=pfx2dir from=/examples dir="c:/tomcat/webapps/examples"

WEB-INF protection requires some explanation; Each servlet application (context) has a special directory named WEB-INF, this directory contains sensitive configurations data and Java classes and must be kept hidden from web users. WEB-INF can be protected by adding the following line to the PathCheck section in the default configuration object:

  PathCheck fn="deny-existence" path="*/WEB-INF/*"
  
  This line instructs the Netscape server to reject any request with a URL that contain the path /WEB-INF/.

Configuring Netscape to assign the NSAPI redirector only specific requests is somewhat harder, you will need to specify the exact URL-Path pattern(s) that you want Tomcat to handle (usually only JSP files and servlets).

This requires a change to NameTrans portion of obj.conf.

  For the examples context it requires to replace the following line:
  
  NameTrans fn="assign-name" from="/examples/*" name="jknsapi"
  
  with the following two lines:
  
  NameTrans fn="assign-name" from="/examples/jsp/*.jsp" name="jknsapi"
  NameTrans fn="assign-name" from="/examples/servlet/*" name="jknsapi"

As you can see the second configuration is more explicit, it actually instructs Netscape to assign the redirector with only requests to resources under /examples/servlet/ and resources under /examples/ whose name ends with .jsp.

You can be even more explicit and provide lines such as:

  NameTrans fn="assign-name" from="/examples/servletname" name="jknsapi"
  
  Instructs Netscape to assign the redirector request whose URL-Path equals /example/servletname
Advanced Worker Configuration

Sometimes you want to serve different contexts with different Tomcat processes (for example to spread the load among different machines). To achieve such goal you will need to define several workers and assign each context with its own worker.

Defining workers is done in workers.properties, this file includes two types of entries:

  #An entry that lists all the workers defined. For example:
  worker.list=worker1,worker2
  
  # Entries that define the host and port associated with these workers.
  worker.worker1.host=localhost
  worker.worker1.port=8009
  worker.worker1.type=ajp13

  worker.worker2.host=otherhost
  worker.worker2.port=8009
  worker.worker2.type=ajp13

The above examples defined two workers, now we can use these workers to serve two different contexts each with it's own worker. Submitting requests to different workers is accomplished by using multiple Service directives in the servlet configuration Object, each with a different path pattern parameter.

For example, if we want to submit the /examples context to the worker named worker1 and the /webpages context to the worker named worker2 we should use the following configuration:

  <Object name="jknsapi">
  ObjectType fn=force-type type=text/plain
  Service fn="jk_service" worker="worker1" path="/examples/*"
  Service fn="jk_service" worker="worker2" path="/webpages/*"
  Service fn="jk_service" worker="worker1"
  </Object>

More informations on using and configuring workers in the Workers HowTo and in the worker.properties configuration reference.

Building NSAPI DLL redirector for Windows

The redirector was developed using Visual C++ Ver.6.0, so having this environment is a prereq if you want to perform a custom build. You should also have NES developer SDK The steps that you need to take are:

  • Change directory to the nsapi plugins source directory.
  • Edit nsapi.dsp and update the include and library path to reflect your own Netscape server installation (search for a /I compiler option and /libpath linker option)
  • Make the source with MSDEV
Change directory to the nsapi plugins source directory c:\>cd c:\home\apache\jk\nsapi
Build the sources using MSDEV c:\>MSDEV nsapi.dsp /MAKE ALL

If msdev is not in your path, enter the full path to msdev.exe. This will build both release and debug versions of the redirector plugin. An alternative will be to open the nsapi workspace file (nsapi.dsw) in msdev and build it using the build menu.

Building NSAPI so plugin redirector for Unix

The redirector requires either gcc (Linux) or gcc or the Sun cc compiler (Solaris). The steps that you need to take are:

  • Change directory to the nsapi plugins source directory (src/native).
  • configure for Netscape/iPlanet/SunONE webserver.
  • Change directory to the nsapi netscape directory (./netstape).
  • Set environment variables JAVA_HOME resp. SUITSPOT_HOME to the location of your Java installation resp. Netscape server installation. Depending on the web server version, you must add the subdirectory "plugins" to SUITSPOT_HOME. The variable is correct, if the file $SUITSPOT_HOME/include/nsapi.h exists.
  • Edit Makefile.solaris resp. Makefile.linux and update the variables according to your needs. In the Solaris Makefile, you need to switch the commented lines in order to use the Sun compiler cc instead of GNU gcc.
  • Make the source with gmake.
Change directory to the nsapi plugins source directory c:\>cd /usr/local/src/tomcat-connectors-xxx-src/native
configure for Netscape/iPlanet/SunONE webserver c:\>./configure --enable-netscape
Change directory to the nsapi netscape directory c:\>cd netscape
Set JAVA_HOME (ksh example) c:\>export JAVA_HOME=/path/to/my/java
Set SUITSPOT_HOME (ksh example) c:\>export SUITSPOT_HOME=/path/to/my/netscape/server
Edit the Makefile c:\>vi Makefile.solaris
Make the source with gmake c:\>gmake -f Makefile.solaris

After the build, you will have the required nsapi_redirector.so plugin.


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