Apache Software Foundation | Jakarta Project | Apache Tomcat
Introduction
This document explains how to set up Netscape web servers to cooperate with Tomcat. Normally the Netscape web servers come with their own Servlet engine, but you can also configure them to send servlet and JSP requests to Tomcat using the Tomcat redirector plugin. It is recommanded that you also read the Workers HowTo document to learn how to setup the working entities between your WebServer 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:\jakarta-tomcat . A worker is defined to be a tomcat process that accepts work from the Netscape/iPlanet server.
Supported Configuration
The Netscape-Tomcat redirector was developed and tested on: WinNT4.0-i386 SP4/SP5/SP6a (should be able to work with other service packs) and some Unixes Netscape Enterprise 3.0 and 3.61 Tomcat 3.2.x, 3.3.x, Tomcat 4.0.x, Tomcat 4.1.x and Tomcat 5 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 4.0.x, 4.1.x and 5. 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 ?
The Netscape-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. 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. 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. 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. The extension collects the response from the worker and returns it to the browser.
Installation
A pre-built version of the Netscape redirector, nsapi_redirect.dll, may be available under the win32/i386 directory of jakarta-tomcat-connectors distribution. For those using Netscape as your browser, try downloading a zip version of the file, if available. There can be problems using Netscape to download DLL files. You can also build a copy locally from the source present in jakarta-tomcat-connectors distribution. The Tomcat redirector requires two entities: nsapi_redirect.dll - The Netscape server plugin, either obtain a pre-built DLL 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 in c:\jk\conf and you created a log directory c:\jk\logs If the Netscape built in servlet support is working disable it. Add the redirector plugin into the Netscape server configuration. Edit your server obj.conf and add the following lines:
In the Init section: `Init fn="load-modules" funcs="jk_init,jk_service" shlib="c:/jk/lib/nsapi_redirect.dll"` `Init fn="jk_init" worker_file="c:/jk/conf/workers.properties" log_level="debug" log_file="c:/jk/logs/nsapi.log"` In the default object NameTrans section `NameTrans fn="assign-name" from="/servlet/*" name="servlet"` `NameTrans fn="assign-name" from="/examples/*" name="servlet"` Create a new configuration object by adding the following lines to the end of the obj.conf file `<Object name=servlet>` `ObjectType fn=force-type type=text/plain` `Service fn="jk_service" worker="worker1"` `</Object>`
Restart Netscape (stop and start the server) That's all, now you should start tomcat and ask Netscape for http://server:port/examples/
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="servlet"`
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:\jakarta-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:/jakarta-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 NemaTrans portion of obj.conf .
For the examples context it requires to replace the following line: `NameTrans fn="assign-name" from="/examples/*" name="servlet"` with the following two lines: `NameTrans fn="assign-name" from="/examples/jsp/*.jsp" name="servlet"` `NameTrans fn="assign-name" from="/examples/servlet/*" name="servlet"`
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="servlet"` 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 its 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=servlet>` `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
Building NSAPI redirector
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.