Accessing Tomcat on Port 80: From example.com:8080 to example.com

Sep 09 2010

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	Accessing Tomcat on Port 80: From example.com:8080 to example.com

Solution By default Tomcat and JBoss run on port 8080. So your Tomcat urls look like http://example.com:8080/index.jsp.

There are a few ways ways you can access Tomcat webapps on the regular port 80 so that you do not need the port number in the URL.

* You can also set Tomcat to run on port 80. We do not recommend this method, since then Tomcat would need to run as a privileged user. Which has security implications.

* Another method you can use is iptables. iptables let you forward traffic received on one port (80) to another port (8080). This method bypasses the Apache webserver completely (even if it is running on port 80). This is the simple to setup. But you will not be able to use Apache (e.g. for webmail, using PHP apps, or apps like phpMyAdmin).

* Another option is to use Apache as a front end to all requests. And configure the Apache mod_jk2 module to forward certain URLs or virtual hosts to Tomcat. This option lets have some content served by Tomcat (e.g. a whole domain, or a certain directory on a domain) and other content (e.g. HTML, PHP pages, etc) served by Apache.

IPTables: Forwarding Incoming Port 80 requests to Port 8080

If you want to use Apache as a front end to Tomcat, skip this section.

If you want to use iptables to forward incoming requests on port 80 to Tomcat on port 8080, run these commands to setup an iptable rule:

# install the iptables applications if they are not already there
apt-get -y install iptables
# prevent Apache from running on startup
chkconfig --del httpd
# stop Apache from running right now
/etc/rc.d/init.d/httpd stop
# tell iptables to forward incoming requests on port 80 to tomcat
/sbin/iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
# save the iptable rules
/sbin/iptables-save
# make sure iptables starts up by default after a server restart
chkconfig --level 35 iptables on

You may get a QM_MODULES warning. You can safely ignore that. Our VPS servers are built without modules and with the iptable features built into kernel itself. The iptables scripts just do not detect that modules are not available and do not know to skip that step.

If you decide to turn off your iptables rules, run this:

iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -F
/sbin/iptables-save
# make sure iptables starts up by default after a server restart
chkconfig --level 35 iptables off

Running JSP Through Apache: mod_jk2

Often customers want to combine the use of JSP and Apache. For example, they may have some PHP scripts and some JSP programs they want to run. (And the Servlet engines cannot execute PHP scripts). Using Apache to handle your incoming requests also gives you more options for things like using SSL, error logs, and using .htaccess files.

The answer is to use the Apache mod_jk2 module. It intercepts Apache requests to certain URLs and forwards them to your Servlet engine. For example, it can hand off requests to certain "mount points" like /jsp to your Servlet engine. It can also hand off certain file types (e.g. *.jsp) to your Servlet engine.

mod_jk2 forwards the Apache requests to your Servlet engine via a socket using a protocol called ajp13. Both Tomcat and Jetty support the ajp13 protocol.

First Step: Serve Content on Default Servlet Port

The first step towards running your webapps with Apache as a front end, is to first get them working directly from your default servlet eninge port. 8080 is the default port for Tomcat (including JBoss/Tomcat) and Jetty. Taking this step before testing the mod_jk2 setup makes troubleshooting problems easier:

1. Set up your web apps (you may use any of the installed Servlet engines, they all support mod_jk2).
2. Make sure your can browse your webapp using a URL like: http://yourip:8080/jsp/index.jsp. When using Apache as a front end, it is best to not use a 'ROOT' mounted webapp.
3. Do not run the iptables command to forward port 80 requests to the Servlet engine (since we want Apache to handle the incoming requests).
4. Test you can load your web app on http://yourip/jsp/index.jsp

Note: your Servlet container needs to listen for connections from Apache.

Next Steps: Serving up your WebApp from Apache

We can isntall the mod_jk2.so module binary for the Fedora, White Box Enterprise Linux 3 and recent Red Hat 9 distributions per request.

mod_jk2 is configured in the /etc/httpd/conf.d/mod_jk2.conf file.

This file includes a sample 'Location'. It looks like this:

JkUriSet worker ajp13:localhost:8009

This Location tag will direct requests to http://yourdomain/jsp-examples to the jsp-examples webapp (if one exists) on your Servlet engine.

If you want to run your own webapp instead, just edit this file and rename jsp-examples to your own webapp's name. Alternatively you can add your own Location tags in /etc/httpd/conf/httpd.conf.

You can put the Location tag inside a VirtualHost tag if you want the Location to only work for a particular domain. Note: on some servers there seems to be a problem where the VirtualHost is ignored, and the Location is used across all domains. In this case you will need to setup a workers2.properties.

ROOT WebApps

If you want to have all requests go to Tomcat, use a Location of / and your requests will go to the Tomcat ROOT webapp.

If you want to mix and match Apache and Servlet engine requests for the domain, you may need to change the Location tag. For example, set it to /*.jsp and /*.do. This will make it so only the Servlet related requests go to the Servlet engine.

Tomcat Host Directive: When Each Domain Has Their Own Root Webapp

Do you have more than one domain and you want each domain to use a different root webapp? Then you will need to use Tomcat Host directives so that Tomcat knows which webapp to serve for which domain.

Setup Apache VirtualHosts. Then add a Location tag inside each of the VirtualHost directives in /etc/httpd/conf/httpd.conf, e.g.

ServerName yourdomain.com
ServerAlias *.yourdomain.com

JkUriSet worker ajp13:localhost:8009

In your server.xml file (usually /usr/local/tomcat/conf/server.xml) add something like:

appBase="/usr/local/tomcat/webapps">

www.your2nddomain.com

These directives setup the default webapps for each of the virtual hosts.

Then restart Apache and Tomcat.

Note: The server.xml changes are only required if you want to run multiple virtual hosts with different ROOT webapps. If you just have multiple virtual hosts with uniquely named webapps, they are not required. Just use the regular Location tags and make sure the webapp name and the Location directory match.

workers2.properties: When Location Tags Inside VirtualHost Directives Do Not Work

On some versions of mod_jk2 and Apache we have noticed a problem where Apache ignores the VirtualHost that a Location tag is nested within. For example, a Location / inside one VirtualHost ends up applying to all VirtualHosts on the server. So that all requests go to Tomcat, not just the requests for the intended domain.

To workaround this problem, remove your Location directives. Create a /etc/httpd/conf/workers2.properties file. Then add directives like:

[uri:yourdomain.com:80/*]
worker=ajp13:localhost:8009
[uri:your2nddomain.com:80/*]
worker=ajp13:localhost:8009

These directives will pass the requests to the named virtual hosts to your Java server. If you have yourdomain.com and www.yourdomain.com you'll need to add both those [uri] directives for each.

Article Details

Article ID:

138

Created On:

May 05 2006 11:30 PM