2. What is Apache Tomcat?
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Apache is the most common HTTP Web Server on the
Internet. It is the Web server used at http://web.njit.edu
The Tomcat server is a Java-based Web Application
container which is used to run Servlet and Java Server
Pages (JSP) Web applications.
Tomcat has become the reference implementation for
both the Java Servlets and Java Server Pages
specifications.
Tomcat was chosen to be the official Sun Web
Component (JSP/Servlet ) Container Reference
Implementation.
3. What is Apache Tomcat? [Contd.]
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Apache Tomcat is used to serve Java Servlets and Java
Server Pages. It's a complex piece of software and
though the documentation is very comprehensive, it
helps to have a good reference work to hand.
It is an open source Java Servlet application server used
to deploy Java applications after they are built with JSP
and Servlets. It can be used as a stand-alone product or
it can be integrated with the Apache server.
4. What is a container?
Containers are the interface between a component and
the low-level platform-specific functionality that supports
the component.
Before a Web, enterprise bean, or application client
component can be executed, it must be assembled into
a J2EE module and deployed into its container.
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5. J2EE Containers (Server)
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J2EE server :
The runtime portion of a J2EE product. A J2EE server
provides EJB and Web containers.
Enterprise JavaBeans (EJB) container :
Manages the execution of enterprise beans for J2EE
applications. Enterprise beans and their container run on the
J2EE server.
Web container :
Manages the execution of JSP page and servlet
components for J2EE applications. Web components and
their container run on the J2EE server.
6. J2EE Containers (Client)
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Application client container :
Manages the execution of application client components.
Application clients and their container run on the client.
Applet container :
Manages the execution of applets. Consists of a Web
browser and Java Plug-in running on the client together.
7. J2EE Server and Containers
Client
Browser
Web Server (Apache)
Servlet
JSP page
Tomcat
Java Web Container
Application
Client
Client
Container
Client Machine
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Database
Session
Entity
Bean
Bean
EJB Container
JBoss,
WebSphere,
WebLogic, etc
8. Working environments
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Java is already installed on PCs in the
NJIT PC labs and the Solaris and Linux
labs on the second floor of GITC. Tomcat
is also installed on the Solaris machines. It
is recommended that all work with Tomcat
be done on AFS31 through AFS35.
The installation guides on the following
slides are for your own computers.
9. Initial Setup
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The Java Software Development Kit (JDK) is aimed
at Java developers. It consists of Sun's Java
Runtime Environment bundled with programming
tools. Java Runtime Environment (JRE) is the
software required to run any application deployed on
Java platform.
Download J2SE Runtime Environment
Install the JRE according to the instructions included
with the release.
10. Installation of Apache Tomcat
Initiate the download of Tomcat from the site
http://tomcat.apache.org/
View the corresponding documentation
and setup for help in running on various
platform and requirements.
After downloading follow the instructions
to start installation.
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11. Start Up Tomcat
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Tomcat can be started by executing the following
commands:
$CATALINA_HOMEbinstartup.bat
(Windows)
$CATALINA_HOME/bin/startup.sh
(Unix)
After startup, the default web applications included with
Tomcat will be available by visiting:
http://localhost:8080/
13. Shut Down Tomcat
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Tomcat can be shut down by executing the following
command:
$CATALINA_HOMEbinshutdown
(Windows)
$CATALINA_HOME/bin/shutdown.sh (Unix)
14. Enabling SSI and CGI
support
SSI and CGI are disabled by default for
security reasons to enable them:
To enable and configure CGI support,
please see the cgi-howto.html page.
To enable and configue SSI support,
please see the ssi-howto.html page.
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15. Security Managers URL
In order to grant security permissions to JARs
located inside the web application repository,
use URLs of of the following format in your
policy file:
file:${catalina.home}/webapps/examples/WEBINF/lib/driver.jar
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16. Enabling invoker servlet:
(NJIT is non-standard)
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Starting with Tomcat 4.1.12, the invoker servlet is no longer
available by default in all webapps. Enabling it for all webapps is
possible by editing $CATALINA_HOME/conf/web.xml to uncomment
the "/servlet/*" servlet-mapping definition.
Using the invoker servlet in a production environment is not
recommended and is unsupported. More details are available on
the Tomcat FAQ at
http://tomcat.apache.org/faq/misc.html#invoker.
WARNING! On NJIT Systems, the invoker “servlet” is in use, and
needs to be maintained if you edit your web.xml. A URL must be in
the form http://web.njit.edu/~<ucid>/servlet/<classname> for the
servlet to be found and executed by Tomcat.
17. UCS at NJIT
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Apache Tomcat is installed on UCS and
servlets can be run after configuration of your
account.
Basic information will be available from link:
http://web.njit.edu/all_topics/Servers/Tomcat/
Changes to servlets are seen immediately. The
first time you set up Tomcat, servlets are visible
only after the NJIT server is restarted which is
done once a day at 6:00 AM.
As of 03/2008 Apache is running on afs31-afs35.
18. Any other web server using
port 8080
This happens usually when any other web server (or any
process) has laid claim to port 8080 and this one is the
default HTTP port that Tomcat attempts to bind to at
startup. So for changing this, open the file:
$CATALINA_HOME/conf/server.xml
and search for '8080'. Change it to a port that isn't in use,
and is greater than 1024, as ports less than or equal
1024 require superuser (root) access to bind under UNIX.
Restart Tomcat. Be sure that you replace the "8080“ in
the URL you're using to access Tomcat. If you change
the port to 1977, you would request the URL
http://localhost:1977/ in your browser.
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19. Out of environment space error
An "out of environment space" error
This happens when running the batch files in
Windows 95, 98, or ME operating systems. Right-click
on the STARTUP.BAT and SHUTDOWN.BAT files.
Click on "Properties", then on the "Memory" tab. For
the "Initial environment" field, enter in something like
4096. After you click apply, Windows will create
shortcuts which you can use to start and stop the
container.
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20. The 'localhost' machine isn't
found error
The 'localhost' machine isn't found.
This could happen if you're behind a proxy. If that's
the case, make sure the proxy configuration for your
browser knows that you shouldn't be going through
the proxy to access the "localhost". In Netscape, this
is under Edit/Preferences -> Advanced/Proxies, and
in Internet Explorer, Tools -> Internet Options ->
Connections -> LAN Settings.
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21. Apache Tomcat Updates
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The latest version of Apache Tomcat
changes regularly so keep updated by
visiting the link :
http://tomcat.apache.org/
22. Advantages of Tomcat
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1) It is an open source application server
2) It is a light weight server (no EJB)
3) It is easily configured with apache and IIS
4) Very stable on Unix systems
5) Good documentation online
6) Java Sun compliant
7) Does not require a lot of memory at startup
8) It is free, yet high quality!
