his article is a step by step guide for installing Apache Tomcat 6.0 (6.0.18) on 64-bit Debian Linux 4.0.
It covers the setup of multiple Tomcat JVM instances on a single Linux server.
The instructions in this guide are applicable to most other Linux distributions.
Contents
* Introduction
* Installing Java Runtime Environment
* Installing Tomcat Software
Starting/Stopping Tomcat
Switching to Tomcat User Account
* Setting Up First Tomcat JVM Instance
Setting up Directories and Files
Configuring Tomcat Network Ports
Starting First Tomcat Instance
Relaying HTTP Port 80 Connections to Tomcat Port 8080
Connecting to First Tomcat Instance Using Default HTTP Port
* Setting Up a Web Application for First Tomcat JVM Instance
Setting up Web Application Layout
Configuring Web Application
Home Page for Web Application
Restarting First Tomcat Instance
* Deploying Java Servlet for Web Application in First Tomcat JVM Instance
Setting up Java Servlet Layout
JAR Files
Creating a Java Servlet
Configuring the Java Servlet
Testing and Executing the Java Servlet
* Setting Up Second Tomcat JVM Instance
General
Steps for Second Tomcat JVM Instance and Application
* Bibliography and References
This article discusses how to install Apache Tomcat 6.0 (6.0.18) on 64-bit Debian Linux 4.0.
Additionally it shows how to setup multiple Tomcat JVM instances on a single Linux server.
For each Tomcat JVM instance a web application and Java servlet example is configured.
The Tomcat installation steps outlined in this article are also applicable to most other Linux distributions.
Note that this document comes without warranty of any kind. But every
effort has been made to provide the information as accurate as
possible.
I welcome emails from any readers with comments, suggestions, and
corrections at webmaster_at_puschitz.com.
To run Tomcat, you need Java Standard Edition (Java SE), also known as the JDK.
For the Tomcat installation I used SUN's latest Java SE JDK that was available at the time of this writing:
Java SE Development Kit (JDK) 6 Update 10 (6u10).
Regarding Java SE 6, Platform Name and Version Numbers, see
http://java.sun.com/javase/6/webnotes/version-6.html.
And for the whole Java version history I recommend the Wiki article
http://en.wikipedia.org/wiki/Java_version_history.
You can download SUN's latest Java JDKs at:
http://java.sun.com/javase/downloads/index.jsp.
For my 64-bit Debian system I selected the 64-bit JDK multiplatform binary for Linux:
jdk-6u10-linux-x64.bin.
I downloaded the binary file to
/tmp and installed it as follows as root:
# mkdir -p /usr/java
# cd /usr/java
#
# chmod 700 /tmp/jdk-6u10-linux-x64.bin
# /tmp/jdk-6u10-linux-x64.bin
...
creating: jdk1.6.0_10/
creating: jdk1.6.0_10/db/
creating: jdk1.6.0_10/db/bin/
inflating: jdk1.6.0_10/db/bin/ij
inflating: jdk1.6.0_10/db/bin/NetworkServerControl
inflating: jdk1.6.0_10/db/bin/setNetworkClientCP.bat
inflating: jdk1.6.0_10/db/bin/derby_common.sh
...
Done.
# export JAVA_HOME=/usr/java/jdk1.6.0_10
# export PATH=$JAVA_HOME/bin:$PATH
#
# which java
/usr/java/jdk1.6.0_10/bin/java
# java -version
java version "1.6.0_10"
Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
Java HotSpot(TM) 64-Bit Server VM (build 11.0-b15, mixed mode)
#
Download the latest Tomcat 6.x version from
http://tomcat.apache.org/download-60.cgi.
For Debian I downloaded the Binary Core Distribution file
apache-tomcat-6.0.18.tar.gz which was the
latest version at the time of this writing.
Once you downloaded the tar file make sure the
MD5 checksum matches the value posted on Tomcat's web site, see
http://www.apache.org/dist/tomcat/tomcat-6/v6.0.18/bin/apache-tomcat-6.0.18.tar.gz.md5:
# md5sum /tmp/apache-tomcat-6.0.18.tar.gz
8354e156f097158f8d7b699078fd39c1 /tmp/apache-tomcat-6.0.18.tar.gz
Installing Tomcat from a binary release (tar file) requires manual creation of the Tomcat user account.
This is not necessary if you install the Tomcat RPM package on a Linux system that supports RPMs.
For security reasons I created a user account with no login shell for running the Tomcat server:
# groupadd tomcat
# useradd -g tomcat -s /usr/sbin/nologin -m -d /home/tomcat tomcat
(It should be noted that other Linux systems have
nologin under
/sbin not
/usr/sbin)
Next I extracted the tar file to
/var/lib and changed the ownership of all files and directories to
tomcat:
# cd /var/lib
# tar zxvf /tmp/apache-tomcat-6.0.18.tar.gz
# chown -R tomcat.tomcat /var/lib/apache-tomcat-6.0.18
The get the Tomcat version of the newly installed Tomcat, run:
# /var/lib/apache-tomcat-6.0.18/bin/version.sh
Using CATALINA_BASE: /var/lib/apache-tomcat-6.0.18
Using CATALINA_HOME: /var/lib/apache-tomcat-6.0.18
Using CATALINA_TMPDIR: /var/lib/apache-tomcat-6.0.18/temp
Using JRE_HOME: /usr
Server version: Apache Tomcat/6.0.18
Server built: Jul 22 2008 02:00:36
Server number: 6.0.18.0
OS Name: Linux
OS Version: 2.6.18-6-amd64
Architecture: x86_64
JVM Version: 1.4.2
JVM Vendor: Free Software Foundation, Inc.
#
Starting/Stopping Tomcat
Now try to startup the Tomcat server to see whether the default Tomcat home page is being displayed.
For security reasons I don't run the Tomcat server as user
root but as
tomcat which was created with no login shell.
Therefore, to run Tomcat use the
su command with the
-p option to preserves
all the environment variables when switching to
tomcat (more on the Tomcat environment variables later).
And since the
tomcat account has no login shell, it needs to be specified with the
-s option.
(You may want to use this
su command if you plan on writing and implementing a system startup and shutdown script for system reboots.)
# export JAVA_HOME=/usr/java/jdk1.6.0_10
# export PATH=$JAVA_HOME/bin:$PATH
# export CATALINA_HOME=/var/lib/apache-tomcat-6.0.18
# export CATALINA_BASE=/var/lib/apache-tomcat-6.0.18
#
# su -p -s /bin/sh tomcat $CATALINA_HOME/bin/startup.sh
Using CATALINA_BASE: /var/lib/apache-tomcat-6.0.18
Using CATALINA_HOME: /var/lib/apache-tomcat-6.0.18
Using CATALINA_TMPDIR: /var/lib/apache-tomcat-6.0.18/temp
Using JRE_HOME: /usr/java/jdk1.6.0_10
#
Now verify that Tomcat was started successfully by opening the URL
http://localhost:8080 (Port number 8080 is the default port used by Tomcat).
Note that you should also be able to use the name of your server instead of
localhost.
Once you opened the URL in your browser you should see Tomcat's Congratulation page.
If you don't see the page, check the log files under
$CATALINA_HOME/logs (
/var/lib/apache-tomcat-6.0.18/logs).
Before you continue with the next steps, make sure to shut down Tomcat since we want to run the Tomcat server out of a separate
application directory which is covered in the next chapter.
# su -p -s /bin/sh tomcat $CATALINA_HOME/bin/shutdown.sh
Using CATALINA_BASE: /var/lib/apache-tomcat-6.0.18
Using CATALINA_HOME: /var/lib/apache-tomcat-6.0.18
Using CATALINA_TMPDIR: /var/lib/apache-tomcat-6.0.18/temp
Using JRE_HOME: /usr/java/jdk1.6.0_10
#
Switching to Tomcat User Account
Most of the next steps in this article assume that you switched to the
tomcat user account.
If you see a '
$' prompt, then the steps in this article are executed as the
tomcat user.
If you see a '
#' prompt, then the steps are executed as
root.
Since for security reasons the
tomcat user has no login shell, it needs to be specified with the
-s option when switching from
root to
tomcat:
# su - -s /bin/sh tomcat
$ id
uid=1001(tomcat) gid=1001(tomcat) groups=1001(tomcat)
$
Note that non-root users cannot switch to the
tomcat account.
It is recommended not to store the web applications's files in Tomcat's distribution directory tree.
For example, having a separate directory makes Tomcat upgrades easier since it won't
overwrite configuration files like
server.xml. And since this tutorial shows how to run two
Tomcat instances concurrently on a single Linux server, two separate directories are needed anyway.
It should be noted here that it's also possible to run multiple web applications per Tomcat JVM instance.
This HOWTO shows the creation and configuration of one web application for each Tomcat instance.
Setting up Directories and Files
In the following example I setup the first Tomcat JVM instance under the base directory
/opt/tomcat-instance/sales.example.com.
It's a good practice to name the base directory after the site name, in this example
sales.example.com.
Creating a new base directory for a new instance requires the creation and copying of various directories and
configuration files. Execute the following commands as
root:
# mkdir -p /opt/tomcat-instance/sales.example.com
# cd /opt/tomcat-instance/sales.example.com
#
# cp -a /var/lib/apache-tomcat-6.0.18/conf .
# mkdir common logs temp server shared webapps work
#
# chown -R tomcat.tomcat /opt/tomcat-instance
Most of the remaining steps are executed as the
tomcat user. So make sure you switch from
root
to
tomcat:
# su - -s /bin/sh tomcat
$ id
uid=1001(tomcat) gid=1001(tomcat) groups=1001(tomcat)
$
Next I created an environment file for the new Tomcat instance.
This will be useful for easily setting the environment variables when starting/stopping the new Tomcat instance:
$ cat > /opt/tomcat-instance/sales.env << EOF
export JAVA_HOME=/usr/java/jdk1.6.0_10
export PATH=\$JAVA_HOME/bin:\$PATH
export CATALINA_HOME=/var/lib/apache-tomcat-6.0.18
export CATALINA_BASE=/opt/tomcat-instance/sales.example.com
EOF
$
$ cat /opt/tomcat-instance/sales.env
export JAVA_HOME=/usr/java/jdk1.6.0_10
export PATH=$JAVA_HOME/bin:$PATH
export CATALINA_HOME=/var/lib/apache-tomcat-6.0.18
export CATALINA_BASE=/opt/tomcat-instance/sales.example.com
$
CATALINA_HOME is the base directory of Tomcat that contains all the libraries, scripts etc. for Tomcat.
This is the parent directory of the extracted Tomcat tar file.
CATALINA_BASE is the base directory of the new Tomcat instance, which in this example points to
/opt/tomcat-instance/sales.example.com.
Configuring Tomcat Network Ports
Since this is the first Tomcat instance that's being created here, the default port numbers can be left unchanged
in
$CATALINA_BASE/conf/server.xml (
/opt/tomcat-instance/sales.example.com/conf/server.xml):
<Server port="8005" shutdown="SHUTDOWN">
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
However, these port numbers will have to be changed for the second Tomcat instance though, see
Steps for Second Tomcat JVM Instance and Application.
Starting First Tomcat Instance
To start the newly created Tomcat JVM instance, ensure that the
environment variables are set for the new instance and execute the
startup script:
$ source /opt/tomcat-instance/sales.env
$ $CATALINA_HOME/bin/startup.sh
Using CATALINA_BASE: /opt/tomcat-instance/sales.example.com
Using CATALINA_HOME: /var/lib/apache-tomcat-6.0.18
Using CATALINA_TMPDIR: /opt/tomcat-instance/sales.example.com/temp
Using JRE_HOME: /usr/java/jdk1.6.0_10
$
If everything has been configured correctly, you should now see an empty white page when opening the URL
http://localhost:8080.
Note that instead of
localhost you should also be able to use the name of your server.
If you get an error in the browser instead of an empty page, check the log files under
$CATALINA_BASE/logs (
/opt/tomcat-instance/sales.example.com/logs).
Note that since
CATALINA_BASE has been changed for the new Tomcat instance, the logs are no longer written to
/var/lib/apache-tomcat-6.0.18/logs.
Relaying HTTP Port 80 Connections to Tomcat Port 8080
By default, Tomcat listens on port 8080. To have the Tomcat server itself listen on HTTP port 80, Tomcat would have to run as
root
since only
root can listen on ports below 1024 on Linux. But for security reasons this is not recommended.
The solution I prefer is to relay port 80 TCP connections to port 8080 using the
Netfilter package
that comes with Linux.
An alternate solution would be to use a service wrapper like
jsvc from the
Jakarta Commons Daemon project. But this solution would require the installation and maintenance of another
piece of software on my system that I want to avoid.
The Netfilter package that comes already with Linux is transparent to
Tomcat. The following steps show how to relay port 80 TCP connections to
Tomcat's
port 8080 using the
iptables command from the Netfilter package. Note that these steps must be executed as
root:
# iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8080
# iptables -t nat -I OUTPUT -p tcp --dport 80 -j REDIRECT --to-ports 8080
The first rule redirects incoming requests on port 80 generated from other computer nodes, and the second rule
redirects incoming requests on port 80 generated from the local node where Tomcat is running.
To see the newly configured rules, run:
# iptables -t nat -L
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
REDIRECT tcp -- anywhere anywhere tcp dpt:www redir ports 8080
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
REDIRECT tcp -- anywhere anywhere tcp dpt:www redir ports 8080
#
To remove the NAT rules we just created, you can run the
iptables -t nat -F command which flushes and deletes the rules.
Note that this will also flush any other rules that may have been configured on your system!
For more information on
iptables, see
netfilter/iptables documentation.
To make the rules permanent for reboots, you can use the following option outlined here for Debian
(other Linux distributions have other methods). First save the newly created rules in a file:
# iptables-save > /etc/iptables.conf
Then edit the
/etc/network/interfaces file and add the line highlighted in blue for the public network interface. For example:
iface eth0 inet static
address 192.168.1.23
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1
pre-up iptables-restore < /etc/iptables.conf
The
pre-up configuration in this example activates the
iptables rules on my system before the public interface
eth0 comes up.
So the rules can be seen with
iptables -t nat -L after each reboot.
Note that for security reasons it's important that firewall rules are established before the network interfaces come up.
Even though this is not an issue for relaying Tomcat connections, as a matter of good practice, the
iptables rules should always
be established before the network comes up.
It should be noted here that there is one Tomcat configuration parameter that you may or may not want to change, the
proxyPort
parameter in the
server.xml file.
Since Tomcat still receives requests on port 8080 as they are relayed by the Linux Netfilter system from port 80,
Tomcat may display port 8080 in the URL depending on the application's content.
So if you want to change it to port 80, the
proxyPort parameter would need to be added in the
$CATALINA_BASE/conf/server.xml (
/opt/tomcat-instance/sales.example.com/conf/server.xml).
file for port 8080:
<Connector port="8080" protocol="HTTP/1.1" proxyPort="80"
connectionTimeout="20000"
redirectPort="8443" />
After that you need to restart Tomcat to make this change effective.
Connecting to First Tomcat Instance Using Default HTTP Port
If
iptables have been configured correctly, you should now be able to open the URL
http://localhost and see an
empty white page.
You could also use the URL
http://localhost:80 (port 80 is the default port used by browsers) or the name of your server.
If you get an error in the browser instead of an empty page, check the
iptables configuration and check the log files under
$CATALINA_BASE/logs (
/opt/tomcat-instance/sales.example.com/logs).
Note that since
CATALINA_BASE was changed for the new Tomcat instance, the logs are no longer written to
/var/lib/apache-tomcat-6.0.18/logs.
You can setup multiple web applications for each Tomcat JVM instance. In this guide we are setting up one web application for
each Tomcat JVM instance.
First make sure to switch to the
tomcat user account and source in the environment variables for the remaining steps:
# su - -s /bin/sh tomcat
$ source /opt/tomcat-instance/sales.env
Setting up Web Application Layout
In the previous chapter the first Tomcat JVM instance was setup under the base directory
$CATALINA_BASE (
/opt/tomcat-instance/sales.example.com).
In the following example I create a new directory called "
sales" under
$CATALINA_BASE/webapps which
will become the root directory for the first web application, that is
$CATALINA_BASE/webapps/sales. In Tomcat web application root directories
are created under
$CATALINA_BASE/webapps by default.
$ mkdir $CATALINA_BASE/webapps/sales
Configuring Web Application
To configure Tomcat to recognize the new web application under
$CATALINA_BASE/webapps/sales (
/opt/tomcat-instance/sales.example.com/webapps/sales),
the
$CATALINA_BASE/conf/server.xml file needs to be edited.
This is done by adding a new
Context element with the
path and
docBase attributes.
Note that Tomcat refers to webapps as "context". So
Context here represents the configuration of a web application.
The
path attribute is the application name used within the URL, and the
docBase attribute is the absolute path name
of the new web application root under
$CATALINA_BASE/webapps:
<Host name="localhost" appBase="webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Context docBase="sales" path="/mysales"/>
In this example you can see that
appBase already points to
webapps by default, that is
$CATALINA_BASE/webapps.
The newly added
path attribute points to
the
sales directory under
$CATALINA_BASE/webapps which is the location for the new application.
And the
docBase attribute is set to
mysales
which stands for the application name within the URL, i.e. "
http://localhost/mysales" or "
http://localhost:8080/mysales".
Make sure to add this new
Context element inside the
Host container element for '
localhost' which is the default host name.
Home Page for Web Application
To have a starting page for the new web application, you can simply create and add a
index.html file under the web application's root directory
$CATALINA_BASE/webapps/sales (
/opt/tomcat-instance/sales.example.com/webapps/sales).
You could also create your own JSP page here.
For testing purposes here is a simple
index.html example for the new application:
$ cat > $CATALINA_BASE/webapps/sales/index.html << EOF
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD><META http-equiv=Content-Type content="text/html"></HEAD>
<BODY>
<H3>Apache Tomcat Sales Home Page</H3>
</BODY>
</HTML>
EOF
$
Restarting First Tomcat Instance
Now check whether the new web application has been configured correctly.
To do that, run the following commands to restart the new Tomcat JVM instance:
$ source /opt/tomcat-instance/sales.env
$ $CATALINA_HOME/bin/shutdown.sh
$ $CATALINA_HOME/bin/startup.sh
If everything was configured correctly, you should now see the default home page for the new web application when
opening the URL
http://localhost/mysales or
http://localhost/mysales:8080.
Instead of
localhost you should also be able to use the name of your server.
If you get the error '
java.net.ConnectException: Connection refused' when you shutdown Tomcat, then Tomcat
was probably not running.
If you don't see the home page, check the log files under
$CATALINA_BASE/logs.
Setting up Java Servlet Layout
To follow the Java Servlet Specification for the new "sales" web application, I created the
class directory for the Java class files
under the new directory
$CATALINA_BASE/webapps/sales/WEB-INF, see also
Packaging Web Components.
The
WEB-INF directory is protected from access by browsers, meaning they are unbrowsable and safe from client views.
The
classes directory under
WEB-INF is where web components and server-side utility classes should go.
To create the
WEB-INF and
classes directories, run the following command:
$ mkdir -p $CATALINA_BASE/webapps/sales/WEB-INF/classes
JAR Files
Most Java servlets also need JAR (Java ARchive) files which should be put under the
lib directory.
Since it's a good practice to keep the application separate from the Tomcat distribution directory tree, I created
a new
lib directory under
$CATALINA_BASE/webapps/sales/WEB-INF which is consistent with
WAR's hierarchical directory structure.
$ mkdir $CATALINA_BASE/webapps/sales/WEB-INF/lib
The Java servlet example below requires the
servlet-api.jar JAR file. This JAR is already available in the Tomcat distribution directory tree
$CATALINA_HOME/lib.
You could copy this JAR file to the application's new lib directory
$CATALINA_BASE/webapps/sales/WEB-INF/lib, but then you would get the following
warning in the
$CATALINA_BASE/logs/catalina.out log file when you startup Tomcat:
INFO:
validateJarFile(/opt/tomcat-instance/sales.example.com/webapps/sales/WEB-INF/lib/servlet-api.jar)
- jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class:
javax/servlet/Servlet.class
Tomcat shows this warning since it tries now to load the JAR file twice, first from
$CATALINA_HOME/lib and then from
$CATALINA_BASE/webapps/sales/WEB-INF/lib.
Even though it's not going to be a problem for Tomcat, it's better not to keep JARs in two places. Since the
servlet-api.jar JAR file already exists
in the Tomcat distribution directory, I did not copy it to the
$CATALINA_BASE/webapps/sales/WEB-INF/lib directory.
I use this directory for application specific JARs that don't come with the Tomcat distribution.
You could also remove the JAR in
$CATALINA_HOME/lib but remember that it will reappier the next time you upgrade the Tomcat software.
Creating a Java Servlet
Since server-side classes are supposed to go to the
WEB-INF/classes directory, I created the following class file example under
$CATALINA_BASE/webapps/sales/WEB-INF/classes (
/opt/tomcat-instance/sales.example.com/webapps/sales/WEB-INF/classes) and saved it
as
Sales.java:
$ cat $CATALINA_BASE/webapps/sales/WEB-INF/classes/Sales.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Sales extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>Sales Page</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Executing Sales ...</h1>");
out.println("</body>");
out.println("</html>");
}
}
To compile the new Java servlet, the
servlet-api.jar JAR file is needed which can be specified with either
the
-classpath option or the
CLASSPATH environment variable. The
-classpath option for SDK tools is preferred
over the
CLASSPATH environment variable since it can be set individually for each application without affecting others.
In the following example I specify the path of the
class directory with the basename '
*'
(if you are unfamiliar with basename, see '
man basename').
This is equivalent to specifying all files with the extensions .jar or
.JAR files in the directory and therefore individual JAR files like
servlet-api.jar don't need to be specified.
The following command should now compile the Java servlet without errors:
$ cd $CATALINA_BASE/webapps/sales/WEB-INF/classes
$ javac -classpath "$CATALINA_HOME/lib/*" Sales.java
$ ls
Sales.class Sales.java
$
Configuring the Java Servlet
To configure servlets and other components for an application, an XML file called
web.xml needs to be configured.
The format of this file is defined in the Java Servlet Specification. In Tomcat, this file exists in two place:
$CATALINA_BASE/conf/web.xml
$CATALINA_BASE/webapps/{your-appname}/WEB-INF/web.xml
The first one is the default
web.xml file which is the base for all web applications in a Tomcat JVM instance,
and the latter one is for the web application where
WEB-INF resides for overwriting application specific settings.
For the newly created Java servlet "Sales" I created a new
web.xml file under
$CATALINA_BASE/webapps/sales/WEB-INF:
$ cat $CATALINA_BASE/webapps/sales/WEB-INF/web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<servlet>
<servlet-name>servlet_sales</servlet-name>
<servlet-class>Sales</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servlet_sales</servlet-name>
<url-pattern>/execute</url-pattern>
</servlet-mapping>
</web-app>
For each servlet there is a
<servlet> element.
It identifies the servlet name (
<servlet-name>) and the Java class name
(<servlet-class>).
The servlet mapping (
<servlet-mapping>) maps a URI to the servlet name (
<servlet-name>).
In the above example "
/execute" in "
http://localhost:8080/mysales/execute" maps to "
servlet_sales" which points to the "
Sales" servlet class.
Note that the order of these elements is important.
So when you open the URL "
http://localhost:8080/mysales/execute", the "
Sales" Java servlet will be executed.
In the following example I updated the
$CATALINA_BASE/webapps/sales/index.html file to provide an
entry point to the new Java servlet:
$ cat $CATALINA_BASE/webapps/sales/index.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD><META http-equiv=Content-Type content="text/html"></HEAD>
<BODY>
<H3>Apache Tomcat Sales Home Page</H3>
<a href="/mysales/execute">Execute Sales</a>
</BODY>
</HTML>
$
Testing and Executing the Java Servlet
Note that if you run
javac with the
-classpath option or the
CLASSPATH environment variable in the same shell before you startup Tomcat,
you will get
java.lang.NoClassDefFoundError /
java.lang.ClassNotFoundException
errors in your browser when you execute a servlet. To avoid this, simply re-login as the
tomcat user before you startup Tomcat:
# su - -s /bin/sh tomcat
$ source /opt/tomcat-instance/sales.env
$ $CATALINA_HOME/bin/shutdown.sh
$ $CATALINA_HOME/bin/startup.sh
After Tomcat restarted, open the URL
http://localhost/mysales (or use the server name instead of
localhost) and you should see the "Execute Sales" link.
Clicking on this link should invoke the Java servlet and display "Executing Sales" in your browser.
If you are presented with an empty page instead, review the above steps and make sure you didn't miss a step.
Check also the log files under
$CATALINA_BASE/logs.
General
If you've gone through all the previous steps in this HOWTO, then the
following steps should be very easy to follow and to understand
without much explanations. Therefore, I'll provide here just the steps
for setting up a second Tomcat JVM instance and
an application called "Order".
Steps for Second Tomcat JVM Instance and Application
Login as root and execute the following steps to setup the second Tomcat JVM instance:
# mkdir -p /opt/tomcat-instance/order.example.com
# cd /opt/tomcat-instance/order.example.com
#
# cp -a /var/lib/apache-tomcat-6.0.18/conf .
# mkdir common logs temp server shared webapps work
#
# chown -R tomcat.tomcat /opt/tomcat-instance/order.example.com
#
# su - -s /bin/sh tomcat
$ cat > /opt/tomcat-instance/order.env << EOF
export JAVA_HOME=/usr/java/jdk1.6.0_10
export PATH=\$JAVA_HOME/bin:\$PATH
export CATALINA_HOME=/var/lib/apache-tomcat-6.0.18
export CATALINA_BASE=/opt/tomcat-instance/order.example.com
EOF
$
$ source /opt/tomcat-instance/order.env
$
For the second Tomcat JVM instance the default port numbers need to be changed in
$CATALINA_BASE/conf/server.xml
(
/opt/tomcat-instance/order.example.com/conf/server.xml).
In the following example I increased the port numbers by one:
<Server port="8006" shutdown="SHUTDOWN">
<Connector port="8081" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8444" />
<Connector port="8010" protocol="AJP/1.3" redirectPort="8444" />
Create a new application root directory:
$ mkdir $CATALINA_BASE/webapps/order
To configure the new web application, edit
$CATALINA_BASE/conf/server.xml
(
/opt/tomcat-instance/order.example.com/conf/server.xml) and add the following entry in blue:
<Host name="localhost" appBase="webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Context docBase="order" path="/myorder"/>
Create a new home page for the new "Order" application and include a link to the Java servlet that will be setup next:
$ cat > $CATALINA_BASE/webapps/order/index.html << EOF
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD><META http-equiv=Content-Type content="text/html"></HEAD>
<BODY>
<H3>Apache Tomcat Order Home Page</H3>
<a href="/myorder/execute">Execute Order</a>
</BODY>
</HTML>
EOF
$
Now setup and create a new Java servlet:
$ mkdir -p $CATALINA_BASE/webapps/order/WEB-INF/classes
$ mkdir $CATALINA_BASE/webapps/order/WEB-INF/lib
$ cat $CATALINA_BASE/webapps/order/WEB-INF/classes/Order.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Order extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>Order Page</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Executing Order ...</h1>");
out.println("</body>");
out.println("</html>");
}
}
Compile the new Java servlet:
$ cd $CATALINA_BASE/webapps/order/WEB-INF/classes
$ javac -classpath "$CATALINA_HOME/lib/*" Order.java
$ ls
Order.class Order.java
$
Configure the Java servlet:
$ cat $CATALINA_BASE/webapps/order/WEB-INF/web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<servlet>
<servlet-name>servlet_order</servlet-name>
<servlet-class>Order</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servlet_order</servlet-name>
<url-pattern>/execute</url-pattern>
</servlet-mapping>
</web-app>
Now make sure to relogin as
tomcat and start the second Tomcat JVM instance:
# su - -s /bin/sh tomcat
$ source /opt/tomcat-instance/order.env
$ $CATALINA_HOME/bin/startup.sh
After the second Tomcat JVM restarted, open the URL
http://localhost:8081/myorder
(or use the server name instead of
localhost) and you should see the "Execute Order" link.
Clicking on this link should invoke the Java servlet and display "Executing Order" in your browser.
If you are presented with an empty page instead, review the above steps and make sure you didn't miss a step.
Check also the log files under
$CATALINA_BASE/logs.
Apache Tomcat
Tomcat: The Definitive Guide, 2nd Edition
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