Tomcat6 on Ubuntu

In this post I’m going to talk about getting Tomcat version 6 up and running on Ubuntu. I’m going to be using Ubuntu 10.10. Installing Tomcat is quite simple, due to it being in the repositories. Simply run:

sudo apt-get install tomcat6 tomcat6-admin tomcat6-examples tomcat6-docs

And that’s it 🙂 You now have a working install of Tomcat version 6 on your machine. In order to see it working point your browser to http://localhost:8080/. You’ll see the Apache “It Works!” message as well as a message about where everything is and links to the docs, examples, manager and host-manager applications.

Now, in order to get access to the manager and host-manager applications you’re going to have to add a user. To do this, modify the file at /etc/tomcat6/tomcat-users.xml and add the following section:

<role rolename=”admin”/>
<role rolename=”manager”/>
<user username=”srdan” password=”password” roles=”admin,manager”/>

After editing the file and restarting the Tomcat server we should be able to log into the manager application by pointing our browser at http://localhost:8080/manager/html and we should be able to log into the host-manager by going to http://localhost:8080/host-manager/html. The manager will allow us to deploy, undeploy, start and stop our applications and the host-manager allows us to declare, remove, start and stop our virtual hosts.

NOTE: From Tomcat 6.0.3 onwards, there is no “manager” role that is recognised by the manager application, rather it has been split up into four roles for security purposes:

manager-gui – allows access to the HTML GUI and the status pages
manager-script – allows access to the text interface and the status pages
manager-jmx – allows access to the JMX proxy and the status pages
manager-status – allows access to the status pages only

To test out the deployment, we’re going to create a very simple web application. First, create a new directory and change into it:

mkdir HelloWorld
cd HelloWorld

Next we’re going to create a servlet with the following code:

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HelloWorld 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>Hello World!</title>”);
out.println(“</head>”);
out.println(“<body>”);

out.println(“<h1>Hello World!</h1>);

out.println(“</body>”);
out.println(“</html>”);
}
}
And put it into a file called HelloWorld.java. After this we need to create a WEB-INF and WEB-INF/classes directory. Once we’ve done this, we compile the above code with:

javac -classpath “/usr/share/tomcat6/lib/*” HelloWorld.java

This should result in a HelloWorld.class file in the same directory. We need to move this file to the WEB-INF/classes directory:

mv HelloWorld.class WEB-INF/classes/

Now we need to add a web.xml file, which is going to tell Tomcat about our application. For our purposes we need to create a file with the following contents:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>

<web-app xmlns=”http://java.sun.com/xml/ns/javaee&#8221;
xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance&#8221;
xsi:schemaLocation=”http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd&#8221;
version=”2.5″>

<description>
Simple Hello World Servlet.
</description>
<display-name>Simple Hello World Servlet</display-name>

<servlet>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>HelloWorld</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>
</web-app>

Once that’s done, make sure that the file is in the WEB-INF directory, and we can go ahead and create our war file with:

jar -cvf hello.war .

Now we should be able to go back to the manager application at http://localhost:8080/manager/html, go to the Deploy section, select our war file, upload it and have it deploy straight away.

Assuming everything went fine, we can now go to http://localhost:8080/hello/HelloWorld and see our servlet in action, printing out the famous “Hello World!” message in HTML.

That concludes this post. Hopefully now you know how to install Tomcat on Ubuntu, manage it using the manager and host-manager applications, as well as how to create and deploy a very simple web application to the server.

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