MC365 Application Servers: Tomcat

Today We Will: Discuss what application servers are Introduce Tomcat Download and install Tomcat Break up into teams to download to install Tomcat on team machines

What is an application server? Servlets are Java’s answer to server-side programming. Servlets are a special type of Java program. –Like applets and applications. Servlets can not run on their own. –That is, you don’t just execute a servlet from a command prompt or in a browser. –Servlets are looking for special objects (request and response objects). –Because of this, servlets need to be run in a container that will provide these request and response objects. –This container is called an application server.

What is an application server? Application servers usually work in concert with a web server. –In fact, today’s app servers usually have web servers built in. Here is how the process works: –The user submits a request from a browser (e.g. Netscape, IE) –The web server receives the request from the browser and recognizes it as a special request for a servlet. This is done by configuring the web server to recognize certain url’s as servlet requests. –The web server passes the request to the application server. –The application server processes the request and returns a response to the web server. –The web server passes the response to the browser.

Tomcat There are dozens of application servers on the market. The market leaders are WebLogic, WebSphere and Tomcat – probably in that order. –WebLogic and WebSphere are usually chosen for very large enterprises. Industrial strength with many bells and whistles like clustering, transaction mgmt, EJB support, load balancing, fail-over support, etc. Also VERY expensive. –Tomcat is the server of choice for more of the small-to- medium size organizations. It is a very solid application server that has most of the functionality of the more expensive servers. It is also much more easy to manage and work with. It is the perfect tool to use for an introduction to app servers. Best of all, it is fee.

Installing Tomcat Tomcat needs Windows NT, 2000 Server, or XP. –It will not work on Windows 98. –If you are using a version of Unix, you will need to download the appropriate tar file. To install Tomcat go to: Save the tomcat exe to your hard drive and double- click to begin installation. Follow the directions on the screen.

Verifying Tomcat Installation Note: You should set the cache in your browsers to zero when testing servlets. –Forces the browser to make a new call to the server every time. To test your installation type in your browser: Go to servlet examples.

Starting and Stopping Tomcat There really is no need to start and stop the server. –Installs as an NT Service. –Tomcat has dynamic servlet loading. If you do want to start and stop Tomcat manually, you need to kill the NT process if it is running. Then to start and stop the server, go to Programs/Apache Tomcat 4.1/Start Tomcat (or Stop Tomcat).