Tomcat Direct Programming

Programming a Web Application - The Direct Approach

It is possible to create a Web application without using any external tool, except for a text editor (e.g. Emacs) and a Java compiler (e.g. javac).

To create a Web application, follow these instructions:

After setting up a base directory for Tomcat, create a Web-application directory under $CATALINA_BASE/webapps/. For example, $CATALINA_BASE/webapps/myApp/.
Put Web pages anywhere under the application's base directory, except for the directory WEB-INF. The relative URL of a WEB page is exactly its (Unix-style) path relative to $CATALINA_BASE/webapps/. For example, the file $CATALINA_BASE/webapps/myApp/a.html is accessible by the URL http://localhost:8090/myApp/a.html, assuming that Tomcat runs on localhost on port 8090. As another example, the file $CATALINA_BASE/webapps/myApp/a/b/c.jsp is accessible by the URL http://localhost:8090/myApp/a/b/c.jsp.
Put your Java source files under the directory WEB-INF/src/.
Put your compiled Java classes under the directory WEB-INF/classes/.
Put JAR files that contain Java classes under the directory WEB-INF/lib/.
If you are using Servlets, write down the Servlets declaration and mapping (as thought in class) in WEB-INF/web.xml.

To access your application, you will have to restart Tomcat. You will also have to restart Tomcat to reflect changes you make in your Java class files and in the file WEB-INF/web.xml.

An Example

In the following example, we create a Web application named dbinfo. This application shows a user a list of her tables in her Oracle database (used by our course). For this application, we use a Web page and a Servlet (click to view ShowTables.java, tables.html and web.xml).

The following image shows the commands executed from the Unix shell in our school. We use Emacs to edit our files.

After (re)starting Tomcat, the application is accessible using Mozilla:

Notes

Classes under WEB-INF/classes/ should follow the classpath rules when using packages. For example, if the class MyClass is located in the package myPackage then the file MyClass.class should be placed under WEB-INF/classes/myPackage/. It is conventional to follow these rules for your Java source files, under the directory src.
Note that the suitable Oracle driver is accessible from the Servlet. This is due to the fact that the directory $CATALINA_BASE/shared/lib/ is a soft link to ~dbi/tomcat/shared/lib/ and the latter directory contains the suitable JAR file.