Servlets are Java classes which service HTTP demands and implement the javax.servlet.Servlet interface. Web application developers classically write servlets that extend javax.servlet.http.HttpServlet, an abstract class that implements the Servlet interface and is specially designed to handle HTTP requests.
Resulting is the example source code structure of a servlet example to show Hello World –
Let us build a file with name HelloWorld.java with the code revealed above. Place this file at C:\ServletDevel (in Windows) or at /usr/ServletDevel (in Unix). This path location must be added to CLASSPATH before proceeding further.
Assuming your environment is setup correctly, go in ServletDevel directory and compile HelloWorld.java as follows –
If the servlet be contingent on any other libraries, you have to comprise those JAR files on your CLASSPATH as well. I have comprised only servlet-api.jar JAR file because I'm not using any other library in Hello World program.
This command line uses the built-in javac compiler that comes with the Sun Microsystems Java Software Development Kit (JDK). For this command to work correctly, you have to comprise the location of the Java SDK that you are using in the PATH environment variable.
If all goes fine, above compilation would produce HelloWorld.classfile in the same directory. Next section would explain how a compiled servlet would be deployed in production.
By default, a servlet application is located at the path <Tomcat-installationdirectory>/webapps/ROOT and the class file would reside in <Tomcat-installationdirectory>/webapps/ROOT/WEB-INF/classes.
If you have a fully qualified class name of com.myorg.MyServlet, then this servlet class must be located in WEB-
For now, let us copy HelloWorld.class into <Tomcat-installationdirectory>/webapps/ROOT/WEB-INF/classes and create following entries in web.xml file located in <Tomcat-installation-directory>/webapps/ROOT/WEB-INF/
Above entries to be created inside <web-app>...</web-app> tags available in web.xml file. There could be various entries in this table already available, but never mind.
You are almost done, now let us start tomcat server using <Tomcat-installationdirectory>\bin\startup.bat (on Windows) or <Tomcat-installationdirectory>/bin/startup.sh (on Linux/Solaris etc.) and finally type http://localhost:8080/HelloWorld in the browser's address box. If all goes fine, you would get the subsequent result
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