Articles : Java Networking :

Writing Servlets

Compiling Hello, Browser!

OK, now that you have this HelloBrowser.java source code in place, you can compile it. This is as simple as using the following command:

javac HelloBrowser.java

Did you get the following error?

HelloBrowser.java:4: Package javax.servlet
   not found in import.
import javax.servlet.*;
       ^
HelloBrowser.java:5: Package
   javax.servlet.http not found in import.
import javax.servlet.http.*;
       ^
HelloBrowser.java:7: Superclass HttpServlet
   of class HelloWorld not found.
public class HelloWorld extends HttpServlet {
                                ^
HelloBrowser.java:7: Public class
   HelloWorld must be defined in a file
   called "HelloWorld.java".
public class HelloWorld extends HttpServlet {
             ^
4 errors

This is a common mistake. It means that you did not set up your Java CLASSPATH to include the servlet.jar Servlet API. Go back to the previous section on setting up the development environment and make sure that the CLASSPATH has been set up properly.

If you want to double check the value of your CLASSPATH, you can find out what your current CLASSPATH value is by typing the following at a DOS prompt:

echo %CLASSPATH%

If the CLASSPATH is set properly, you should see something similar to the following:

c:\jdk1.2.2\lib\tools.jar;c:\jswdk-1.0.1\lib\servlet.jar

Once you are sure that have the CLASSPATH set to include the original CLASSPATH plus the servlet.jar file, you can go back to compiling the HelloBrowser servlet. Then, when the HelloBrowser class file is compiled, copy it to the tutorial\WEB-INFO\servlets directory. Next, use your browser to launch the URL: http://localhost:8080/tutorial/servlet/HelloBrowser.

At this point, you should see a message appear on your browser similar to the one below. My browser field was replaced with a string relevant to Internet Explorer v5.0 on Windows 98 because that is the browser that I used to test the script. If you are using a different browser version, operating system, or brand of browser, then you will get a different browser string than the one below.

Hello, Mozilla/4.0 (compatible; MSIE 5.0; Windows 98; DigExt)!

NEXT

Gunther Birznieks contributes to JavaBoutique's Web/Networking column. Gunther currently works for Barclays Capital in London, one of the leading global investment banks in Europe and has previously worked as a senior computer scientist in the Human Genome Project. Gunther is also known for writing several books on Web Programming (Perl, CGI, Java) as well as for co-creating Extropia with Selena Sol. Extropia is one of the best known public domain web programming archives Email: gunther@extropia.com.

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