Java Server Pages - Programming Experiments

The links listed below refer to the author's initial experiments with Java Server Pages. For the links to work properly the following requirements have to be met:

• a web server with JSP support has to be running on the local host under port number 9090 (the author is using Gefion's LiteWebServer 2.2.1 for that purpose);

• this server has to be configured such that (within the context of these JSP experiments) it processes *.htm files as JSP documents but delivers *.html files without any modification (this somewhat strange requirement comes from a limitation of the author's WYSIWYG HTML editor, which refuses to handle *.jsp files like HTML documents);

• all related Java beans and applet files have to be installed in a subdirectory where they can be found by the server (please note, that all these files belong to a package called "Acquainting", you may therefore have to create an additional subdirectory with that name and place all class files in there). A list of all required files is found at the end of this page.

Please, also consider my "Hints for Reading" and the "List of Recent Changes".

LiteWebServer Configuration

Proper setup of directories and adequate configuration of the HTTP server is essential for the JSP experiments to work properly. For that reason, this section contains any information to "install" these experiments on a LiteWebServer.

Directory Structure

Within its installation directory, the following files and (sub)folders are required for the web server to run the JSP experiments (files represented by a HTML link may be directly downloaded onto your system, other - configuration - files will have to be modified manually, as described in the next section):
 

	(LiteWebServer installation directory)
		config/ (LiteWebServer configuration directory)
			server.properties (context for JSP experiments must be added)
			JSPAcquainting/ (configuration needed for JSP experiments)
				context.properties (defines servlet context, needs modification)
				mime.properties (actually a copy of config/mime.properties)
				rules.properties (activates JSP processing)
				servlets.properties (configures JSP processing)
				session.properties (actually a copy of config/session.properties)
		servlets/ (default directory for servlet class and data files)
			JSPAcquainting/ (Java class files for the experiments)
				JSP_00_Applet.class
				JSP_00_Bean.class
				JSP_02_Bean.class
				JSP_03_Bean.class
		work/ (the server's JSP working directory)
			JSPAcquainting/ (working directory for JSP experiments)

All data files (i.e. JSP, HTML and GIF files) for the JSP experiments reside in the directory configured by "(installdir)/config/JSPAcquainting/context.properties".

LiteWebServer Configuration

In order to activate the processing of the JSP experiments on this page, the following two lines have to be added to the file (installdir)/config/server.properties:

  context.JSPAcquainting.confdir=(installdir)/config/JSPAcquainting/
  context.JSPAcquainting.uriroot=/JavaServerPages/Acquainting

In both cases, (installdir) has to be replaced by the access path for the installation directory of LiteWebServer on your local system.

Additionally, the file (installdir)/config/JSPAcquainting/context.properties must be modified as follows:

  context.docroot=(docdir)/JavaServerPages/Acquainting/

(docdir) has to be replaced by the access path for the directory into which any data files (i.e. JSP, HTML and GIF files) have been copied.

JSP Experiments

After this initial preparation, following the links shown below should work as foreseen. Please note, that you cannot test the following links over the internet - you must install a (JSP capable) HTTP server locally (as described above)!

• JSP_00 - first experiments with Java Server Pages (Output Example)
  the first "experiment" demonstrates a number of "basic" JSP features such as
  

  • insertion of an external file into the current document;
  • evaluation of a Java expression within the HTML code;
  • definition of and access to a ("persistent") variable;
  • instantiation of a JavaBean and access to its parameters and methods;
  • insertion of a Java applet independent of the actual user agent (i.e. web browser).

  The mechanisms shown on that page are rather primitive and have mainly been used to figure out how to note the various JSP directives and where to place any required Java class files;

• JSP_01 - displays the contents of several "CGI variables" (Output Example)
  the second experiment mainly represents an example for a somewhat larger JSP "scriptlet" which also includes a method that gets called from within another scriptlet.
  
  Unfortunately, the scriptlet seems to perform extremely poor (it takes approx. 30 seconds to produce a result) - at least, on the author's system (i.e., a Pentium III at 650 MHz with 128 MBytes of RAM). You may therefore have to be patient when visiting this page...

• JSP_02 - "examines" predefined JSP variables (Output Example)
  JSP_02 examines several predefined JSP variables and writes their contents into the current HTML document. Because of the performance problems with JSP "scriptlets", a JavaBean is used instead;

• JSP_03 - loads an external file and processes it (Output Example)
  this experiment simply demonstrates how to access an external file, process it and insert the result into a HTML document;

Conclusion

You might have noted the following issues:

• GIF images will be properly handled on every second JSP request only (probably because of subtle timing issues)
• JSP_00 fails to start the embedded applet
• JSP_03 crashes because of an "Out of memory" error

Because of such bad experiences with Java Server Pages, the author finished with his experiments at this stage and directed his attention to pure Servlets again (which turned out to perform much better).

Required Files

As mentioned above, a few additional files have to be installed for the experiments to work properly. The following overview lists these files:

• JSP_00.htm, JSP_01.htm, JSP_02.htm, JSP_03.htm
  these files actually contain the "Java Server Pages" behind the experiments mentioned in this document;

• JSP_00-Header.htm, JSP_00-Trailer.htm
  these two HTML files will automatically be inserted into JSP_00.htm when it gets processed by the web server;

• JSP_03.txt
  this is the plain text file which the JSP_03_Bean tries to load and embed into its HTML output;

• Line_600.gif, Paper.jpg, PaperHole.gif
  these graphics files are used to enhance the visual appearance of the author's JSP examples a bit;

Just download these files into the (docdir) configured above.

Furthermore, you might also be interested in the source code of any Java applet or JavaBean used for the JSP experiments:

• JSP_00_Bean.java
  an extremely simple JavaBean which is used to demonstrate the access to Bean variables ("properties");

• JSP_00_Applet.java
  an applet whose invocation tag is automatically created using a (brower-independent) JSP directive;

• JSP_02_Bean.java
  a simple JavaBean that accepts several predefined JSP variables and writes their contents into the current HTML document;

• JSP_03_Bean.java
  a simple JavaBean that loads a given (plain) text file, performs some encoding in order to make the text HTML-compliant and creates a preformatted paragraph for the result within the enclosing HTML document;