Server-Side Technologies For Providing Dynamic Content
Each of these technologies relies on a modular attachment added
onto the web server rather than the browser. Consequently, only HTML, and any client-side
script, is sent back to the browser by the web server. In other words, none of the
server-side code is sent back. Server-side technologies have a more consistent look
and feel than client-side ones, and it doesn't take that much extra learning to
move between some of the server-side technologies (excepting CGI).
CGI
The Common Gateway Interface (CGI) is a mechanism for creating
scripts on the server, which can then be used to create dynamic web applications.
CGI is a module that is added to the web server. It has been around for quite a
bit longer than even ASP, and right now, a large proportion of dynamically created
web pages are created using CGI and a scripting language. However, it's incorrect
to assume that CGI does the same job as ASP.NET or ASP. Rather, CGI allows the user
to invoke another program (such as a Perl script) on the web server to create the
dynamic web page, and the role of CGI is to pass the user supplied data to the this
program for processing. However, it does provide the same end result – a dynamic
web application.
You should be aware that CGI has some severe shortcomings:.
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It is not easy for a beginner to learn how to program such modules.
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CGI requires a lot of server resources, especially in a multiuser situation.
-
It adds an extra step to our server–side model of creating dynamic content:
namely, it's necessary to run a CGI program to create the dynamic page, before the
page is processed on the server.
What's more, the format in which CGI receives and transmits data means that the
data is not easily manipulated by many programming languages, so you need one with
good facilities for manipulating text and communicating with other software. The
most able programming languages that can work on any operating system for doing
this are C, C++ and Perl. While they can adequately do the job for us, they are
some of the more complex languages to learn. Visual Basic doesn't offer adequate
text handling facilities, and is therefore rarely used with CGI.
Despite this, CGI is still very popular with many big web sites, particularly those
running on UNIX operating systems. It also runs on many different platforms, which
will ensure its continued popularity.
ASP
Active Server Pages (ASP) is now dubbed "Classic
ASP" and if you see this term in the book, we will be using it to describe
any ASP that isn't ASP.NET. ASP commonly relied on either of the JavaScript or VBScript
scripting languages (although it was also possible to use any scripting language
installed on Windows, such as PerlScript) to create dynamic web pages. ASP is a
module (the asp.dll file) that you attach to your web server, and it then processes
the JavaScript/VBScript on the web server, and turns it into HTML, before sending
it into the server, rather than doing it on the browser.
ASP lets us use practically any of the functionality provided by Windows, such as
database access, e-mailing, graphics, networking, and system functions, and all
from within a typical ASP page. However, ASP's shortcomings are that it is very,
very slow performance wise. It is also restricted to using only scripting languages.
It can't do all the things that a fully-fledged programming language can. Secondly,
the scripting languages, being like "junior" versions of full programming
languages, took a lot of shortcuts to make the language smaller. Some of these shortcuts
make their programs longer and more complicated than is otherwise necessary. As
we're going to see, ASP.NET rectifies a lot of this by making code more structured,
easier to understand, and shorter.
JSP
JavaServer Pages (JSP) is a technology that allows
you to combine markup (HTML or XML) with Java code to dynamically generate web pages.
The JSP specification is implemented by several web servers, as opposed to ASP which
is only supported under IIS, and plug-ins are available that allow you to use JSP
with IIS 4.0/5.x. One of the main advantages of JSP is the portability of code between
different servers. JSP is also very powerful, faster than ASP, and instantly familiar
to Java programmers. It allows the Java program to leverage the aspects of the Java2
platform such as JavaBeans and the Java 2 libraries. JavaServer Pages isn't directly
related ASP, but it does boast the ability to embed Java code into your web pages
using server-side tags. More details can be found at the official site at http://www.javasoft.com/products/jsp/index.html
and at the JSP FAQ at http://www.esperanto.org.nz/jsp/jspfaq.html.
ColdFusion
ColdFusion (http://www.macromedia.com/software/coldfusion/)
also enables servers to access data as the server builds an HTML page. ColdFusion
is a module installed onto your web server. Like ASP, ColdFusion pages are readable
by any browser. ColdFusion also utilizes a proprietary set of tags, which are processed
by the ColdFusion Server software. This server software can run on multiple platforms,
including IIS, Netscape Enterprise Server and Unix/Apache. The major difference
is that while ASP.NET solutions are built primarily with programming languages and
objects, ColdFusion utilizes HTML-like tags, which encapsulate functionality. A
drawback is that the ColdFusion software doesn't come for free and indeed you could
find yourself paying well in excess of a thousand dollars for the privilege of running
Cold Fusion on your web server.
PHP
PHP (originally Personal Home Pages, but more recently PHP
HyperText Preprocessor) is another scripting language for creating dynamic web pages.
When a visitor opens the page, the server processes the PHP commands and then sends
the results to the visitor's browser, just as with ASP.NET or ColdFusion. Unlike
ASP.NET or ColdFusion, however, PHP is open-source and cross-platform. PHP runs
on Windows NT and many Unix versions, and it can be built as an Apache module and
as a binary that can run as a CGI. When built as an Apache module, PHP is especially
speedy. A downside is that you have to download PHP separately and go through a
series of quite complex steps to install it and get it working on your machine.
Also PHP's session management was non-existent until PHP 4, and still is even now,inferior
to ASP's even now.
PHP's language syntax is similar to C and Perl. This might prove a barrier to people
with no prior programming experience, but if you have a background in either language
then you might want to take a look. PHP also has some rudimentary object-oriented
features, providing a helpful way to organize and encapsulate your code. You can
find more information about PHP at http://www.php.net.
ASP.NET
So why are you telling me about all these other technologies
if we're only going to be learning about ASP.NET you might be wondering? Hopefully
you'll see a similarity between the technologies, and this will aid your understanding
of ASP.NET.
ASP.NET also relies on a module attached to the web server. However, the ASP.NET
module (which is a physical file called aspnet_isapi.dll) doesn't do all of the
work itself; it passes some on to the .NET Framework to do the processing for it.
Rather than going into ASP.NET in this subsection here, it's time to start talking
about it as a separate entity in its own right, as this is the focus of the book.
What is ASP.NET?
We're going to be asking this question a lot throughout the book,
and each time we ask it, we're going to give you a slightly more in-depth answer.
If we were we to give you a full answer now, you'd be overwhelmed by as-yet meaningless
jargon. So, you'll probably be aware of some unanswered questions each time we describe
it.
Our original definition, right at the very start of the chapter, was "ASP.NET
is a new and powerful technology for creating dynamic web pages", and this
still holds true. However, as you now know, it isn't the only way to deliver dynamic
web pages, so let's refine our definition a little to read:
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A new and powerful server-side technology for creating dynamic web pages.
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Secondly, ASP.NET isn't the only thing that we're interested in. In fact, it's one
of a set of technologies that comprise the Microsoft .NET Framework. For now, you
can think of this as a giant toolkit for creating all sorts of applications, and
in particular, for creating applications on the Web. When we come to install ASP.NET,
we will also be installing the .NET Framework at the same time, and we'll be using
bits and pieces of the .NET Framework throughout the book.
How does ASP.NET differ from ASP?
Steady on! We're just getting to this part. ASP, as we've said
is restricted to using scripting languages, mainly JavaScript or VBScript (although
it can be any scripting language supported by the Windows system). We add ASP code
to our pages in the same way as we do client-side script, and this leads to problems
such as messy coding and restricted functionality. ASP.NET has no such problems.
First off ASP.NET allows you to use a far greater selection of full programming
languages and also allows you to utilize to the full the rich potential of the .NET
Framework. It helps you create faster, more reliable dynamic web pages with any
of the programming languages supported by the .NET Framework. Typical languages
supported natively are VB.NET, C# and a new version of JavaScript called JScript.NET.
On top of this it is expected that third party developers will create versions of
Perl, Python, and many others to work in ASP.NET. And no, before you ask, we don't
expect you to be know any of these programming languages. We're going to choose
one language, VB.NET, and teach you ASP.NET with it. We've chosen VB.NET as it's
arguably the simplest for beginners, and it can do pretty much anything that the
other languages we mentioned can as well. Lastly, and most importantly we've chosen
VB.NET as it comes free with ASP.NET – so when you install ASP.NET you get
VB.NET as well.
At this stage, you might be thinking, "Hang on, I've got to figure out VB.NET,
then I've got to get a handle on ASP.NET – that sounds like an awful lot to
learn." Don't worry; you won't be learning two languages. ASP.NET, as we said
right from the beginning, is not a language – it is a technology. This technology
is accessible, via a programming language. What we're going to be doing is teaching
you ASP.NET features as we teach you VB.NET. So in other words, you will be creating
your web pages using VB.NET and using ASP.NET to drive it. However, before you rush
out and get a VB.NET book instead, we will be approaching the language from the
angle of creating dynamic web pages only.
In summation, ASP.NET is a server-side technology that lets us use fully-fledged
programming languages to create your web pages.
I'm still confused about ASP, ASP.NET, and VB.NET
It's really important to get these terms separate and distinct
in your mind, so before we move on to actually installing and running ASP.NET, we're
going to go back and redefine them just to make sure:
- ASP – a server-side technology for creating dynamic web pages that only lets
you use scripting languages
- ASP.NET – a server-side technology for creating dynamic web pages that lets
you use any fully-fledged programming language supported by .NET
- VB.NET – our chosen programming language for writing code in ASP.NET
Now it's time to get it all installed.
The Installation Process
Installation is going to be done in three steps. We're going
to install the web server first, next, we're going to install the prerequisites
required for ASP.NET to work, and then, lastly, we're going to install ASP.NET Premium
Edition or .NET Framework SDK (which also contains ASP.NET).
Anybody who is familiar with ASP might be used to it being installed automatically
with the web server, and thereby doing it all in one step. This is true – classic
ASP is still installed with the web server, however ASP.NET currently is only available
as a separate download. This means you will have to download ASP.NET from Microsoft's
web site or from CD (if you have one). However, before you can install ASP.NET,
it is necessary to have a working web server.
If you have installed IIS 5.x already, or have installed either the Windows 2000
Server or Advanced Server operating system, then the good news is that you can skip
this section, and go straight onto the section about installing the .NET Framework.
However for the rest of us, you will have to pay careful attention to the next section.
Installing the IIS 5.x Web Server
We'll look at the installation process for IIS on Windows 2000
Professional and Windows XP Professional together, as they don't differ significantly.
The main difference is that Windows 2000 installs IIS 5.0, while Windows XP installs
IIS 5.1. The options for installing are exactly the same, the only thing that might
differ is the look of the dialog boxes. However, the options you need to select
are still the same.
Before you install it though, it's worth noting that we might not have to do much
in this initial stage, as it's possible you're already running IIS 5.x. We'll describe
a process for checking whether this is the case as part of the installation process.
You should also note that to install anything (not just ASP.NET, but literally anything)
on Windows 2000/XP you need to be logged in as a user with administrative rights.
If you're uncertain of how to do this, we suggest you consult your Windows documentation.
Right let's get started!
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Try It Out – Locating and/or installing IIS 5.x
on my Web Server machine
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- Go to the control panel (Start | Settings | Control Panel) and select the Add/Remove
Programs icon. The following dialog will appear, displaying a list of your currently
installed programs:
- Select the Add/Remove Windows Components icon on the left side of the dialog,
to get to the screen that allows you to install new windows components:
- Locate the Internet Information Services (IIS) entry in the dialog, and note the
checkbox that appears to its left. Unless you installed Windows 2000 via a custom
install and specifically requested IIS, it's most likely that the checkbox will
be unchecked (as shown above).
- If the checkbox is cleared, then check the checkbox and click on Next to load
Internet Information Services 5.x. You might be prompted to place your Windows 2000/XP
installation disk into our CD-ROM drive. It will take a few minutes to complete.
Then go to Step 5.
OR
If the checkbox is checked then you won't need to install the IIS 5.x component
– it's already present on your machine. Go to Step 6 instead.
- Click on the Details button – this will take you to the dialog shown below.
There are a few options here, for the installation of various optional bits of functionality.
For example, if the World Wide Web Server option is checked then our IIS installation
will be able to serve and manage web pages and applications. If you're planning
to use FrontPage 2000 or Visual InterDev to write your web page code, then you'll
need to ensure that the FrontPage 2000 Server Extensions checkbox is checked. The
Internet Information Services Snap-In is also very desirable, as you'll see later
in the chapter, so ensure that this is checked too:
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For the purpose of this installation, make sure all the checkboxes in this dialog
are checked; then click on OK to return to the previous dialog.
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- There's one other component that we'll need to install, for use later in this
book – it's the Script Debugger. If you scroll to the foot of the Windows Components
Wizard dialog that we showed above, you'll find a checkbox for Script Debugger.
If it isn't already checked, check it now and click on Next to complete the installation.
Otherwise, if both IIS 5.x and the script debugger are already present, you can
click on Cancel to abort the process:
How It Works
Web Services starts up automatically as soon as your installation
is complete, and thereafter, whenever you boot up Windows – so you don't need
to run any further startup programs, or click on any short-cuts as you would to
start up Word or Excel.
IIS installs most of its bits and pieces on your hard drive, under the \WinNT\system32\inetsrv
directory; however, more interesting to us at the moment is the \InetPub directory
that is also created at this time. This directory contains subdirectories that will
provide the home for the web page files that we create.
If you expand the InetPub directory, you'll find that it contains several subdirectories:
- \iissamples\homepage contains some example classic ASP pages
- \iissamples\sdk contains a set of subdirectories that hold classic ASP pages which
demonstrate the various classic ASP objects and components.
- \scripts is an empty directory, where ASP.NET programs can be stored.
- \webpub is also empty. This is a 'special' virtual directory, used for publishing
files via the Publish wizard. Note that this directory only exists if you are using
Windows 2000 Professional Edition.
- \wwwroot is the top of the tree for your web site (or web sites). This should
be your default web directory. It also contains a number of subdirectories, which
contain various bits and pieces of IIS. This directory is generally used to contain
subdirectories which hold the pages that make up our web site – although, in
fact, there's no reason why you can't store your pages elsewhere. We'll be discussing
the relationship between physical and virtual directories later in this chapter.
- \ftproot, \mailroot and \nntproot should form the top of the tree for any sites
that use FTP, mail, or news services, if installed.
- In some versions of Windows , you will find an \AdminScripts folder which contains
various VBScript files for performing some common "housekeeping" tasks
on the web server, allowing you to stop and start services.
Working with IIS
Having installed
IIS web server software onto our machine, we'll need some means of administering
its contents and settings. In this section, we'll meet the user interface that is
provided by IIS 5.x.
In fact, some versions of IIS 5.x provide two user interfaces the MMC, and the PWS
interface. We're only going to look at one, as the other version is now obsolete.
The version we will use is the Microsoft Management Console (MMC) that is a generic
way of managing all sorts of services. Let's take a quick look at it now.
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