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Introducing ASP+

Even though the ink is barely dry on the documentation for Active Server Pages 3.0, Microsoft is already hard at work on the next generation of their core server-side programming technology. In this chapter, we introduce this new product, and look at what it is all about. Currently called ASP+ Next Generation Web Services (though this name might yet change) we'll see why we need a new version of ASP, and explore the concepts behind its design and implementation. While this book is aimed predominantly at experienced developers who have used ASP before, we start out in this chapter by examining some of the core issues involved when you decide to migrate to ASP+.

 

ASP+ is designed to be backwards-compatible with earlier versions of ASP, with only minor changes required in some circumstances (we explore these further in the appendices). However, more to the point, you can install ASP+ on an existing Windows 2000 server alongside ASP 3.0. This allows you to experiment with the new version, without requiring a separate 'test bed' server. You can continue using existing ASP applications, and migrate them ASP+ when you are ready, so your investment in ASP is not lost.

 

But simply porting your applications to ASP+ will only give you a few of the benefits the new version offers. ASP+ has many new features that provide far greater ease of use, more power and better
runtime efficiency, but to take advantage of them you will need to understand more about the way
that ASP+ works
.

 

As we are writing this book using a preview version of ASP+, we can't be exactly sure of all the features of the final release. But thanks to the information and assistance provided by the ASP+ team at Microsoft, we can be pretty sure that the content of the book will be reliable and useful with the final version. We'll also be maintaining a special Web site that is accessible from http://www.wrox.com/beta, where we'll document changes as the beta and final release versions appear, and provide some detailed information as well.

 

So, in this first chapter, we'll cover:

 

q         How Active Server Pages has evolved since its inception

q         What the new runtime framework is

q         How ASP+ is different to ASP, and why

q         A brief guide to getting started with ASP+

q         Some of the changes expected in the final release version

 

We start with a look at the way that ASP and ASP+ have evolved, as this will help to set the background for understanding and working with the new product. For more information about working with COM+ and previous versions of ASP, check out Professional ASP 3.0, (ISBN 1-861002-61-0) from Wrox.

The Evolution of Active Server Pages

Although it seems to have been around forever, Active Server Pages is only some three-and-a-bit years old. Since its inception in late 1996, it has grown rapidly to become the major technique for server-side Web programming in the Windows environment (and on some other platforms using other implementations that accept the same or similar syntax, such as ChilliASP). But it didn't come from nowhere the foundations lie much further back than that.

Dynamic Server-side Web Programming

Traditionally, dynamic Web pages have been created using server-side executable programs. A standardized Web server interface specification called the Common Gateway Interface (CGI) allows an executable program to access all the information within incoming requests from clients. The program can then generate all the output required to make up the return page (the HTML, script code, text, etc.), and send it back to the client via the Web server.

 

To make the programmer's life easier, and save having to create executable programs, languages such as Perl use an application that accepts text-based script files. The programmer simply writes the script, and the Web server executes it using a Perl interpreter.

Microsoft ISAPI Technologies

Microsoft introduced another Web server interface with their Web server, Internet Information Server. This is the Internet Server Application Programming Interface (ISAPI), and differs from the CGI in that it allows compiled code within a dynamic link library (DLL) to be executed directly by the Web server. As with the CGI, the code can access all the information in the client request, and it generates the entire output for the returned page.

 

Most developments in Microsoft's Web arena have been based on the ISAPI interface. One early and short-lived product was dbWeb, a data access technology that provided a range of searching, filtering and formatting capabilities for accessing data stored on the server, and for interacting with the client.

 

A second development was the Internet Database Connector (IDC). This proved a big hit with developers not only because it was fast and efficient (unlike dbWeb), but also because it was a lot more generic and easier to program. IDC introduced the concept of templates, allowing programmers to easily adapt existing HTML pages to use its features and quickly build new applications around it.


IDC uses two text files for each 'page'. The first is a simple script that defines the way that the data should be collected from the server-based database. In essence, it is just a SQL statement plus some configuration information:

 

{this is the query file named getuserlist.idc}

Datasource: GlobalExampleData

Username: examples

Password: secret

Template: getuserlist.htx

SQLStatement:

+ SELECT DISTINCT UserName

+ FROM Person ORDER BY UserName;

 

The server executes this file to obtain the results recordset, then loads a template file:

 

{this is an extract from the template file named getuserlist.htx}

...

<TABLE>

<TR>

<TD>User name:</TD>

<TD>

<SELECT NAME=selUserName>

<%BeginDetail%>

<OPTION VALUE="<%UserName%>"><%UserName%>

<%EndDetail%>

</SELECT>

</TD>

</TR>

</TABLE>

...

 

The template is just an ordinary Web page, including HTML, text and other objects, but with one or more specially delimited placeholders inserted. And the syntax for these placeholders, and the other simple program code constructs that are supported, is eerily like ASP. Of course, it was from this that ASP actually evolved:

The Versions of ASP

So, it was in early 1996 that Denali (the codename for ASP) was released as a beta version 0.9 product, and it took the Web-development world by storm. The ability to execute code inline within a Web page was so simple and yet so powerful. With the provision of a series of components that could perform advanced features, most notably ActiveX Data Objects (ADO), it was almost child's play to create all kinds of dynamic pages.

 

The final release version of Active Server Pages 1.0, available as an add-on for IIS 3.0, was soon in use on Windows platforms all over the place. The combination of ASP with ADO enabled developers to easily create and open recordsets from a database. There's no doubt that this was one of the main factors for its rapid acceptance, because now you could create and open recordsets from a database within the script, and manipulate and output any values, in any order, almost any way you wanted.

 

In 1998, Microsoft introduced ASP 2.0 as part of the free Windows NT4 Option Pack. The major difference between this release of ASP and version 1.0 was in the way that external components could be instantiated. With ASP 2.0 and IIS 4.0, it is possible to create an ASP application, and within it run components in their own separate memory space (i.e. out of process). The provision of Microsoft Transaction Server (MTS) also made it easy to build components that can partake in transactions.

 

Windows 2000, COM+, and ASP 3.0

Early this year (2000), Windows 2000 arrived. This contains version 5.0 of IIS, and version 3.0 of ASP. Other than some minor additions to ASP, the core difference here is actually more to do with COM+. In Windows 2000, Microsoft combined MTS with the core COM runtime to create COM+. This provides a host of new features that make the use of components easier, as well as giving a much more stable, scalable and efficient execution platform.

 

Other than a few minor changes to the management interface, IIS has not changed a great deal on the surface. However, underneath, it now uses COM+ Component Services to provide a better environment for components to be executed within, including out of process execution as the default and the option to run each component in its own isolated process if required.

ASP+ and the Next Generation Web Services Framework

All this brings us to the present, with ASP+. The underlying structure of ASP+ is very different to that of previous versions, although from the 'outside' (as far as the developer is concerned) it does appear to offer a very similar interface. ASP+ is almost entirely component-based and modularized, and every page, object, and HTML element you use can be a runtime component object.

 

For this to perform efficiently, and provide a scalable solution, the management of these objects is a very necessary prerequisite. The new runtime environment carries out this management automatically, allowing ASP+ to become far more object-oriented in nature. This lets developers build more powerful applications by accessing these component objects in a far more granular and controlled manner.

 

On top of that, the object orientation of ASP+ provides extensibility for the environment as a whole. Developers can add to and extend the environment, both by creating new components or inheriting from the base classes that create them, and by over-riding selected behavior as required. Under the hood, the COM+ runtime manages the instantiation, pooling, and allocation of the objects automatically.


©1999 Wrox Press Limited, US and UK.
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