ColdFusion Explained
| You're now ready to take a look at ColdFusion so you can understand what it is and how it works its magic. And if you're wondering why you went through all this discussion about the Internet and Web servers, here's where it will all fit together. The ColdFusion Application ServerColdFusion is an application servera piece of software that (usually) resides on the same computer as your Web server, enabling the Web server to do things it wouldn't normally know how to do. ColdFusion is actually made up of several pieces of software (applications on Windows; and daemons on Linux and Solaris). The ColdFusion Application Server is the program that actually parses (reads and compiles) and processes any supplied instructions. Instructions are passed to ColdFusion using templates. A template looks much like any HTML file, with one big difference. Unlike HTML files, ColdFusion templates can contain special tags that instruct ColdFusion to perform specific operations. Here is a sample ColdFusion template that you'll use later in this book. <!--- Get movies sorted by release date ---> <cfquery datasource="ows" name="movies"> SELECT MovieTitle, DateInTheaters FROM Films ORDER BY DateInTheaters </cfquery> <!--- Create HTML page ---> <HTML> <HEAD> <TITLE>Movies by Release Date</TITLE> </HEAD> <BODY> <H1>Movies by Release Date</H1> <!--- Display movies in list format ---> <UL> <cfoutput query="movies"> <LI><STRONG>#Trim(MovieTitle)#</STRONG> - #DateFormat(DateInTheaters)#</LI> </cfoutput> </UL> </BODY> </HTML> Earlier in this chapter, I said that Web servers typically return the contents of a Web page without paying any attention to the file contents. That's exactly what ColdFusion doesn't do. When ColdFusion receives a request, it parses through the template looking for special ColdFusion tags (they all begin with CF) or ColdFusion variables and functions (always surrounded by number [#] signs). HTML or plain text is left alone and is output to the Web server untouched. Any ColdFusion instructions are processed, and any existing results are sent to the Web server (just like in Figure 1.6 above). The Web server can then send the entire output back to the requester's browser. As explained earlier, the request file type tells the Web server that a request is to be handled by an application server. All ColdFusion files have an extension of .cfm or .cfml, like this: http://www.forta.com/books/index.cfm When ColdFusion is installed, it configures your Web server so it knows that any file with an extension of .cfm (or .cfml) is a ColdFusion file. Then, whenever a ColdFusion file is requested, the Web server knows to pass the file to ColdFusion for processing rather than return it. It's worth noting that ColdFusion MX doesn't actually need a Web server because it has one built in. So as not to conflict with any other installed Web servers (like Apache and Microsoft IIS) the internal Web server runs on port 8500 or 8300 (depending on the type of installation performed) instead of the default port 80. During ColdFusion MX installation you'll be asked whether you want to run ColdFusion in stand-alone mode (bound to the integrated Web server) or using an existing Web server. If you opt to use the internal Web server you'll need to specify the port number in all URLs. NOTE The examples in this book use the internal Web server, so they include the port number. If you're using an external Web server, just drop the port number from the URLs. TIP Macromedia doesn't recommend that the internal Web server (stand-alone mode) be used on production boxes. ColdFusion MX's integrated HTTP server is intended for use on development boxes only. The ColdFusion Markup LanguageI said earlier that ColdFusion is an application server; that's true, but that's not all it is. In fact, ColdFusion is two distinct technologies:
Although the ColdFusion Application Server itself is important, ColdFusion's power comes from its capable and flexible language. ColdFusion Markup Language (CFML) is modeled after HTML, which makes it very easy to learn. CFML extends HTML by adding tags with the following capabilities:
And that's not even the complete list. The majority of this book discusses ColdFusion pages (often called templates) and the use of CFML. Linking to External ApplicationsOne of ColdFusion's most powerful features is its capability to connect to data created and maintained in other applications. You can use ColdFusion to retrieve or update data in many applications, including the following:
ColdFusion accesses these applications via database drivers (JDBC and ODBC).
Extending ColdFusionAs installed, ColdFusion will probably do most of what you need, interacting with most of the applications and technologies you'll be using. But in the event that you need something more, ColdFusion provides all the hooks and support necessary to communicate with just about any application or service in existence. Integration is made possible via:
These technologies and their uses are beyond the scope of this book and are covered in detail in the sequel, Advanced ColdFusion MX 7 Application Development (Macromedia Press, ISBN: 0-321-29269-3). Beyond the WebAs explained earlier, the Web and the Internet aren't one and the same. The Web is an application that runs on top of the Internet, one of many applications. Others exist, and you can use and take advantage of many of them. One of the most exciting new technologies is Wireless Application Protocol (WAP), which can be used to power applications accessed via wireless devices (such as phones and PDAs). As explained earlier, Web servers (and thus application servers) send content back to requesters without paying attention to what that content is. The requester (known as the client or user agent) is typically a Web browser, but it need not be. In fact, WAP browsers (the Internet browsers built into WAP devices) can also make requests to Web servers.
In other words, although ColdFusion is primarily used to generate Web content, it isn't limited to doing so in any way, shape, or form. As seen in Figure 1.7, the same server can generate content for the Web, WAP, email, and more. Figure 1.7. ColdFusion is client independent and can generate content for many types of clients, not just Web browsers.
Inside ColdFusion MX 7ColdFusion MX 7 is the most remarkable ColdFusion to date, and is built on top of ColdFusion MX, the first completely redesigned and rebuilt ColdFusion since the product was first created back in 1995. Understanding the inner workings of ColdFusion MX isn't a prerequisite to using the product, but knowing what ColdFusion is doing under the hood will help you make better use of this remarkable product. I said earlier that ColdFusion is a page preprocessorit processes pages and returns the results as opposed to the page itself. To do this ColdFusion has to read each file, check and validate the contents, and then perform the desired operations. But there is actually much more to it than that. In fact, within ColdFusion is a complete J2EE (Java 2 Enterprise Edition) server that provides the processing power ColdFusion needs. NOTE Don't worry, you don't need know any Java at all to use ColdFusion. First, a clarification. When people talk about Java they generally mean two very different things:
Of the two, the former is of no interest (well, maybe little interest) to ColdFusion developers. After all, why write complex code in Java to do what CFML can do in a single tag? But Java the platform? Now that's compelling. The Java platform provides the wherewithal to:
In the past you'd have had to write Java code in order to leverage the Java platform, but not any more. ColdFusion MX runs on top of the Java platform, providing the power of underlying Java made accessible via the simplicity of CFML. NOTE By default, the Java engine running ColdFusion MX 7 is Macromedia's own award-winning J2EE server, JRun. ColdFusion MX 7 can also be run on top of third-party J2EE servers like IBM's WebSphere and BEA's WebLogic. See Appendix A, "Installing ColdFusion and Dreamweaver" for more information. But don't let the CFML (and CFM files) fool youwhen you create a ColdFusion application you are actually creating a Java application. In fact, when ColdFusion processes your CFM pages it actually creates Java source code and compiles it into Java bytecode for you, all in the background. This behavior was first introduced in ColdFusion MX. Using ColdFusion you can truly have the best of both worldsthe power of Java, and the simplicity of ColdFusion, and all without having to make any sacrifices at all.
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Database drivers are explained in detail in Chapter 6, "Introducing SQL."
EAN: N/A
Pages: 282