MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuale Utente Scaricare il pdf (Pagina 2)

2 CHAPTER 30 Extending ColdFusion with CFX

When To Write (and Avoid Writing) a CFX Tag

Given the choice between creating a CFX tag or creating a CFML-based extension such as a custom

tag, UDF, or CFC, it is generally best to consider one of the CFML-based alternatives ﬁrst. Why?

Mainly because CFML is so simple, and generally provides a rich enough feature set to get most

tasks done with ease. Whenever possible, I recommend that you consider creating a CFML-based

extension ﬁrst.

That said, there are plenty of situations where creating a CFX tag makes lots of sense. In general,

most CFX tags are created for one of the following reasons:

■

To take advantage of a third-party C++ or Java API that makes something possible that

isn’t otherwise possible in ColdFusion. Perhaps the API knows how to connect to some

kind of legacy mainframe database system, or knows how to create a special type of image

ﬁle. In this situation, the CFX tag can be thought of as wrapper around the API.

■

To take advantage of legacy code, open source code, or other snippets that have already

been written in Java or C++. If you’re working on a complex project, and you already

have Java or C++ code available that can provide part of the functionality, it may make

sense to just turn that code into a CFX tag, even if it would be possible to port the logic

to CFML. If it’s faster and easier for you and your project, go for it!

■

To take advantage of faster processing. In general, your regular ColdFusion pages are

compiled into Java classes that perform quite well. However, there will always be niche

situations where you could write custom Java or C++ code that runs more efﬁciently.

■

To circumvent method-selection problems or other errors when using Java classes (or

Beans). Most Java classes can be used via

<cfobject> or CreateObject() as discussed

in Chapter 29, “Extending ColdFusion with Java”. However, some Java methods and

constructors are overloaded in such a way that ColdFusion can’t determine which form

to use at runtime, even if you use

JavaCast(). In such a situation, you can create a CFX

tag that acts as a sort of “poor man’s proxy” between ColdFusion and the Java class.

Choosing Between C++ and Java

You can program a CFX tag in either Java or C++. Much of the time, the decision will have been

made for you, because whatever third-party API or other existing code you are planning to use will

force you to use one or the other.

The most obvious advantage to programming the CFX in Java is that it will be able to run on a

ColdFusion server using any operating system (OS). Tags created with C++, however, will need to

be recompiled for each OS you want to support. Of course, cross-platform support doesn’t mean

much if the nature of your project is such that the tag will be bound to one OS or the other anyway,

so the importance of this advantage may or may not mean a whole lot to you. For instance, if you

want the CFX tag to call native Windows APIs, then a C++ tag is the obvious choice; you’ll probably

only have to compile it once for any Win32 platform.

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MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuale Utente Pagina 2

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