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Introducing the CFX API
Another reason to use C++ is the fact that it is generally thought to be faster at extremely CPUintensive tasks. However, recent advances in Java Virtual Machine technology have made Java code
more likely than ever to perform nearly as well as comparable C++ code. Also, the ColdFusion
server can invoke Java CFXs directly, but must go through an additional layer (the Java Native
Interface, or JNI) when invoking a C++ tag. In my opinion, sheer performance issues should only
guide you toward C++ in extreme situations.
All things considered, I recommend that you go with Java if you really have a choice between the
two. The code will probably be faster, easier to write, and will almost certainly be easier to debug.
Even if you don’t anticipate using to use the tag on multiple platforms now, it will still be nice to
know that your choice of Java keeps that option open for the future.
Introducing the CFX API
Regardless of the language you use to create a CFX tag, you need a way to pass information back
and forth between the tag code and the ColdFusion page that is using the tag. You also need ways to
safely throw exceptions (errors), create query objects, and include output in the current Web page.
Macromedia defines a set of objects and functions that provides all this functionality and more. The
objects and functions are known collectively as the CFX API.
The following sections will introduce you to the various functions included in the CFX API, organized by subject. Within each section, the Java syntax will be shown in one table, followed by the
C++ syntax in a second table. You will notice that the Java and C++ versions of the API are very
similar. For the most part, there is a one-to-one relationship between the methods provided by both
versions of the API. This is great because once you design a few tags in Java, you will be well on
your way to understanding what’s possible with C++, and vice versa.
Working with the Tag’s Attributes
Like native ColdFusion tags or CFML custom tags, your CFX tags can accept any number of
attributes. You can easily add code to your tag so that some of its attributes are required while others remain optional. The CFX API defines several functions that a tag can use to accept and validate
attributes from the calling ColdFusion page. Table 30.2 shows the Java version of these functions,
and Table 30.3 shows the C++ version.
Table 30.2
Java Methods for Working with Attributes
METHOD
DESCRIPTION
request.attributeExists(name)
Determines whether the specified attribute was actually
passed to the CFX tag. Returns a boolean value.
request.getAttribute(name)
Returns the value of the specified attribute, as it was
passed to the CFX tag. Note that all attribute values are
received by the CFX as String values.
request.getAttributeList(name)
Returns the names of all attributes that were actually
passed to the CFX tag. The names are returned as an
array of strings.
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