MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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252 Chapter 12: Building Custom CFXAPI Tags
What are CFX tags?
ColdFusion Extension (CFX) tags are custom tags written against the ColdFusion Extension
Application Programming Interface. Generally, you create a CFX tag if you want to do something
that is not possible in CFML, or if you want to improve the performance of a repetitive task.
One common use of CFX tags is to incorporate existing application functionality into a
ColdFusion application. That means if you already have the code available, CFX tags make it easy
to use it in your application.
CFX tags can do the following:
•
Handle any number of custom attributes.
•
Use and manipulate ColdFusion queries for custom formatting.
•
Generate ColdFusion queries for interfacing with non-ODBC based information sources.
•
Dynamically generate HTML to be returned to the client.
•
Set variables within the ColdFusion application page from which they are called.
•
Throw exceptions that result in standard ColdFusion error messages.
You can build CFX tags using C++ or Java.
Note: ColdFusion MX provides several different techniques to create reusable code, including
custom tags. For information on all of these techniques, see Chapter 8, “Reusing Code in ColdFusion
Pages,” on page 163 .
Before you begin developing CFX tags in Java
Before you begin developing CFX tags in Java, you must configure your Java development
environment. Also, you might want to take a look at some examples before creating your own
CFX tags. This section contains information about examples and how to configure your
development environment.
Sample Java CFX tags
Before you begin developing a CFX tag in Java, you might want to study sample CFX tags. You
can find the Java source files for the examples on Windows in the cfx\java\distrib\examples
subdirectory of the main installation directory. On UNIX systems, the files are located in the cfx/
java/examples directory. The following table describes the example tags:
Example Action Demonstrates
HelloColdFusion
Prints a personalized
greeting. The minimal implementation required to create
a CFX tag.
ZipBrowser Retrieves the contents of a
zip archive. How to generate a ColdFusion query and
return it to the calling page.
ServerDateTime
Retrieves the date and time
from a network server. Attribute validation, using numeric attributes,
and setting variables within the calling page.
OutputQuery
Returns a ColdFusion query
in an HTML table. How to handle a ColdFusion query as input,
throw exceptions, and generate dynamic
output.
HelloWorldGraphic
Generates a “Hello World!”
graphic in JPEG format. How to dynamically create and return graphics
from a Java CFX tag.