MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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Using CFX tags 169
Recommended uses
ColdFusion custom tags let you abstract complex code and programming logic into simple units.
These tags let you maintain a CFML-like design scheme for your code. You can easily distribute
your custom tags and share tags with others. For example, the Macromedia ColdFusion
Developer’s Exchange includes a library of custom tags that perform a wide variety of often-
complex jobs; see http://devex.macromedia.com/developer/gallery/index.cfm.
Consider using CFML custom tags in the following circumstances:
•
You need a tag-like structure, which has a body and an end tag, with the body contents
changing from invocation to invocation.
•
You want to associate specific processing with the beginning tag, the ending tag, or both tags.
•
To use a logical structure in which the tag body uses “child” tags or subtags. This structure is
similar to the
cfform
tag, which uses subtags for the individual form fields.
•
You do not need a function format in which the calling code uses a direct return value.
•
Your code must be recursive.
•
Your functionality is complex.
•
To distribute your code in a convenient form to others.
If you can create either a UDF or a custom CFML tag for a purpose, first consider creating a
UDF because invoking it requires less system overhead than using a custom tag.
For more information
For more information on custom CFML tags, see Chapter 9, “Creating and Using Custom
CFML Tags,” on page 173 .
Using CFX tags
ColdFusion Extension (CFX) tags are custom tags that you write in Java or C++. Generally, you
create a CFX tag to do something that is not possible in CFML. CFX tags also let you use existing
Java or C++ code in your ColdFusion application. Unlike CFML custom tags, CFX tags cannot
have bodies or ending tags.
CFX tags can return information to the calling page in a page variable or by writing text to the
calling page.
CFX tags can do the following:
•
Have any number of custom attributes.
•
Create and manipulate ColdFusion queries.
•
Dynamically generate HTML to be returned to the client.
•
Set variables within the ColdFusion page from which they are called.
•
Throw exceptions that result in standard ColdFusion error messages.
Calling CFX tags
To use a CFX tag, precede the class name with cfx_ and put the name in angle brackets. For
example, use the following line to call the CFX tag defined by the MyCFXClass class and pass it
one attribute.
<cfx_MyCFXClass myArgument="arg1">