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">

Recommended uses

CFX tags provide one way of using C++ or Java code. However, you can also create Java classes and COM objects and access them using the cfobject tag. CFX tags, however, provide some built-in features that the cfobject tag does not have:

• CFX tags are easier to call in CFML code. You use CFX tags directly in CFML code as you would any other tag, and you can pass arguments using a standard tag format.
• ColdFusion provides predefined classes for use in your Java or C++ code that facilitate CFX tag development. These classes include support for request handling, error reporting, and query management.

You should consider using CFX tags in the following circumstances:

• You already have existing application functionality written in C++ or Java that you want to incorporate into your ColdFusion application.
• You cannot build the functionality you need using ColdFusion elements.
• You want to provide the new functionality in a tag format, as opposed to using the cfobject tag to import native Java or COM objects.
• You want use the Java and C++ classes provided by ColdFusion for developing your CFX code.

For more information

For more information on CFX tags, see Building Custom CFXAPI Tags.