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438 Chapter 3: ColdFusion Functions

CreateUUID

Description

Creates a Universally Unique Identifier (UUID). A UUID is a 35-character string representation

of a unique 128-bit integer.

Returns

A ColdFusion format UUID, in the format xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxxx, where x

is a hexadecimal digit (0-9 or A-F). (The character groups are 8-4-4-4-16.)

Category

Other functions

Function syntax

CreateUUID()

Usage

The ColdFusion UUID generation algorithm uses the unique time-of-day value, the IEEE 802

Host ID, and a cryptographically strong random number generator to generate UUIDs that

conform to the principles laid out in the draft IEEE RFC "UUIDs and GUIDs."

The ColdFusion UUID format is as follows:

xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxxx (8-4-4-16).

This does not conform to the Microsoft/DCE standard, which is as follows:

xxxxxxxx-xxxx-xxxx-xxxxxx-xxxxxxxxxx (8-4-4-4-12)

There are UUID test tools and a user-defined function called CreateGUID, which converts

CFML UUIDs to UUID/Microsoft GUID format, available on the web at www.cflib.org.

Use this function to generate a persistent identifier in a distributed environment. To a very high

degree of certainty, this function returns a unique value; no other invocation on the same or any

other system returns the same value.

UUIDs are used by distributed computing frameworks, such as DCE/RPC, COM+, and

CORBA. In ColdFusion, you can use UUIDs as primary table keys for applications in which data

is stored in shared databases. In such cases, using numeric keys can cause primary-key constraint

violations during table merges. Using UUIDs, you can eliminate these violations.

Example

<h3>CreateUUID Example</h3>

<p> This example uses CreateUUID to generate a UUID when you submit the form.

You can submit the form more than once. </p>

<hr>

<p>Your new UUID is: <cfoutput>#CreateUUID()#</cfoutput></p>

</cfif>

</form>