Programming instructions

Developing code to validate data and enforce business rules 115

Validating the existence of the trip photo file

At this point, you have a more efficient application. The client is handling much of the

validation of the Compass Travel new trip business rules. Except for the trip photo file,

the server receives only valid data.

The trip photo file business rule does not fit nicely into this design, however. The last trip

photo business rule has two parts:

• A photo file name must accompany all new trips.

• The photo image file must reside within the images directory of the Compass Travel

website.

You used the

required attribute for the photo cfinput tag to ensure that a file name is

entered. Now you must make sure that the file exists in the right directory so the

application can display it to customers.

Since browser clients are prohibited from doing standard file I/O (input/output) on the

web server, the Trips Maintenance application will use server-side validation to ensure the

existence of the photo file. You will add the business rule for the photo file to the

tripeditaction.cfm page.

To check to see if a file exists, ColdFusion provides a

FileExists function. The syntax

of this function is:

FileExists(absolute_path)

This function returns True if the file specified in the argument does exist; otherwise, it

returns

False. Assume that a data entry page has an input tag named "testFileName". If

a user types in a valid file name, the action page snippet from the following example

would display the message “The test file exists”:

<cfoutput> The test file exists. </cfoutput>

</cfif>

Note: The trip photo images are stored in the following path relative to your web root

directory: \cfdocs\getting_ started\photos. Therefore, if your web root is

C:\inetpub\wwwroot, then the photos are stored in the C:\inetpub\wwwroot\cfdocs\getting_

started\photos directory.

For more information about the FileExists function, see CFML Reference.