Coldfusion 8 - Best practice for DAO AJAX access? - ajax

Question

I'm fairly new to using OO concepts such as DAO's, Gateways etc and I'm trying to work out the best way to implement an AJAX accessible CFC whilst trying not to repeat lot's of code.
I have the following DAO which holds CRUD methods for my DB table and takes the application DSN as an argument in it's constructor:
<cfcomponent name="property_imageDAO" displayname="property_imageDAO" output="false" hint="">
<!--- pseudo constructor --->
<cfscript>
variables.dsn = application.dsn;
</cfscript>
<!--- constructor --->
<cffunction name="init" access="public" output="false" returntype="any"
hint="Constructor for this CFC">
<!--- take DSN as argument --->
<cfargument name="dsn" type="string" required="true" hint="The datasource name" />
<!--- put dsn in variables scope so we can use it throughout the CFC --->
<cfset variables.dsn = arguments.dsn />
<!--- return this CFC --->
<cfreturn this />
</cffunction>
<!--- CRUD methods (create, read, update, delete) --->
<!--- CREATE: inserts a new property_image into the database --->
<cffunction name="createRecord" access="remote" output="true"
hint="Creates a new property_image record and returns a struct containing a boolean (success) indicating the success or
failure of the operation, an id (id), and a string (message) containing a message">
<!--- take property_image bean as argument --->
<cfargument name="property_image" type="any" required="true" />
<!--- initialize variables --->
<cfset var results = StructNew() />
<cfset var qInsertproperty_image = 0 />
<!--- defaults --->
<cfset results.success = true />
<cfset results.message = "The record was inserted successfully." />
<!--- insert the property_image --->
<cftry>
<cfquery name="qInsertproperty_image" datasource="#variables.dsn#">
INSERT INTO property_image (
name,
alt
)
VALUES (
<cfqueryparam value="#arguments.property_image.getname()#" cfsqltype="cf_sql_varchar" />,
<cfqueryparam value="#arguments.property_image.getalt()#" cfsqltype="cf_sql_varchar" />
)
</cfquery>
<cfcatch type="database">
<cfset results.success = false />
<cfset results.message = "Inserting the record failed. The error details if available are as follows: " & CFCATCH.Detail />
</cfcatch>
</cftry>
<!--- return the struct --->
<cfreturn StructCopy(results) />
</cffunction>
Should I add functionality to this DAO to make it AJAX accessible or should I create another DAO specifically for remote access?
Thanks

Answer 1

I think there's probably as many variations of a solution to this as there will be people to suggest one, but here's one take on it.
I'd not openthe DAO up to REMOTE access, I'd leave that as PACKAGE (and only be accessed by some business object in the same package). I'd also have some sort of facade sitting in front of that lot which handles the remote calls, as well as things like validating whether the call coming in remotely IS ALLOWED to be making the call. You don't want just anyone sticking stuff in your DB! The facade should deal with the auth side of things, then if all OK pass the call to the business object which then uses the DAO to access the DB.
I would not have that try/catch stuff in your DAO either. The best way to notify calling code that something went wrong is for an exception to be thrown. Then the calling code can decide what to do with it (whether to deal with it some way, ignore it, or re-bubble it to the sitewide error handling).

Answer 2

I suggest looking at ColdSpring and its ability to create remote proxies and its ability to secure them using AOP. This is a great way to expose only certain parts of a CFC to remote access and to control by whom they are accessed.
Both topics are covered in the ColdSpring Quick Start guide: http://www.coldspringframework.org/coldspring/examples/quickstart/
I also did a presentation on how to do this. You can see a recording here: http://textiles.online.ncsu.edu/online/Viewer/?peid=a4227aeb1ad84fa89eeb3817f075af5b1d