Question

I have to use a Variable(Query Resultset) in ColdFusion, which will get the results from Other Application DB, and stores in Coldfusion Application.

The main idea is that I need to call the other Application DB only at Server startup time and cache the results in local. And I need to read the variable in other pages in my Application. I won t overwrite that variable in any page.

On googling I found that onApplicationStart is useful to assign the variables at Application Startup time.

Is using the onApplicationStart fine or is there any other way? We can assign a variable at startup time(one time).

If onApplicationStart is fine: how to use? Maybe any link where it is explained clearly is helpful.

Answer 1

Well, it depends. How often will this query data be updated? If it really is unchanging, then onApplicationStart() is a fine place to put it. However, if it will change every so often, you can just tell Coldfusion to cache the query for a certain period of time, then you don t need to mess with onApplicationStart(), but rather when you call the query it will return the cached result automatically (within your specified time period).

Regardless, I would write a custom function to retrieve the data. Then it will be trivial to call it from onApplicationStart() or elsewhere.

Startup.cfc: (Named whatever you like)

<!--- Replace the datasource name with your db name --->
<cffunction name="getStartupQuery" hint="Returns a query recordset for startup">
    <cfargument name="datasource" required="no" type="string" default="OtherAppDB">
    <!--- Init the query variable --->
    <cfset var result = queryNew("id")>

    <!-- Get the query dataset --->
    <cfquery name="result" datasource="#arguments.datasource#">
         YOUR QUERY HERE
    </cfquery>

    <cfreturn result>
</cffunction>

Application.cfc: (Just the important parts)

<cffunction name="onApplicationStart">
    <!--- init the startup.cfc, then retrieve the data
    and save it to the application scope. Remember the component name must match
    your component above --->
    <cfset var startup = createObject("component", "startup")>
    <cfset application.varFromOtherDB = startup.getStartupQuery()>
    <cfreturn true>
</cffunction>

Now, you should be able to access this variable from any CFM or CFC in your application using:

<cfset myNewVar = application.varFromOtherDB>
or
#application.varFromOtherDB#

IF you use the onApplicationStart() method, I highly recommend implementing a method to reinit the application. For an example, see this other discussion.

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