ColdFusion Application.cfc - order of execution

问题:

I need a reality check - and hopefully an explanation (if my reality is wrong).

The way the CF application framework evaluates things is this (my understanding) - request is passed to cfserver

• cf finds an application.cfm or cfc (based on traversing rules)

• application.cfc executes (if found)

• the THIS scope is set (a series of application specific vars can be set here but

some are required - such as "applicationTimeout" - then a series of events takes place -and methods fired if needed.

-- onApplicationStart()

----onSessionStart()

------onRequestStart()

etc.

so my questions

1) The THIS settings happens on EVERY page request - before anything else?

2) If I set an application variable, in onApplicationStart() - it is available in any process that happens after that - AND should persist in memory for the length of applicationTimeout() - correct?

3) so if I do something like this...

if ( isdefined("application.myvar" ) { this.something = application.myvar; }

it SHOULD work on any page request after the initial request that started the application scope.

however it doesn't appear to do so.

my reason for asking is this - there are some interesting application lever settings that need to be set in the THIS scope... a few of them could be 'intensive' (at least form the perspective of executing on EVERY request - so I want to do them only ONCE, set a structure in persistent mem, and then have those available as THIS.

am I making some wrong assumptions?

thx

回答1:

The ColdFusion Application.cfc documentation has this tidbit of knowledge:

When a request executes, ColdFusion runs the CFC methods in the following order:

1. onApplicationStart (if not run before for this application)
2. onSessionStart (if not run before for this session)
3. onRequestStart
4. onRequest/onCFCRequest
5. onRequestEnd

The onApplicationEnd, onSessionEnd, and onError CFCs are triggered by specific events.

The overall request order has (at least) two more steps.

0: execute all code in cfcomponent that isn't in a cffunction
0.5: run the equivalent of the cfapplication tag for creating the Application

As such the answers to your questions are:

1. If you're setting those variables in step 0, then yes.
2. Correct.
3. That depends on where you're setting the variable. If the values that you are trying to change are listed on the Application variables documentation page for Application.cfc then they must be in step 0. Setting them elsewhere will update the this scope, but will not take effect in step 0.5.

回答2:

There's two things at play here: when code runs, and when variable scopes are availed and how long they last.

• The code outwith any method (ie: the "pseudoconstructor") runs every request. Obviously minimise the amount of code in this part of the CFC.
• Code in various event handlers run as indicated by the event handler name, eg: onApplicationStart() code runs only once, when the application starts. Ditto onSessionStart() only runs once per new session.

Scopes:

• this scope is available throughout the CFC. Behaves exactly like the this-scope in any other CFC, except some this-scoped variables have special meaning (like this.name, this.datasource, etc). Those special-meaning variables can be changed per session or per request in the relevant handlers, but seem to apply to the entire system (ie: not for the specific session or request making the setting change). In normal CFCs, the this scope is used to expose public variables, but as there is no public instance of Application.cfc, there is no point using the this scope beyond making those special settings. If one wants to have variables available to all methods within the CFC, use the variables scope as one normally would. Contrary to someone's advice here, this-scoped variables are NOT the same as application-scoped variables.
• The request scope is also available throughout the CFC (pseudo constructor and methods). These will also be available to the calling code of templates called later in the request, like any other request-scoped variables.
• Application scope: not available in the pseudo-constructor, even after the this.name setting is made. Only becomes available in onApplicationStart() and thenceforth from there.
  • Session scope: similarly, not available in the pseudo-constructor or onApplicationStart()l and not until onSessionStart().

I've demonstrated this in a blog post (test code provided), over here. it's too lengthy to include here, but the stuff above summarises it.

回答3:

Please see the comments as it would appear the below post works but it does not. If you dump the this scope, your new value is displayed, but it does not actually change any application settings.

You can change any of the application settings anywhere you like; however, because the pseudo constructor runs each time a page is requested you will need to constantly change the setting after the pseudo constructor runs. The application scope is not available in the pseudo constructor so you can do this in the onRequestStart or onRequest function. I have done a simple test reassigning the customtagpaths per a condition in the onRequestStart function. You will notice the first time you access the page the custom tags folder will be 'customtags' additional requests will indicate 'someOtherCustomtagsFolder' On a side note if your application settings change on a per-user basis your global application settings will be flip-flopping and could cause problems with other users getting incorrect settings.

<cfcomponent>
<!--- pseudo constructor --->
<cfset this.customtagpaths = expandPath('./customtags')>

<!--- onRequestStart --->
<cffunction name = "onRequestStart" returnType="void">
     <cfif structKeyExists(application,'testSetting')>
          <cfset this.customtagpaths = expandPath('./someOtherCustomtagsFolder')>
     </cfif>
</cffunction>

<!--- onRequest --->
<cffunction name = "onRequest" returntype="void">
     <cfargument name="targetPage" type="String" required = "true" />
     <cfdump var = "#this#" label = "this">
     <cfset application.testSetting = "foo">
     <cfinclude template="#Arguments.targetPage#">
</cffunction>
</cfcomponent>

回答4:

Anything in the this scope inside an Application.cfc file becomes an application varialbe and is only created ONCE per application life cycle. After the application starts, there is no other user for this within Application.cfc.

The first time a CF application is run, the contents of onApplicationStart() are run before onRequest/Start/End (with the exception of the "new in CF10" onServerStart()).

Any application variables set anywhere in the application exist until the application is stopped.

Your code from #3 should just be

if ( !structKeyExists( application, "myvar" ) { application.myvar = foo; }

then reference application.myvar wherever you need it.

From your description, nothing needs to be added to the this scope, it just needs to be put in the application scope.

回答5:

the application scope is not available in the Application.cfc pseudo constructor, because until this.name has been set there is no way to tie the request to the application.

If you are worried about the overhead of creating your apps mappings, one approach would be to cache them in the server scope which is available.

if(!structkeyexists(server, 'myappmappings')){ server.myappmappings = createMappings(); } this.mappings = server.myappmappings;

you might also be able to use cachePut/cache Get to store the mappings in ehcache, but I've not tried that in the pseudo constructor.