Working With Event Handlers

Last updated 8 months ago

Event handlers are the controller layer in ColdBox and is what you will be executing via the URLor a FORMpost. All event handlers are singletons, which means they are cached for the duration of the application, so always remember to var scope your variables in your functions.

Tip: For development we highly encourage you to turn handler caching off or you will have to reinit the application in every request, which is annoying. Open the config/ColdBox.cfc and look for the coldbox.handlerCaching setting.

Once you started the server in the previous section and opened the browser, the default event got executed which maps to an event handler CFC (controller) handlers/main.cfc and the method/action in that CFC called index(). Go open the handlers/main.cfc and let's explore the code.

Handler Code

// Default Action
function index( event, rc, prc ){
prc.welcomeMessage = "Welcome to ColdBox!";
event.setView( "main/index" );
}

Every action in ColdBox receives three arguments:

  • event - An object that models and is used to work with the current request

  • rc - A struct that contains both URL/FORM variables (unsafe data)

  • prc - A secondary struct that is private only settable from within your application (safe data)

This line event.setView( "main/index" ) told ColdBox to render a view back to the user found in views/main/index.cfm using a default layout, which by convention is called Main.cfm which can be found in the layouts folder.

Executing Events

We have now seen how to add handlers via CommandBox using the coldbox create handler command and also execute them by convention by leveraging the following URL pattern:

http://localhost:{port}/folder/handler/action
http://localhost:{port}/handler/action
http://localhost:{port}/handler

Also remember, that if no action is defined in the incoming URL then the default action of index will be used.

Remember that the URL mappings support in ColdBox is what allows you to execute events in such a way from the URL. These are controlled by your application router: config/Router.cfc

Working With Incoming Data

Now, let's open the handler we created before called handlers/hello.cfc and add some public and private variables to it so our views can render the variables.

function index( event, rc, prc ){
// param an incoming variable.
event.paramValue( "name", "nobody" );
// set a private variable
prc.when = dateFormat( now(), "full" );
// set the view to render
event.setView( "hello/index" );
}

Let's open the view now: views/hello/index.cfm and change it to this:

<cfoutput>
<p>Hello #encodeForHTML( rc.name )#, today is #prc.when#</p>
</cfoutput>

Please note that we used the ColdFusion function encodeForHTML() (https://www.cfdocs.org/encodeforhtml) on the public variable. Why? Because you can never trust the client and what they send, make sure you use the built-in ColdFusion encoding functions in order to avoid XSS hacks or worse on incoming public (rc) variables.

If you execute the event now: http://localhost:{port}/hello/index you will see a message of Hello nobody.

Now change the incoming URL to this: http://localhost:{port}/hello/index?name=ColdBox and you will see a message of Hello ColdBox.

Tip: Please see the layouts and views section for in-depth information about them.