Head Rush Ajax

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asynchronous applications

A synchronous test drive

When you run the synchronous version of the coffee maker application,

you should notice quite a big difference. As soon as you click on “Order

Coffee”, you’re stuck. The button stays highlighted, and if you try to

enter another order, you get the spinning beach ball (on Macs) or the

hourglass (on Windows), meaning “You’ll have to wait—I’m busy!”

As soon as you click on “Order

Coffee”, you’re stuck.

Nothing else can happen until the

response comes back from the

server. You won’t even see the

status of the coffee maker change,

because that code can’t run!

If you try to do something else, like

start a new order, you won’t see

anything happen, because everything is

frozen until that response comes back.

You just get your system’s “wait” icon.

The coffee is nished brewing,

the status of the rst coffee

maker is set to “Idle” (because it’s

done brewing again), and you never

actually see the “Brewing” status.

All that work to add another request

object, and now you can’t even use

it. Synchrony sucks when it comes to

coffee makers!

...time passes...