Sending a custom POST https request in dispatch (+cookies, + headers)

Dispatch is built on top of Async Http Client. Therefore, myRequest in the example:

 val myRequest = url("http://example.com/some/path")

is com.ning.http.client.RequestBuilder.

Calling the POST method on RequestBuilder turns the request into a POST request. That's what's happening in the myPost example:

def myPost = myRequest.POST

I often find the Dispatch documentation difficult to follow. For a quick overview of the all the various Dispatch operators, see: Periodic Table of Dispatch Operators

If you're asking how to build a POST request and add custom form parameters, you probably want to use the <<(values) operator like this:

val params = Map("param1" -> "val1", "param2" -> "val2") 
val req = url("http://www.example.com/some/path" <<(params)

Likewise if you want to add some custom headers you can use the <:<(map) operator like this:

val headers = Map("x-custom1" -> "val1", "x-custom2" -> "val2") 
val req = url("http://www.example.com/some/path" <<(params) <:<(headers)

Update: Actually, there is no POST method on RequestBuilder. The call to POST is part of Dispatch and calls setMethod on the underlying RequestBuilder. See dispatch.MethodVerbs for more details.