Internal Self Calls

Introduction

Starcounter provides an efficient way for REST communication within the codehost instance. Simply put, Self is used to call handlers that are registered using the Handle class inside the codehost. To communicate between different codehosts, Http should be used. Self communication does not use either networking or shared memory, so it is very efficient. It is represented by the Self class, which is similar to the Http interface. For example, the same HTTP methods are supported, as in Http. However, in comparison, Self calls are always synchronous, so asynchronous mode is not presented in it. Like for Http, the Response object is returned as a result of Self call. To conclude, Self is used ubiquitously in Starcounter as it is the core REST communication mechanism.

Usage

Here are some examples of Self calls:

Response resp = Self.GET("/MyHandler");

Templated Self can be used to specify what object type is expected in Body of the Response and gets it as a return value, for example:

Json json = Self.GET<Json>("/MyApp/MyJsonObject/13235");

Here, an object of type Json is expected to be in the Body.

A specific JSON type can also be used:

Master master = Self.GET<Master>("/emails");

Here is an example of expecting and obtaining the string Body:

String myText = Self.GET<String>("/MyApp/MyTextDocument/54664");

or expecting a binary body:

Byte[] myBinaryData = Self.GET<Byte[]>("/EncodedDocument/34563");

Note that if the actual response Body object returned in handler is of different type than expected - the conversion exception will be thrown.

Getting Current Level in the Call Hierarchy

The hierarchy of Self calls can be quite deep and sometimes its needed to get the current call level. To achieve that there is a special thread static variable Handle.CallLevel. Every Self call the variable is incremented and then restored to current value on the way back.