This document provides an overview of Akka HTTP, a library for building HTTP-based services using Scala and Akka. It describes the common abstractions used in Akka HTTP like HTTP requests, responses, entities, and marshalling/unmarshalling. It also explains the low-level and high-level APIs, with the low-level API providing basic request handling functionality and the high-level API using directives and routing DSL for defining routes in a more flexible way.

1. Akka - HTTP
Harshit Daga
Software Consultant
Knoldus Software LLP

2. Agenda
● Overview of Akka Http
● Common Abstractions
● Low level API
● High level API
● Demo

3. Overview of Akka-Http
● A library for providing HTTP based services.
● Used for building REST APIs.
● Build on the top of Akka- actors and Streams.

4. Overview of Akka Http (Cont..)
● Akka Http contains following module:
– Akka-http-core
– Akka-http
– Akka-http-testkit
– Akka-http-spray-json
– Akka-http-xml

5. Overview of Akka-Http (Cont..)

6. Common Abstractions
● HttpRequest
● HttpResponse
● HttpEntity
● HttpHeaders
● Marshalling & Unmarshalling

7. Http Request
● Used to send a request to the server
● Akka-Http request consists of -
– method (GET, POST, etc.)
– A URI
– Seq of headers
– Entity (body data), and
– Protocol
HttpRequest (method, URI, List(headers), entity, protocol)

8. Http Response
● Response is what server replies to its client.
● HttpResponse consists of
– Status code
– Seq of headers
– Entity
– Protocol
HttpResponse(StatusCode, List(headers), entity, protocol)

9. Http Entity
● Contains the data bytes of a message with
content-type and length.
● Different kinds of entities:
– Strict
– Default
– Chunked
– ClosedDelimited
– IndefiniteLength

10. Marshalling
● To convert higher level objects into wire-format.
● Some pre-defined marshallers :
– Array[Byte]
– String
– ByteString
– Array[Char]
– FormData

11. Unmarshalling
● To convert lover level objects into higher level
objects.
● Some pre-defined unmarshallers:
– Byte, Boolean
– Short, Int, Long , Float, Double
– String
– Array[String]

12. Low Level API
● The implementation is in akka-http-core
module.
● It provides support for :
– Connection management
– Parsing and rendering of messages and headers
– Timeout management
– Response ordering

13. Low Level API (Cont...)
Http().bindAndHandleSync(reqHandler, interface, portAddr)
This method specifies the interface and port to bind for
handling incoming Http requests.

14. Low Level API (Cont...)
Low Level API is based simply on mapping from request to response

15. High Level API
● Low level API becomes uneasy to handle when we
need to create large number of routes.
● For this we use should Higher Level APIs.
● Provides a flexible ways to create routes.
● These are located in akka-http module.
● Low level API becomes uneasy to handle when we
need to create large number of routes.
● For this we use should Higher Level APIs.
● Provides a flexible ways to create routes.
● These are located in akka-http module.

16. High Level API (Cont..)
● Directives
● Routing DSL (alternative to Low level API)
● Rejection & Exception Handling
● Path Matcher
● Case class extraction

17. Directives
● A block used for creating route structure.
● Extract the requests from RequestContext to make
it available for inner route.

18. Path Matcher
● When request enters the structure, it has an
unmatched path.
● The path matcher decides on which route it is
supposed to hit.
path(“foo” / “bar”)
means path is foo / bar

19. Case Class extraction
● Used to directly map request to the case class

20. Thank You !!!