megamsys / newman   1.3.12

Apache License 2.0 GitHub

A REST Client Made For Humans

Scala versions: 2.11


Build Status

Newman is StackMob's HTTP client. We named it after the Seinfeld Character.

And wrote a post explaining our motivation for building this library here.

Newman supports the following basic features:

  • Making HTTP requests and receiving responses
  • Serializing and deserializing request and response bodies
  • Serializing and deserializing requests and responses for replay or caching
  • In memory response caching with TTL expiry
  • ETag HTTP caching

Usage for scala 2.11


	resolvers ++= Seq(Resolver.sonatypeRepo("releases"),
	Resolver.bintrayRepo("scalaz", "releases"),
	Resolver.bintrayRepo("megamsys", "scala"))

	libraryDependencies += "io.megam" %% "newman" % "1.3.12"

Basic Usage

import com.stackmob.newman._
import com.stackmob.newman.dsl._
import scala.concurrent._
import scala.concurrent.duration._

implicit val httpClient = new ApacheHttpClient
//execute a GET request
val url = new URL("")
val response = Await.result(GET(url).apply, 1.second) //this will throw if the response doesn't return within 1 second
println(s"Response returned from ${url.toString} with code ${response.code}, body ${response.bodyString}")

#Publishing in bintray

For more information

#from the sbt REPL

> bintrayChangeCredentials

> bintrayWhoami

> publish

#The DSL Newman comes with a DSL which is inspired by Dispatch, but uses mostly english instead of symbols. This DSL is the recommended way to build requests, and the above example in "Basic Usage" uses the DSL to construct a GET request.

To start using the DSL, simply import com.stackmob.newman.dsl._. The functions of interest in the DSL are uppercase representations of the HTTP verbs:

  • def GET(url: URL)(implicit client: HttpClient)
  • def POST(url: URL)(implicit client: HttpClient)
  • def PUT(url: URL)(implicit client: HttpClient)
  • def DELETE(url: URL)(implicit client: HttpClient)
  • def HEAD(url: URL)(implicit client: HttpClient)

Notice that each method takes an implicit HttpClient, so you must declare your own implicit before you use any of the above listed DSL methods, or pass one explicitly.

Each method listed above returns a Builder, which works in concert with the implicit methods defined in the DSL package to let you build up a request and then execute it.

Executing Requests

The most important method on com.stackmob.newman.HttpRequest is def apply: Future[HttpResponse]. A few notes on this method:

  • It returns immediately after the request is started
  • It returns a scala.concurrent.Future that will be complete immediately after the executing request is complete
  • If you want to schedule some action to happen after the response is available, use onComplete or a similar callback
  • The Future can also fail with an exception, which you can react to with onFailure
  • If you need to block your code from proceeding until the HttpResponse is available, use Await.result.
  • We recommend refactoring your blocking code to remove Await.result calls it possible, since latencies are unpredictable, subject to network conditions, etc...


Newman comes with built in support for serializing HttpRequests and HttpResponses to Json.

To serialize either, simply call the toJson(prettyPrint: Boolean = false): String method on the HttpRequest or HttpResponse. And to deserialize, call HttpRequest.fromJson(json: String): Result[HttpRequest] or HttpResponse.fromJson(json: String): Result[HttpResponse] to deserialize the HttpRequest or HttpResponse, respectively.

ETag Support

Newman comes with an implementation of HttpClient called ETagAwareHttpClient. This implementation requires an underlying "raw" HttpClient to execute requests to a server, but it also requires an implementation of HttpResponseCacher.

It uses this HttpResponseCacher to check the cache for a response corresponding to a given request. If it finds one and that response has an ETag header in it, the ETagAwareHttpClient automatically sends an If-None-Match header to the server containing that ETag. In this case, if the server responds with a 304 NOT MODIFIED response code, then ETagAwareHttpClient will return the cached version. In all other cases, ETagAwareHttpClient will cache and return the new response.

Usage With the DSL

Using ETagAwareHttpClient is very similar to the basic usage above. Following demonstrates how to use the client with a (built-in) in-memory cache implementation.

import com.stackmob.newman.{ETagAwareHttpClient, ApacheHttpClient}
import com.stackmob.newman.caching.InMemoryHttpResponseCacher
import com.stackmob.newman.dsl._

//change this implementation to your own if you want to use Memcached, Redis, etc
val cache = new InMemoryHttpResponseCacher
val rawHttpClient = new ApacheHttpClient
//eTagClient will be used in the DSL to construct & execute requests below
implicit val eTagClient = new ETagAwareHttpClient(rawHttpClient, cache)

val url = new URL("")
//since the cacher is empty, this will issue a request to without an If-None-Match header
val res1 = GET(url).apply
//assuming res1 contained an ETag and fully supports ETag headers,
// will return a 304 response code in this request and res2 will come from the cache
val res2 = GET(url).apply