Scamper

Scamper is the HTTP library for Scala. It defines the API for reading and writing HTTP messages, and it includes client and server implementations.

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Table of Contents

Getting Started

To use Scamper, start by adding it as a dependency to your project:

libraryDependencies += "com.github.losizm" %% "scamper" % "10.2.1"

HTTP Messages

At the core of Scamper is HttpMessage, which is a trait that defines the fundamental characteristics of an HTTP message. HttpRequest and HttpResponse extend the specification to define characteristics specific to their respective message types.

Building Requests

An HttpRequest can be created using one of the factory methods defined in its companion object. Or you can start with a RequestMethod and use builder methods to further define the request.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.headers.{ Accept, Host}
import scamper.types.Implicits.stringToMediaRange

val req = GET("/motd")
  .withHost("localhost:8080")
  .withAccept("text/plain", "*/*; q=0.5")

Building Responses

An HttpResponse can be created using one of the factory methods defined in its companion object. Or you can start with a ResponseStatus and use builder methods to further define the response.

import scamper.Implicits.stringToEntity
import scamper.ResponseStatus.Registry.Ok
import scamper.headers.{ Connection, ContentType }
import scamper.types.Implicits.stringToMediaType

val res = Ok("There is an answer.")
  .withContentType("text/plain")
  .withConnection("close")

Specialized Header Access

There is a set of methods in HttpMessage that provides generalized header access. With these methods, the header field name is a String, which is case-insensitive, and the header value is a String.

import scamper.Implicits.{ stringToUri, tupleToHeader }
import scamper.RequestMethod.Registry.POST

val req = POST("/api/users").withHeader("Content-Type" -> "application/json")

val contentType: Option[String] = req.getHeaderValue("Content-Type")

This gets the job done in many cases; however, HttpMessage can be extended for specialized header access. There are extension methods provided by the many type classes defined in scamper.headers.

For example, ContentType adds the following methods:

/** Gets Content-Type header value. */
def contentType: MediaType

/** Gets Content-Type header value if present. */
def getContentType: Option[MediaType]

/** Tests whether Content-Type header is present. */
def hasContentType: Boolean

/** Creates message with Content-Type header set to supplied value. */
def withContentType(value: MediaType): HttpMessage

/** Creates message removing Content-Type header. */
def removeContentType(): HttpMessage

So you can work with the header in a type-safe manner.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.POST
import scamper.headers.ContentType
import scamper.types.MediaType

val req = POST("/api/users").withContentType(MediaType("application", "json"))
println(req.contentType.mainType) // application
println(req.contentType.subtype) // json

And with utilities defined in scamper.types.Implicits, you can implicitly convert to specialized header types.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.POST
import scamper.headers.ContentType
import scamper.types.Implicits.stringToMediaType

val req = POST("/api/users").withContentType("application/json")
println(req.contentType.mainType) // application
println(req.contentType.subtype) // json

Specialized Cookie Access

In much the same way specialized access to headers is available, so too is the case for cookies. Specialized access is provided by classes in scamper.cookies.

Request Cookies

In HttpRequest, cookies are stringed together in the Cookie header. You may access the cookies in their unbaked form using generalized header access. Or you can access them using the extension methods provided by RequestCookies, with each cookie represented as PlainCookie.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.cookies.{ PlainCookie, RequestCookies }

val req = GET("https://localhost:8080/motd").withCookies(
  PlainCookie("ID", "bG9zCg"), PlainCookie("Region", "SE-US")
)

// Print name and value of both cookies
req.cookies.foreach(cookie => println(s"${cookie.name}=${cookie.value}"))

// Get cookies by name
val id: Option[PlainCookie] = req.getCookie("ID")
val region: Option[PlainCookie] = req.getCookie("Region")

// Get cookie values by name
assert(req.getCookieValue("ID").contains("bG9zCg"))
assert(req.getCookieValue("Region").contains("SE-US"))

// Get unbaked cookies
assert(req.getHeaderValue("Cookie").contains("ID=bG9zCg; Region=SE-US"))

Response Cookies

In HttpResponse, the cookies are a collection of Set-Cookie header values. Specialized access is provided by ResponseCookies, with each cookie represented as SetCookie.

Along with name and value, SetCookie provides additional attributes, such as the path to which the cookie is valid, when the cookie expires, whether the cookie should be sent over secure channels only, and a few others.

import scamper.Implicits.stringToEntity
import scamper.ResponseStatus.Registry.Ok
import scamper.cookies.{ ResponseCookies, SetCookie }

val res = Ok("There is an answer.").withCookies(
  SetCookie("ID", "bG9zCg", path = Some("/motd"), secure = true),
  SetCookie("Region", "SE-US")
)

// Print both cookies
res.cookies.foreach(println)

// Get cookies by name
val id: Option[SetCookie] = res.getCookie("ID")
val region: Option[SetCookie] = res.getCookie("Region")

// Get attributes of ID cookie
val path: String = id.flatMap(_.path).getOrElse("/")
val secure: Boolean = id.map(_.secure).getOrElse(false)

// Get cookie values by name
assert(res.getCookieValue("ID").contains("bG9zCg"))
assert(res.getCookieValue("Region").contains("SE-US"))

// Get unbaked cookies
assert(res.getHeaderValue("Set-Cookie").contains("ID=bG9zCg; Path=/motd; Secure"))
assert(res.getHeaderValues("Set-Cookie").size == 2)

Note: Each response cookie is presented in its own Set-Cookie header. getHeaderValues() collects all header values into Seq[String]; whereas, getHeaderValue() retrieves first header value only.

Message Body

The message body is represented as Entity, which provides access to a java.io.InputStream.

Creating Body

When building a message, use the Entity factory to create the body. For example, you can create a message with text content.

import scamper.Entity
import scamper.ResponseStatus.Registry.Ok
import scamper.headers.ContentType
import scamper.types.Implicits.stringToMediaType

val body = Entity.fromText("""
<!DOCTYPE html>
<html>
  <head>
    <title>Example</title>
  </head>
  <body>
    <p>Hello, world!</p>
  </body>
</html>
""")
val res = Ok(body).withContentType("text/html; charset=utf-8")

Or create a message using file content.

import java.io.File
import scamper.Entity
import scamper.ResponseStatus.Registry.Ok
import scamper.headers.ContentType
import scamper.types.Implicits.stringToMediaType

val body = Entity.fromFile(new File("./index.html"))
val res = Ok(body).withContentType("text/html; charset=utf-8")

There are implicit converters available for common entity types, so you aren't required to create them explicitly.

import java.io.File
import scamper.Implicits.fileToEntity
import scamper.ResponseStatus.Registry.Ok
import scamper.headers.ContentType
import scamper.types.Implicits.stringToMediaType

val res = Ok(new File("./index.html")).withContentType("text/html; charset=utf-8")

Parsing Body

When handling an incoming message, use an appropriate BodyParser to parse the message body. There is a set of standard parsers available in BodyParsers, such as one used for parsing text content.

import scamper.{ BodyParsers, HttpMessage }

// Create text body parser
implicit val parser = BodyParsers.text(maxLength = 1024)

def printText(message: HttpMessage): Unit = {
  // Parse message body to String using implicit parser
  val text = message.as[String]

  println(text)
}

And you can implement your own parser. Here's one that employs the power of little-json:

import javax.json.{ JsonObject, JsonValue }
import little.json.{ Json, JsonInput }
import little.json.Implicits._
import scamper.{ BodyParser, HttpMessage }

case class User(id: Int, name: String)

implicit object UserBodyParser extends BodyParser[User] {
  // Define how to convert JsonObject to User
  implicit val userInput: JsonInput[User] = {
    case json: JsonObject => User(json.getInt("id"), json.getString("name"))
    case json: JsonValue  => throw new IllegalArgumentException("Not an OBJECT")
  }

  // Parses JSON message body to User
  def parse(message: HttpMessage): User =
    Json.parse(message.body.getInputStream).as[User]
}

def printUser(message: HttpMessage): Unit = {
  // Parse message body to User using UserBodyParser implicitly
  val user = message.as[User]

  println(s"uid=${user.id}(${user.name})")
}

Multipart Message Body

You can create a message with multipart form-data, which is generally required for form submission containing file content. When the multipart body is added to the message, the Content-Type header is set to multipart/form-data with a boundary parameter whose value is used to delimit parts in the encoded body.

import java.io.File
import scamper.{ Multipart, TextPart, FilePart }
import scamper.Implicits.{ HttpMessageType, stringToUri }
import scamper.RequestMethod.Registry.POST

// Build multipart form-data with text and file content
val formData = Multipart(
  TextPart("title", "Form Of Intellect"),
  TextPart("artist", "Gang Starr"),
  TextPart("album", "Step In The Arena"),
  FilePart("track", new File("/music/gangstarr/form_of_intellect.m4a"))
)

// Create request with multipart body
val req = POST("https://upload.musiclibrary.com/songs").withMultipartBody(formData)

And for an incoming message with multipart form-data, there's a standard BodyParser for parsing the message content.

import scamper.{ BodyParsers, HttpRequest, Multipart }

def saveTrack(req: HttpRequest): Unit = {
  // Get parser for multipart message body
  implicit val parser = BodyParsers.multipart()

  // Parse message to Multipart instance
  val multipart = req.as[Multipart]

  // Extracts content from the parts
  val title = multipart.getText("title")
  val artist = multipart.getText("artist")
  val album = multipart.getText("album")
  val track = multipart.getFile("track")

  ...
}

Message Attributes

Attributes are arbitrary key-value pairs associated with a message.

import scala.concurrent.duration.{ Deadline, DurationInt }
import scamper.Implicits.stringToUri
import scamper.{ HttpRequest, HttpResponse }
import scamper.RequestMethod.Registry.GET

def send(req: HttpRequest): HttpResponse = ???

val req = GET("/motd").withAttribute("send-before" -> (Deadline.now + 1.minute))

val res = req.getAttribute[Deadline]("send-before")
  .filter(_.hasTimeLeft)
  .map(_ => send(req))

Note attributes are not included in the transmitted message.

HTTP Authentication

Scamper includes a separate package (i.e., scamper.auth) for working with authentication types and headers.

Challenges and Credentials

When working with authentication, a Challenge is presented in the response, and Credentials in the request. Each of these has an assigned scheme, which is associated with either a token or a set of parameters.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.ResponseStatus.Registry.Unauthorized
import scamper.auth.{ Authorization, Challenge, Credentials, WwwAuthenticate }

// Present response challenge (scheme and parameters)
val challenge = Challenge("Bearer", "realm" -> "developer")
val res = Unauthorized().withWwwAuthenticate(challenge)

// Present request credentials (scheme and token)
val credentials = Credentials("Bearer", "QWxsIEFjY2VzcyEhIQo=")
val req = GET("/dev/projects").withAuthorization(credentials)

Note: The Authorization and WwwAuthenticate header classes are for authentication between user agent and origin server. There are other header classes available for proxy authentication – see scaladoc for details.

Basic Authentication

There are subclasses defined for Basic authentication: BasicChallenge and BasicCredentials.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.ResponseStatus.Registry.Unauthorized
import scamper.auth.{ Authorization, BasicChallenge, BasicCredentials, WwwAuthenticate }

// Provide realm and optional parameters
val challenge = BasicChallenge("admin", "title" -> "Admin Console")
val res = Unauthorized().withWwwAuthenticate(challenge)

// Provide user and password
val credentials = BasicCredentials("sa", "l3tm31n")
val req = GET("/admin/users").withAuthorization(credentials)

In addition, there are methods for Basic authentication defined in the header classes.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.ResponseStatus.Registry.Unauthorized
import scamper.auth.{ Authorization, WwwAuthenticate }

// Provide realm and optional parameters
val res = Unauthorized().withBasic("admin", "title" -> "Admin Console")

// Access basic auth in response
printf(s"Realm: %s%n", res.basic.realm)
printf(s"Title: %s%n", res.basic.params("title"))

// Provide user and password
val req = GET("/admin/users").withBasic("sa", "l3tm3m1n")

// Access basic auth in request
printf(s"User: %s%n", req.basic.user)
printf(s"Password: %s%n", req.basic.password)

Bearer Authentication

There are subclasses defined for Bearer authentication: BearerChallenge and BearerCredentials. And, similar to Basic, there are Bearer-specific methods available in the header classes.

import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.ResponseStatus.Registry.Unauthorized
import scamper.auth.{ Authorization, WwwAuthenticate }

// Provide challenge parameters
val res = Unauthorized().withBearer(
  "scope" -> "user profile",
  "error" -> "invalid_token",
  "error_description" -> "Expired access token"
)

// Print optional realm parameter
res.bearer.realm.foreach(println)

// Print scope from space-delimited parameter
val scope: Seq[String] = res.bearer.scope
scope.foreach(println)

// Print error parameters
res.bearer.error.foreach(println)
res.bearer.errorDescription.foreach(println)
res.bearer.errorUri.foreach(println)

// Test for error conditions
println(res.bearer.isInvalidToken)
println(res.bearer.isInvalidRequest)
println(res.bearer.isInsufficientScope)

// Create request with Bearer token
val req = GET("/users").withBearer("R290IDUgb24gaXQhCg==")

// Access bearer auth in request
printf("Token: %s%n", req.bearer.token)

HTTP Client

Scamper includes HttpClient, which is used for sending requests and handling the responses.

Here we create a POST request and send it over HTTPS. The response handler prints a message based on the response status using the filters defined in ResponseFilter. Also note the request must be created with an absolute URI to make effective use of the client.

import scamper.Implicits.{ stringToEntity, stringToUri }
import scamper.RequestMethod.Registry.POST
import scamper.client.HttpClient
import scamper.client.ResponseFilter._
import scamper.headers.{ ContentType, Location }
import scamper.types.Implicits.stringToMediaType

val req = POST("https://localhost:8080/users")
  .withContentType("application/json")
  .withBody(s"""{ "id": 500, "name": "guest" }""")

HttpClient.send(req) {
  case Successful(_)    => println("Successful")
  case Redirection(res) => println(s"Redirection: ${res.location}")
  case ClientError(res) => println(s"Client error: ${res.status}")
  case ServerError(res) => println(s"Server error: ${res.status}")
  case Informational(_) => println("Informational")
}

HttpClient.send() returns the value returned by the response handler. So you can process the response and return whatever value warranted.

import scamper.BodyParsers
import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.client.HttpClient

implicit val parser = BodyParsers.text()

def getMessageOfTheDay(): Either[Int, String] = {
  val req = GET("http://localhost:8080/motd")

  HttpClient.send(req) { res =>
    res.status.isSuccessful match {
      case true  => Right(res.as[String])
      case false => Left(res.status.code)
    }
  }
}

Creating Client

The examples in the previous section use the HttpClient object as the client. Behind the scenes, this actually creates an instance of HttpClient for one-time usage.

If you plan to send multiple requests, you can create and maintain a reference to an instance, and use it as the client. With that, you also get access to methods corresponding to the standard HTTP request methods.

import scamper.BodyParsers
import scamper.Implicits.stringToUri
import scamper.client.HttpClient

implicit val parser = BodyParsers.text()

// Create HttpClient instance
val client = HttpClient(bufferSize = 4096, readTimeout = 3000)

def getMessageOfTheDay(): Either[Int, String] = {
  // Use client instance
  client.get("http://localhost:8080/motd") { res =>
    res.status.isSuccessful match {
      case true  => Right(res.as[String])
      case false => Left(res.status.code)
    }
  }
}

And if the client is declared as an implicit value, you can make use of send() on the request itself.

import scamper.BodyParsers
import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.GET
import scamper.client.HttpClient
import scamper.client.Implicits.ClientHttpRequestType // Adds send method to request
import scamper.headers.{ Accept, AcceptLanguage }
import scamper.types.Implicits.{ stringToMediaRange, stringToLanguageRange }

implicit val client = HttpClient(bufferSize = 8192, readTimeout = 1000)
implicit val parser = BodyParsers.text(4096)

GET("http://localhost:8080/motd")
  .withAccept("text/plain")
  .withAcceptLanguage("en-US; q=0.6", "fr-CA; q=0.4")
  .send(res => println(res.as[String])) // Send request and print response

Providing Truststore and Trust Manager

When creating a client, you can supply the truststore used for all requests made via HTTPS.

import java.io.File
import scamper.Implicits.{ stringToEntity, stringToUri }
import scamper.client.HttpClient

// Create client that will use supplied truststore
val client = HttpClient(trustStore = Some(new File("/path/to/truststore")))

client.post("https://localhost:3000/messages", body = "Hello there!") { res =>
  if (!res.status.isSuccessful)
    throw new Exception(s"Message not posted: ${res.status.code}")
}

Or, if greater control is required for verifying SSL connections, you may instead provide a trust manager.

import javax.net.ssl.TrustManager
import scamper.Implicits.stringToUri
import scamper.client.HttpClient

class SingleSiteTrustManager(address: String) extends TrustManager {
  ???
}

// Create client that trusts connections to given IP address
val client = HttpClient(trustManager = Some(new SingleSiteTrustManager("192.168.0.2")))

client.get("https://192.168.0.2:3000/messages") { res =>
  ???
}

HTTP Server

Scamper includes an extensible server framework. To demonstrate, let's begin with a simple example.

import scamper.Implicits.stringToEntity
import scamper.ResponseStatus.Registry.Ok
import scamper.server.HttpServer

val server = HttpServer.create(8080) { req =>
  Ok("Hello, world!")
}

This is as bare-bones as it gets. We create a server at port 8080, and, on each incoming request, we send a Hello World message back to the client. Although trite, it demonstrates how easy it is to get going.

We'll use the remainder of this documentation to describe what goes into creating more practical applications.

Server Application

To build a server, you begin with ServerApplication. This is a mutable structure to which you apply changes to configure the server. Once the desired settings are applied, you invoke one of several methods to create the server.

You can obtain an instance of ServerApplication from the HttpServer object.

val app = HttpServer.app()

This gives you the default application as a starting point. With this in hand, you can set the location of the server log.

app.logger(new File("/tmp/server.log"))

And there are performance-related settings that can be tweaked as well.

app.backlogSize(50)
app.poolSize(10)
app.queueSize(25)
app.bufferSize(8192)
app.readTimeout(3000)
app.headerLimit(100)
app.keepAlive(5, 10)

The backlogSize specifies the maximum number of incoming connections that can wait before being accepted. Incoming connections that exceed this limit are refused.

The poolSize specifies the maximum number of requests processed concurrently.

The queueSize specifies the maximum number of requests permitted to wait for processing. Incoming requests that exceed this limit are sent 503 Service Unavailable.

The bufferSize is the length in bytes of the buffer used when reading from and writing to a socket.

The readTimeout controls how long a read from a socket blocks before it times out, whereafter 408 Request Timeout is sent to client.

The headerLimit sets the maximum number of request headers allowed. Incoming requests that exceed this limit are sent 431 Request Header Fields Too Large.

The keepAlive settings enable keep-alive connections using the specified timeout (in seconds) and max requests per connection.

Request Handlers

You define application-specific logic in instances of RequestHandler and add them to the application. The request handler accepts an HttpRequest and returns either an HttpRequest or an HttpResponse. If the handler does not satisfy the request, it returns an HttpRequest so that the next handler has its turn. Otherwise, it returns an HttpResponse, and any remaining handlers are effectively ignored.

import scamper.RequestMethod.Registry.{ GET, HEAD }
import scamper.ResponseStatus.Registry.MethodNotAllowed
import scamper.headers.Allow

// Add handler to log request line and headers to stdout
app.incoming { req =>
  println(req.startLine)
  req.headers.foreach(println)
  println()
  req // Return request for next handler
}

// Add handler to allow GET and HEAD requests only
app.incoming { req =>
  (req.method == GET || req.method == HEAD) match {
    // Return request for next handler
    case true  => req
    // Otherwise return response to end request chain
    case false => MethodNotAllowed().withAllow(GET, HEAD)
  }
}

Note the order in which handlers are applied matters. For instance, in the example above, you'd swap the order of handlers if you wanted to log GET and HEAD requests only, which means all other requests would immediately be sent 405 Method Not Allowed and never make it to the request logger.

Also note a request handler is not restricted to returning the same request it accepted.

import scamper.BodyParser
import scamper.Implicits.stringToEntity
import scamper.RequestMethod.Registry.POST
import scamper.headers.ContentLanguage
import scamper.types.LanguageTag
import scamper.types.Implicits.stringToLanguageTag

// Translates message body from French (Oui, oui.)
app.incoming { req =>
  val translator: BodyParser[String] = ???

  (req.method == POST && req.contentLanguage.contains("fr")) match {
    case true  => req.withBody(translator.parse(req)).withContentLanguage("en")
    case false => req
  }
}

Targeted Handling

A handler can be added to a targeted path with or without a targeted request method.

import scamper.Implicits.stringToEntity
import scamper.RequestMethod.Registry.GET
import scamper.ResponseStatus.Registry.{ Forbidden, Ok }

// Match request method and exact path
app.incoming(GET, "/about") { req =>
  Ok("This server is powered by Scamper.")
}

// Match exact path and any method
app.incoming("/private") { req =>
  Forbidden()
}

And handlers can be added using methods corresponding to the standard HTTP request methods.

import scamper.BodyParsers
import scamper.Implicits.stringToUri
import scamper.ResponseStatus.Registry.{ Created, Ok }
import scamper.headers.Location

// Match GET requests to given path
app.get("/about") { req =>
  Ok("This server is powered by Scamper.")
}

// Match POST requests to given path
app.post("/messages") { req =>
  def post(message: String): Int = ???

  implicit val parser = BodyParsers.text()

  val id = post(req.as[String])
  Created().withLocation(s"/messages/$id")
}

Path Parameters

Parameters can be specified in the path and their resolved values made available to the handler. When a parameter is specified as :param, it matches a single path segment; whereas, *param matches the path segment along with any remaining segments, including intervening path separators (i.e., /).

import scamper.Implicits.fileToEntity
import scamper.ResponseStatus.Registry.{ Accepted, NotFound, Ok }
import scamper.server.Implicits.ServerHttpRequestType

// Match request method and parameterized path
app.delete("/orders/:id") { req =>
  def deleteOrder(id: Int): Boolean = ???

  // Get resolved parameter
  val id = req.params.getInt("id")

  if (deleteOrder(id))
    Accepted()
  else
    NotFound()
}

// Match prefixed path with any request method
app.get("/archive/*path") { req =>
  def findFile(path: String): Option[File] = ???

  // Get resolved parameter
  val path = req.params.getString("path")

  findFile(path).map(Ok(_)).getOrElse(NotFound())
}

Note there can be at most one *param, which must be specified as the the last segment in the path; however, there can be multiple :param instances specified.

import scamper.BodyParser
import scamper.Implicits.stringToEntity
import scamper.ResponseStatus.Registry.Ok
import scamper.server.Implicits.ServerHttpRequestType

// Match path with two parameters
app.post("/translate/:in/to/:out") { req =>
  def translator(from: String, to: String): BodyParser[String] = ???

  val from = req.params.getString("in")
  val to = req.params.getString("out")

  Ok(translator(from, to).parse(req))
}

Serving Static Files

You can add a request handler at a mount path to serve static files from a source directory.

app.files("/app/main", new File("/path/to/public"))

This adds a handler to serve files from the directory at /path/to/public. The files are mapped based on the request path excluding the mount path. For example, http://localhost:8080/app/main/images/logo.png would map to /path/to/public/images/logo.png.

Serving Static Resources

If your web assets are bundled in a jar file, just drop the jar on the classpath, and you can configure the application to serve its contents.

app.resources("/app/main", "assets")

In the above configuration, requests prefixed with /app/main are served resources from the assets directory. The mapping works similiar to static files, only the resources are located using a class loader. (See ServerApplication.resources() in scaladoc for additional details.)

Aborting Response

At times, you may wish to omit a response for a particular request. On such occassions, you'd throw ResponseAborted from the request handler.

import scamper.headers.Referer
import scamper.server.ResponseAborted

// Ignore requests originating from evil site
app.incoming { req =>
  if (req.referer.getHost == "www.phishing.com")
    throw ResponseAborted("Not trusted")
  req
}

Error Handler

You can define an ErrorHandler to handle exceptions thrown from your request handlers.

import scamper.ResponseStatus.Registry.{ BadRequest, InternalServerError }

// Accepts `Throwable` and `HttpRequest`; returns `HttpResponse`
app.error { (err, req) =>
  def isClientError(err: Throwable): Boolean = ???

  isClientError(err) match {
    case true  => BadRequest("Your bad.")
    case false => InternalServerError("My bad.")
  }
}

Router

Use Router to structure the application routes hierarchically. Router works in much the same way as ServerApplication, except it is configured for request handling only, and all router paths are relative to its mount path.

import scamper.Implicits.stringToEntity
import scamper.ResponseStatus.Registry.{ NotFound, Ok }
import scamper.server.HttpServer
import scamper.server.Implicits.ServerHttpRequestType

val app = HttpServer.app()

// Mount path of router is /api
app.use("/api") { router =>
  val messages = Map(1 -> "Hello, world!", 2 -> "Goodbye, cruel world!")

  // Will be mapped to /api/messages
  router.get("/messages") { req =>
    Ok(messages.mkString("\r\n"))
  }

  // Will be mapped to /api/messages/:id
  router.get("/messages/:id") { req =>
    val id = req.params.getInt("id")
    messages.get(id)
     .map(Ok(_))
     .getOrElse(NotFound())
  }
}

Response Filters

Response filtering is performed by adding instances of ResponseFilter to the application. They are applied, in order, after one of the request handlers generates a response.

app.outgoing { res =>
  println(res.startLine)
  res.headers.foreach(println)
  println()
  res // Return response for next filter
}

This is pretty much the same as the request logger from earlier, only instead of HttpRequest, it accepts and returns HttpResponse.

And the filter is not restricted to returning the same response it accepts.

import scamper.server.Implicits.ServerHttpResponseType

// Gzip response body if not empty
app.outgoing { res =>
  res.body.isKnownEmpty match {
    case true  => res
    case false => res.withGzipContentEncoding()
  }
}

Securing Server

The last piece of configuration is whether to secure the server using SSL/TLS. To use a secure transport, you must supply an appropriate key and certificate.

app.secure(new File("/path/to/private.key"), new File("/path/to/public.cert"))

Or, if you have them tucked away in a keystore, you can supply the keystore location.

// Supply location, password, and store type (i.e., JKS, JCEKS, PCKS12)
app.secure(new File("/path/to/keystore"), "s3cr3t", "pkcs12")

Creating Server

When the desired application has been configured, you're ready to create the server.

val server = app.create(8080)

If the server must bind to a particular host, you can provide the host name or IP address.

val server = app.create("192.168.0.2", 8080)

An instance of HttpServer is returned, which can be used to query server details.

printf("Host: %s%n", server.host)
printf("Port: %d%n", server.port)
printf("Secure: %s%n", server.isSecure)
printf("Logger: %s%n", server.logger)
printf("Backlog Size: %d%n", server.backlogSize)
printf("Pool Size: %d%n", server.poolSize)
printf("Queue Size: %d%n", server.queueSize)
printf("Buffer Size: %d%n", server.bufferSize)
printf("Read Timeout: %d%n", server.readTimeout)
printf("Header Limit: %d%n", server.headerLimit)
printf("Keep-Alive: %s%n", server.keepAlive.getOrElse("disabled"))
printf("Closed: %s%n", server.isClosed)

And, ultimately, it is used to gracefully shut down the server.

server.close() // Good-bye, world.

API Documentation

See scaladoc for additional details.

License

Scamper is licensed under the Apache License, Version 2. See LICENSE file for more information.