Scamper
Scamper is the HTTP library for Scala. It defines the interface for reading and writing HTTP messages. In addition, it provides client and server implementations, both of which support WebSockets with permessage-deflate.
The client handles content and transfer encoding, as well as manages cookies.
The server is integrated into a lightweight web framework, which allows developers to create web applications as pipelines of request handlers.
Table of Contents
- Getting Started
- HTTP Messages
- Specialized Header Access
- Specialized Cookie Access
- Message Body
- Multipart Message Body
- Message Attributes
- HTTP Authentication
- HTTP Client
- HTTP Server
- API Documentation
- License
Getting Started
To use Scamper, start by adding it as a dependency to your project:
libraryDependencies += "com.github.losizm" %% "scamper" % "21.0.0"
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 a factory method 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")
.setHost("localhost:8080")
.setAccept("text/plain", "*/*; q=0.5")
Building Responses
An HttpResponse
can be created using a factory method 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.")
.setContentType("text/plain")
.setConnection("close")
Specialized Header Access
There is a set of methods in HttpMessage
that provides generalized header access. With these methods, the header 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").setHeaders("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 type classes defined in scamper.headers
.
For example, ContentType
adds the following methods:
/** Tests for Content-Type header. */
def hasContentType: Boolean
/** Gets Content-Type header value. */
def contentType: MediaType
/** Optionally gets Content-Type header value. */
def getContentType: Option[MediaType]
/** Creates message setting Content-Type header. */
def setContentType(value: MediaType): HttpMessage
/** Creates message removing Content-Type header. */
def removeContentType(): HttpMessage
So you can work with the header using specialized header types.
import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.Post
import scamper.headers.ContentType
import scamper.types.MediaType
val req = Post("/api/users").setContentType(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 values to 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").setContentType("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 presented as PlainCookie
.
import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.Get
import scamper.cookies.{ PlainCookie, RequestCookies }
val req = Get("https://localhost:8080/motd").setCookies(
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 presented 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.").setCookies(
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. Whereas getHeaderValue()
retrieves the first header value only, getHeaderValues()
collects all header values into a Seq[String]
.
Message Body
The message body is represented as an Entity
, which provides access to an 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("""
<!DOCTYPE html>
<html>
<head>
<title>Example</title>
</head>
<body>
<p>Hello, world!</p>
</body>
</html>
""")
val res = Ok(body).setContentType("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(new File("./index.html"))
val res = Ok(body).setContentType("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")).setContentType("text/html; charset=utf-8")
Parsing Body
When handling an incoming message, use an appropriate BodyParser
to parse the message body. There are factory methods available, such as one used for creating a text body parser.
import scamper.{ BodyParser, HttpMessage }
// Create text body parser
implicit val parser = BodyParser.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 powered by 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 UserParser 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.inputStream).as[User]
}
def printUser(message: HttpMessage): Unit = {
// Parse message body to User (implicitly using UserParser)
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("media", new File("/music/gang_starr/form_of_intellect.m4a"))
)
// Create request with multipart body
val req = Post("https://upload.musiclibrary.com/songs").setMultipartBody(formData)
And for an incoming message with multipart form-data, there's a standard BodyParser
for parsing the message content.
import scamper.{ BodyParser, HttpRequest, Multipart }
def saveTrack(req: HttpRequest): Unit = {
// Get parser for multipart message body
implicit val parser = BodyParser.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("media")
...
}
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").setAttributes("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 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().setWwwAuthenticate(challenge)
// Present request credentials (scheme and token)
val credentials = Credentials("Bearer", "QWxsIEFjY2VzcyEhIQo=")
val req = Get("/dev/projects").setAuthorization(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().setWwwAuthenticate(challenge)
// Provide user and password
val credentials = BasicCredentials("sa", "l3tm31n")
val req = Get("/admin/users").setAuthorization(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().setBasic("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").setBasic("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
. In addition, 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().setBearer(
"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").setBearer("R290IDUgb24gaXQhCg==")
// Access bearer auth in request
printf("Token: %s%n", req.bearer.token)
HTTP Client
Scamper provides HttpClient
for sending requests and handling the responses.
import scamper.Implicits.{ stringToEntity, stringToUri }
import scamper.RequestMethod.Registry.Post
import scamper.client.HttpClient
import scamper.headers.ContentType
import scamper.types.Implicits.stringToMediaType
val req = Post("https://localhost:8080/users")
.setContentType("application/json")
.setBody(s"""{ "id": 500, "name": "guest" }""")
// Send request and print response status
HttpClient.send(req) { res =>
println(res.status)
}
Note: The outgoing request must be created with an absolute URI to make effective use of the client.
Creating Client
In the previous example, the HttpClient
object is used as the client. Behind the scenes, this creates an HttpClient
instance for one-time usage.
If you plan to send multiple requests, you can create and maintain a reference to a client. With it, you also get access to methods corresponding to standard HTTP request methods.
import scamper.BodyParser
import scamper.Implicits.stringToUri
import scamper.client.HttpClient
implicit val parser = BodyParser.text()
// Create client instance
val client = HttpClient()
def messageOfTheDay: Either[Int, String] =
client.get("http://localhost:8080/motd") {
case res if res.isSuccessful => Right(res.as[String])
case res if !res.isSuccessful => Left(res.statusCode)
}
And, if an implicit client is in scope, you can make use of send()
on the request itself.
import scamper.BodyParser
import scamper.Implicits.stringToUri
import scamper.RequestMethod.Registry.Get
import scamper.client.HttpClient
import scamper.client.Implicits.ClientHttpRequest // Adds send method to request
import scamper.headers.{ Accept, AcceptLanguage }
import scamper.types.Implicits.{ stringToMediaRange, stringToLanguageRange }
implicit val client = HttpClient()
implicit val parser = BodyParser.text(4096)
Get("http://localhost:8080/motd")
.setAccept("text/plain")
.setAcceptLanguage("fr-CA; q=0.6", "en-CA; q=0.4")
.send(res => println(res.as[String])) // Send request and print response
Configuring Client
You can also create a client using ClientSettings
, which allows you to configure the client before creating it.
import java.io.File
import scamper.Implicits.{ stringToEntity, stringToUri }
import scamper.client.HttpClient
import scamper.cookies.CookieStore
import scamper.types.Implicits.{ stringToContentCodingRange, stringToMediaRange }
// Build client from settings
val client = HttpClient
.settings()
.accept("text/plain; q=0.9", "application/json; q=0.1")
.acceptEncoding("gzip", "deflate")
.bufferSize(8192)
.readTimeout(3000)
.continueTimeout(1000)
.cookies(CookieStore())
.trust(new File("/path/to/truststore"))
.create()
client.post("https://localhost:3000/messages", body = "Hello there!") { res =>
assert(res.isSuccessful, s"Message not posted: ${res.statusCode}")
}
The accept
provides a list of accepted media types, which are used to set the Accept header on each outgoing request.
The acceptEncoding
provides a list of accepted content encodings, which are used to set the Accept-Encoding header on each outgoing request.
The bufferSize
is the size in bytes used for the client send and receive buffers.
The readTimeout
sets how many milliseconds a read on the client socket blocks before a SocketTimeoutException
is thrown.
The continueTimeout
specifies how many milliseconds the client waits for a 100 (Continue) response from the server before the client sends the request body. This behavior is effected only if the request includes an Expect header set to 100-Continue.
The cookies
is used to store cookies included in HTTP responses. Using the cookie store, the client automatically adds the appropriate cookies to each outgoing request.
You can supply a truststore using trust
, as demonstrated in the previous example. Or, if greater control is required for securing connections, you can supply a trust manager instead.
import javax.net.ssl.TrustManager
import scamper.Implicits.stringToUri
import scamper.client.HttpClient
class SingleSiteTrustManager(address: String) extends TrustManager {
// Provide TrustManager implementation
???
}
// Build client from settings
val client = HttpClient
.settings()
.readTimeout(5000)
// Use supplied trust manager
.trust(new SingleSiteTrustManager("192.168.0.2"))
.create()
client.get("https://192.168.0.2:3000/messages") { res =>
// Handle response
???
}
Adding Request and Response Filters
To perform common operations on client requests and their responses, you can add filters to the client.
import scamper.Uri
import scamper.client.HttpClient
import scamper.client.Implicits._
import scamper.cookies._
val settings = HttpClient.settings()
settings.readTimeout(30 * 1000)
// Add request filter
settings.outgoing { req =>
def findCookies(target: Uri): Seq[PlainCookie] = ???
// Add cookies to request
req.setCookies { findCookies(req.absoluteTarget) }
}
// Add response filter
settings.incoming { res =>
def storeCookies(target: Uri, cookies: Seq[SetCookie]): Unit = ???
// Store cookies from response
storeCookies(res.absoluteTarget, res.cookies)
res
}
// Create client
val client = settings.create()
You can add multiple request and response filters. If multiple filters are added, each is executed in the order it is added. That is, request filters are executed in order, and response filters are executed in order.
Using WebSocket Client
The client instance can also be used as a WebSocket client.
import scamper.Implicits.stringToUri
import scamper.client.HttpClient
HttpClient().websocket("ws://localhost:9090/hello") { session =>
session.onText { message =>
println(s"Received text message: $message")
if (message.equalsIgnoreCase("bye"))
session.close()
}
session.onPing { data =>
println(s"Received ping message.")
session.pong(data)
}
session.onPong { data =>
println(s"Received pong message.")
}
session.onError { err =>
println(s"Encountered error: $err")
err.printStackTrace()
}
session.onClose { statusCode =>
println(s"WebSocket connection closed: $statusCode")
}
session.idleTimeout(5000)
session.open()
session.send("Hello, server!")
}
In the above example, the client establishes a WebSocket connection to the specified target URI. (Note use of "ws" scheme. For secure connections, use "wss" instead.)
After the client and server perform the opening handshake, a WebSocketSession
is passed to the supplied handler. The handler then applies subsequent handlers for various message types along with an error handler.
It then sets the session's idle timeout. If no messages are received in any 5 second span, the session will be closed automatically.
Before the session begins reading incoming messages, it must first be opened. And, to kick things off, a simple text message is sent to the server.
See WebSocketSession in scaladoc for additional details.
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(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 simple text 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 for acceptance. 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 many milliseconds 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 persistent connections using the specified idle timeout 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.isGet || req.isHead match {
// Return request for next handler
case true => req
// Return response to end request chain
case false => MethodNotAllowed().setAllow(Get, Head)
}
}
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, and all other requests would immediately be sent 405 (Method Not Allowed) and never make it to the request logger.
And a request handler is not restricted to returning the same request it accepted.
import scamper.BodyParser
import scamper.Implicits.stringToEntity
import scamper.headers.ContentLanguage
import scamper.types.LanguageTag
import scamper.types.Implicits.stringToLanguageTag
// Translates message body from French (Oui, oui.)
app.incoming { req =>
implicit val translator: BodyParser[String] = ???
req.isPost && req.contentLanguage.contains("fr") match {
case true => req.setBody(req.as[String]).setContentLanguage("en")
case false => req
}
}
Target Handling
A handler can be added to a target path with or without a target 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("/about", Get) { 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.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 = BodyParser.text()
val id = post(req.as[String])
Created().setLocation(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.ServerHttpRequest
// 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")
deleteOrder(id) match {
case true => Accepted()
case false => NotFound()
}
}
// Match prefixed path for GET requests
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())
}
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.ServerHttpRequest
// Match path with two parameters
app.post("/translate/:in/to/:out") { req =>
def translate(from: String, to: String): BodyParser[String] = ???
val from = req.params.getString("in")
val to = req.params.getString("out")
val result = req.as(translate(from, to))
Ok(result)
}
Serving Static Files
You can mount a file server as a specialized request handler.
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 located using the request path minus 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 it on the classpath and add a handler 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
}
WebSocket Session
As a special case of request handling, you can define a WebSocket endpoint and manage the session. The server takes care of the opening handshake and passes the session to your handler.
app.websocket("/hello") { session =>
// Log ping message and send corresponding pong
session.onPing { data =>
session.logger.info("Received ping message.")
session.pong(data)
}
// Log pong message
session.onPong { data =>
session.logger.info("Received pong message.")
}
// Log text message and close session after sending reply
session.onText { message =>
session.logger.info(s"Received text message: $message")
session.send("Goodbye.")
session.close()
}
// Log status code when session is closed
session.onClose { status =>
session.logger.info(s"Session closed: $status")
}
// Open session to incoming messages
session.open()
// Send ping message
session.ping()
}
See WebSocketSession in scaladoc for additional details.
Error Handler
You can define an ErrorHandler
to handle exceptions thrown from your request handlers.
import scamper.ResponseStatus.Registry.{ BadRequest, InternalServerError }
// Accept Throwable and HttpRequest; return 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.ServerHttpRequest
val app = HttpServer.app()
// Mount router to /api
app.route("/api") { router =>
val messages = Map(1 -> "Hello, world!", 2 -> "Goodbye, cruel world!")
// Map handler to /api/messages
router.get("/messages") { req =>
Ok(messages.mkString("\r\n"))
}
// Map handler 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 a request handler 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.ServerHttpResponse
// Gzip response body if not empty
app.outgoing { res =>
res.body.isKnownEmpty match {
case true => res
case false => res.setGzipContentEncoding()
}
}
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.crt"))
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 application has been configured, you can 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, cruel world.
API Documentation
See scaladoc for additional details.
License
Scamper is licensed under the Apache License, Version 2. See LICENSE file for more information.