HTTP and REST client for Crystal, inspired by the Ruby's RestClient gem.

Beloved features:

• Redirects support.
• HTTP(S) proxy support.
• Elegant Key/Value headers, cookies, query params, and form data.
• Multipart file uploads.
• JSON request with the appropriate HTTP headers.
• Streaming requests.
• International Domain Names.
• Digest access authentication.
• Logging.

Hopefully, someday I can remove this shard though. Ideally, Crystal's standard library would do all this already.

Installation

Add this to your application's shard.yml:

dependencies:
  crest:
    github: mamantoha/crest

Usage

require "crest"

Basic usage:

Crest.get(
  "http://httpbin.org/get",
  params: {:lang => "en"},
  user_agent: "Mozilla/5.0"
)
# curl -L http://httpbin.org/get?lang=en -H 'User-Agent: Mozilla/5.0'

Crest.post(
  "http://httpbin.org/post",
  {:age => 27, :name => {:first => "Kurt", :last => "Cobain"}}
)
# curl -L --data "age=27&name[first]=Kurt&name[last]=Cobain" -X POST "http://httpbin.org/post"

Crest.post(
  "http://httpbin.org/post",
  {"file" => File.open("avatar.png"), "name" => "John"}
)
# curl -X POST http://httpbin.org/post -F 'file=@/path/to/avatar.png' -F 'name=John' -H 'Content-Type: multipart/form-data'

response = Crest.post(
  "http://httpbin.org/post",
  {:age => 27, :name => {:first => "Kurt", :last => "Cobain"}},
  json: true
)
# curl -X POST http://httpbin.org/post -d '{"age":27,"name":{"first":"Kurt","last":"Cobain"}}' -H 'Content-Type: application/json'

Request

Crest::Request accept next parameters:

Mandatory parameters:

• :method - HTTP method (:get. :post, :put, :patch, :delete, :options, head)
• :url - URL (e.g.: http://httpbin.org/ip)

Optional parameters:

• :form - a hash containing form data (or a raw string or IO or Bytes)
• :headers - a hash containing the request headers
• :cookies - a hash containing the request cookies
• :params - a hash that represent query params (or a raw string) - a string separated from the preceding part by a question mark (?) and a sequence of attribute–value pairs separated by a delimiter (&)
• :params_encoder params encoder (default to Crest::FlatParamsEncoder)
• :auth - access authentication method basic or digest (default to basic)
• :user and :password - for authentication
• :tls - client certificates, you can pass in a custom OpenSSL::SSL::Context::Client (default to nil)
• :p_addr, :p_port, :p_user, and :p_pass - specify a per-request proxy by passing these parameters
• :json - make a JSON request with the appropriate HTTP headers (default to false)
• :multipart make a multipart request with the appropriate HTTP headers even if not sending a file (default to false)
• :user_agent - set "User-Agent" HTTP header (default to Crest::USER_AGENT)
• :max_redirects - maximum number of redirects (default to 10)
• :logging - enable logging (default to false)
• :logger - set logger (default to Crest::CommonLogger)
• :handle_errors - error handling (default to true)
• :close_connection - close the connection after request is completed (default to true)
• :http_client - instance of HTTP::Client
• :read_timeout - read timeout (default to nil)
• :write_timeout - write timeout (default to nil)
• :connect_timeout - connect timeout (default to nil)

More detailed examples:

request = Crest::Request.new(:post,
  "http://httpbin.org/post",
  headers: {"Content-Type" => "application/json"},
  form: {:width => 640, "height" => "480"}
)
request.execute
# curl -L --data "width=640&height=480" --header "Content-Type: application/json" -X POST "http://httpbin.org/post"

Crest::Request.execute(:get,
  "http://httpbin.org/get",
  params: {:width => 640, "height" => "480"},
  headers: {"Content-Type" => "application/json"}
)
# curl -L --header "Content-Type: application/json" "http://httpbin.org/get?width=640&height=480"

Crest::Request.new(:post, "http://httpbin.org/post", {:foo => "bar"}, json: true)

# curl -X POST http://httpbin.org/post -d '{\"foo\":\"bar\"}' -H 'Content-Type: application/json'"

Crest::Request.get(
  "http://httpbin.org/get",
  p_addr: "127.0.0.1",
  p_port: 3128,
  p_user: "admin",
  p_pass: "1234"
)
# curl -L --proxy admin:[email protected]:3128 "http://httpbin.org/get"

A block can be passed to the Crest::Request initializer.

This block will then be called with the Crest::Request.

request = Crest::Request.new(:get, "http://httpbin.org/headers") do |request|
  request.headers.add("foo", "bar")
end

request.execute
# curl -L --header "foo: bar" http://httpbin.org/headers

Resource

A Crest::Resource class can be instantiated for access to a RESTful resource, including authentication, proxy and logging.

Additionally, you can set default params, headers, and cookies separately. So you can use Crest::Resource to share common params, headers, and cookies.

The final parameters consist of:

• default parameters from initializer
• parameters provided in call method (get, post, etc)

This is especially useful if you wish to define your site in one place and call it in multiple locations.

resource = Crest::Resource.new(
  "http://httpbin.org",
  params: {"key" => "value"},
  headers: {"Content-Type" => "application/json"},
  cookies: {"lang" => "uk"}
)

resource["/get"].get(
  headers: {"Auth-Token" => "secret"}
)

resource["/post"].post(
  {:height => 100, "width" => "100"},
  params: {:secret => "secret"}
)

Use the [] syntax to allocate subresources:

site = Crest::Resource.new("http://httpbin.org")

site["/post"].post({:param1 => "value1", :param2 => "value2"})
# curl -L --data "param1=value1&param2=value2" -X POST http://httpbin.org/post

You can pass suburl through Request#http_verb methods:

site = Crest::Resource.new("http://httpbin.org")

site.post("/post", {:param1 => "value1", :param2 => "value2"})
# curl -L --data "param1=value1&param2=value2" -X POST http://httpbin.org/post

site.get("/get", params: {:status => "active"})
# curl -L http://httpbin.org/get?status=active

A block can be passed to the Crest::Resource instance.

This block will then be called with the Crest::Resource.

resource = Crest::Resource.new("http://httpbin.org") do |resource|
  resource.headers.merge!({"foo" => "bar"})
end

resource["/headers"].get

With HTTP basic authentication:

resource = Crest::Resource.new(
  "http://httpbin.org/basic-auth/user/passwd",
  user: "user",
  password: "passwd"
)

With Proxy:

resource = Crest::Resource.new(
  "http://httpbin.org/get",
  p_addr: "localhost",
  p_port: 3128
)

Result handling

The result of a Crest::Request and Crest::Resource is a Crest::Response object.

Response objects have several useful methods:

• Response#body: The response body as a String
• Response#body_io: The response body as a IO
• Response#status: The response status as a HTTP::Status
• Response#status_code: The HTTP response code
• Response#headers: A hash of HTTP response headers
• Response#cookies: A hash of HTTP cookies set by the server
• Response#request: The Crest::Request object used to make the request
• Response#http_client_res: The HTTP::Client::Response object
• Response#history: A list of each response received in a redirection chain

Exceptions

• for status codes between 200 and 207, a Crest::Response will be returned
• for status codes 301, 302, 303 or 307, the redirection will be followed and the request transformed into a GET
• for other cases, a Crest::RequestFailed holding the Crest::Response will be raised
• call .response on the exception to get the server's response

Crest.get("http://httpbin.org/status/404")
# => HTTP status code 404: Not Found (Crest::NotFound)

begin
  Crest.get("http://httpbin.org/status/404")
rescue ex : Crest::NotFound
  puts ex.response
end

To not raise exceptions but return the Crest::Response you can set handle_errors to false.

response = Crest.get("http://httpbin.org/status/404", handle_errors: false) do |resp|
  case resp
  when .success?
    puts resp.body_io.gets_to_end
  when .client_error?
    puts "Client error"
  when .server_error?
    puts "Server error"
  end
end
# => Client error

response.status_code # => 404

But note that it may be more straightforward to use exceptions to handle different HTTP error response cases:

response = begin
  Crest.get("http://httpbin.org/status/404")
rescue ex : Crest::NotFound
  puts "Not found"
  ex.response
rescue ex : Crest::InternalServerError
  puts "Internal server error"
  ex.response
end
# => Not found

response.status_code # => 404

Parameters serializer

Crest::ParamsEncoder class is used to encode parameters.

The encoder affect both how crest processes query strings and how it serializes POST bodies.

The default encoder is Crest::FlatParamsEncoder.

It provides #encode method, which converts the given params into a URI query string:

Crest::FlatParamsEncoder.encode({"a" => ["one", "two", "three"], "b" => true, "c" => "C", "d" => 1})
# => 'a[]=one&a[]=two&a[]=three&b=true&c=C&d=1'

Custom parameters serializers

You can build a custom params encoder.

The value of Crest params_encoder can be any subclass of Crest::ParamsEncoder that implement #encode(Hash) #=> String

Also Crest include other encoders.

Crest::NestedParamsEncoder

response = Crest.post(
  "http://httpbin.org/post",
  {"size" => "small", "topping" => ["bacon", "onion"]},
  params_encoder: Crest::NestedParamsEncoder
)

# => curl -X POST http://httpbin.org/post -d 'size=small&topping=bacon&topping=onion' -H 'Content-Type: application/x-www-form-urlencoded'

Crest::EnumeratedFlatParamsEncoder

response = Crest.post(
  "http://httpbin.org/post",
  {"size" => "small", "topping" => ["bacon", "onion"]},
  params_encoder: Crest::EnumeratedFlatParamsEncoder
)

# => curl -X POST http://httpbin.org/post -d 'size=small&topping[1]=bacon&topping[2]=onion' -H 'Content-Type: application/x-www-form-urlencoded'

Crest::ZeroEnumeratedFlatParamsEncoder

response = Crest.post(
  "http://httpbin.org/post",
  {"size" => "small", "topping" => ["bacon", "onion"]},
  params_encoder: Crest::ZeroEnumeratedFlatParamsEncoder
)

# => curl -X POST http://httpbin.org/post -d 'size=small&topping[0]=bacon&topping[1]=onion' -H 'Content-Type: application/x-www-form-urlencoded'

Streaming responses

Normally, when you use Crest, Crest::Request or Crest::Resource methods to retrieve data, the entire response is buffered in memory and returned as the response to the call.

However, if you are retrieving a large amount of data, for example, an iso, or any other large file, you may want to stream the response directly to disk rather than loading it into memory. If you have a very large file, it may become impossible to load it into memory.

If you want to stream the data from the response to a file as it comes, rather than entirely in memory, you can pass a block to which you pass a additional logic, which you can use to stream directly to a file as each chunk is received.

With a block, an Crest::Response body is returned and the response's body is available as an IO by invoking Crest::Response#body_io.

The following is an example:

Crest.get("https://github.com/crystal-lang/crystal/archive/1.0.0.zip") do |resp|
  filename = resp.filename || "crystal.zip"

  File.open(filename, "w") do |file|
    IO.copy(resp.body_io, file)
  end
end

Advanced Usage

This section covers some of crest more advanced features.

Multipart

Yeah, that's right! This does multipart sends for you!

file = File.open("#{__DIR__}/example.png")
Crest.post("http://httpbin.org/post", {:image => file})

file_content = "id,name\n1,test"
file = IO::Memory.new(file_content)
Crest.post("http://httpbin.org/post", {"data.csv" => file})

file = File.open("#{__DIR__}/example.png")
resource = Crest::Resource.new("https://httpbin.org")
response = resource["/post"].post({:image => file})

JSON payload

crest speaks JSON natively by passing json: true argument to crest.

Crest.post("http://httpbin.org/post", {:foo => "bar"}, json: true)

As well you can serialize your form to a string by itself before passing it to crest.

Crest.post(
  "http://httpbin.org/post",
  {:foo => "bar"}.to_json
  headers: {"Accept" => "application/json", "Content-Type" => "application/json"},
)

Headers

Request headers can be set by passing a hash containing keys and values representing header names and values:

response = Crest.get(
  "http://httpbin.org/bearer",
  headers: {"Authorization" => "Bearer cT0febFoD5lxAlNAXHo6g"}
)
response.headers
# => {"Authorization" => ["Bearer cT0febFoD5lxAlNAXHo6g"]}

Cookies

Request and Response objects know about HTTP cookies, and will automatically extract and set headers for them as needed:

response = Crest.get(
  "http://httpbin.org/cookies/set",
  params: {"k1" => "v1", "k2" => "v2"}
)
response.cookies
# => {"k1" => "v1", "k2" => "v2"}

response = Crest.get(
  "http://httpbin.org/cookies",
  cookies: {"k1" => "v1", "k2" => {"kk2" => "vv2"}}
)
response.cookies
# => {"k1" => "v1", "k2[kk2]" => "vv2"}

Basic access authentication

For basic access authentication for an HTTP user agent you should to provide a user name and password when making a request.

Crest.get(
  "http://httpbin.org/basic-auth/user/passwd",
  user: "user",
  password: "passwd"
)
# curl -L --user user:passwd http://httpbin.org/basic-auth/user/passwd

Digest access authentication

For digest access authentication for an HTTP user agent you should to provide a user name and password when making a request.

Crest.get(
  "https://httpbin.org/digest-auth/auth/user/passwd/MD5",
  auth: "digest",
  user: "user",
  password: "passwd"
)
# curl -L --digest --user user:passwd https://httpbin.org/digest-auth/auth/user/passwd/MD5

SSL/TLS support

If tls is given it will be used:

Crest.get("https://expired.badssl.com", tls: OpenSSL::SSL::Context::Client.insecure)

Proxy

If you need to use a proxy, you can configure individual requests with the proxy host and port arguments to any request method:

Crest.get(
  "http://httpbin.org/ip",
  p_addr: "localhost",
  p_port: 3128
)

To use authentication with your proxy, use next syntax:

Crest.get(
  "http://httpbin.org/ip",
  p_addr: "localhost",
  p_port: 3128,
  p_user: "user",
  p_pass: "qwerty"
)

Logging

Logger class is completely taken from halite shard. Thanks icyleaf!

By default, the Crest does not enable logging. You can enable it per request by setting logging: true:

Crest.get("http://httpbin.org/get", logging: true)

Filter sensitive information from logs with a regex matcher

resource = Crest::Request.get("http://httpbin.org/get", params: {api_key => "secret"}, logging: true) do |request|
  request.logger.filter(/(api_key=)(\w+)/, "\\1[REMOVED]")
end

# => crest | 2018-07-04 14:49:49 | GET | http://httpbin.org/get?api_key=[REMOVED]

Customize logger

You can create the custom logger by integration Crest::Logger abstract class. Here has two methods must be implement: Crest::Logger.request and Crest::Logger.response.

class MyLogger < Crest::Logger
  def request(request)
    @logger.info { ">> | %s | %s" % [request.method, request.url] }
  end

  def response(response)
    @logger.info { "<< | %s | %s" % [response.status_code, response.url] }
  end
end

Crest.get("http://httpbin.org/get", logging: true, logger: MyLogger.new)

Redirection

By default, crest will follow HTTP 30x redirection requests.

To disable automatic redirection, set :max_redirects => 0.

Crest::Request.execute(method: :get, url: "http://httpbin.org/redirect/1", max_redirects: 0)
# => Crest::Found: 302 Found

Access HTTP::Client

You can access HTTP::Client via the http_client instance method.

This is usually used to set additional options (e.g. read timeout, authorization header etc.)

client = HTTP::Client.new("httpbin.org")
client.read_timeout = 1.second

begin
  Crest::Request.new(:get,
    "http://httpbin.org/delay/10",
    http_client: client
  )
rescue IO::TimeoutError
  puts "Timeout!"
end

client = HTTP::Client.new("httpbin.org")
client.read_timeout = 1.second

begin
  resource = Crest::Resource.new("http://httpbin.org", http_client: client)
  resource.get("/delay/10")
rescue IO::TimeoutError
  puts "Timeout!"
end

Convert Request object to cURL command

Use to_curl method on instance of Crest::Request to convert request to cURL command.

request = Crest::Request.new(
  :post,
  "http://httpbin.org/post",
  {"title" => "New Title", "author" => "admin"}
)
request.to_curl
# => curl -X POST http://httpbin.org/post -d 'title=New+Title&author=admin' -H 'Content-Type: application/x-www-form-urlencoded'

request = Crest::Request.new(
  :get,
  "http://httpbin.org/basic-auth/user/passwd",
  user: "user",
  password: "passwd"
)
request.to_curl
# => curl -X GET http://httpbin.org/basic-auth/user/passwd --user user:passwd

Also you can directly use Crest::Curlify which accept instance of Crest::Request

request = Crest::Request.new(:get, "http://httpbin.org")
Crest::Curlify.new(request).to_curl
# => curl -X GET http://httpbin.org

Params decoder

Crest::ParamsDecoder is a module for decoding query-string into parameters.

query = "size=small&topping[1]=bacon&topping[2]=onion"
Crest::ParamsDecoder.decode(query)
# => {"size" => "small", "topping" => ["bacon", "onion"]}

Development

Install dependencies:

shards

To run test:

crystal spec

Workbook

crystal play
open http://localhost:8080

Then select the Workbook -> Requests from the menu.

Contributing

1. Fork it (https://github.com/mamantoha/crest/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

Anton Maminov 💻

Chao Yang 💻

psikoz 🎨

jphaward 💻

License

Copyright: 2017-2025 Anton Maminov ([email protected])

This library is distributed under the MIT license. Please see the LICENSE file.