Added JSON body parsing

spec/kemal_handler_spec.cr

@@ -40,4 +40,66 @@ describe "Kemal::Handler" do
     response = kemal.call(request)
     response.body.should eq("hello world")
   end
+
+  it "parses simple JSON body" do
+    kemal = Kemal::Handler.new
+    kemal.add_route "POST", "/" do |env|
+      name = env.params["name"]
+      age = env.params["age"]
+      "Hello #{name} Age #{age}"
+    end
+
+    json_payload = {"name": "Serdar", "age": 26}
+    request = HTTP::Request.new(
+      "POST",
+      "/",
+      body: json_payload.to_json,
+      headers: HTTP::Headers{"Content-Type": "application/json"},
+    )
+
+    response = kemal.call(request)
+    response.body.should eq("Hello Serdar Age 26")
+  end
+
+  it "parses JSON with string array" do
+    kemal = Kemal::Handler.new
+    kemal.add_route "POST", "/" do |env|
+      skills = env.params["skills"] as Array
+      "Skills #{skills.each.join(',')}"
+    end
+
+    json_payload = {"skills": ["ruby", "crystal"]}
+    request = HTTP::Request.new(
+      "POST",
+      "/",
+      body: json_payload.to_json,
+      headers: HTTP::Headers{"Content-Type": "application/json"},
+    )
+
+    response = kemal.call(request)
+    response.body.should eq("Skills ruby,crystal")
+  end
+
+  it "parses JSON with json object array" do
+    kemal = Kemal::Handler.new
+    kemal.add_route "POST", "/" do |env|
+      skills = env.params["skills"] as Array
+      skills_from_languages = skills.map do |skill|
+        skill = skill as Hash
+        skill["language"]
+      end
+      "Skills #{skills_from_languages.each.join(',')}"
+    end
+
+    json_payload = {"skills": [{"language": "ruby"}, {"language": "crystal"}]}
+    request = HTTP::Request.new(
+      "POST",
+      "/",
+      body: json_payload.to_json,
+      headers: HTTP::Headers{"Content-Type": "application/json"},
+    )
+
+    response = kemal.call(request)
+    response.body.should eq("Skills ruby,crystal")
+  end
 end

spec/param_parser_spec.cr

@@ -30,6 +30,20 @@ describe "ParamParser" do
     params.should eq({"hasan" => "cemal", "name" => "serdar", "age" => "99"})
   end
 
+  it "parses request body" do
+    route = Route.new "POST", "/" { }
+
+    request = HTTP::Request.new(
+      "POST",
+      "/",
+      body: "{\"name\": \"Serdar\"}",
+      headers: HTTP::Headers{"Content-Type": "application/json"},
+    )
+
+    params = Kemal::ParamParser.new(route, request).parse
+    params.should eq({"name": "Serdar"})
+  end
+
   context "when content type is incorrect" do
     it "does not parse request body" do
       route = Route.new "POST", "/" do |env|

src/kemal/param_parser.cr

@@ -1,13 +1,19 @@
+require "json"
+
 # ParamParser parses the request contents including query_params and body
 # and converts them into a params hash which you can within the environment
 # context.
+
+alias AllParamTypes = Nil | String | Int64 | Float64 | Bool | Hash(String, JSON::Type) | Array(JSON::Type)
+
 class Kemal::ParamParser
   URL_ENCODED_FORM = "application/x-www-form-urlencoded"
+  APPLICATION_JSON = "application/json"
 
   def initialize(@route, @request)
     @route_components = route.components
     @request_components = request.path.not_nil!.split "/"
-    @params = {} of String => String
+    @params = {} of String => AllParamTypes
   end
 
   def parse
@@ -18,6 +24,7 @@ class Kemal::ParamParser
   def parse_request
     parse_query
     parse_body
+    parse_json
     @params
   end
 
@@ -30,6 +37,15 @@ class Kemal::ParamParser
     parse_part(@request.query)
   end
 
+  def parse_json
+    return unless @request.headers["Content-Type"]? == APPLICATION_JSON
+    body = @request.body as String
+    json = JSON.parse(body) as Hash
+    json.each do |k, v|
+      @params[k as String] = v as AllParamTypes
+    end
+  end
+
   def parse_part(part)
     return unless part
     HTTP::Params.parse(part) do |key, value|