[英]How to make a post request with XMLHttpRequest object?
我在客戶端有一個JavaScript代碼段,該代碼段通過跨域從另一個Rails API應用程序請求數據。
var myData = { "event": {"name": "some event name", "property": "some value"} };
var request = new XMLHttpRequest();
request.open("POST", "http://localhost:3000/api/events", true);
request.setRequestHeader('Content-Type', 'application/json');
request.send(JSON.stringify(myData));
我想知道為什么要添加request.setRequestHeader('Content-Type','application / json'); 導致瀏覽器發送POST請求 ,但是如果沒有此語句,瀏覽器將發送OPTIONS請求 ?
另外,在運行上面的代碼時,在我的Rails應用程序中,我收到一個錯誤ActionController :: ParameterMissing-參數丟失或值為空:event :。 為什么瀏覽器不發送myData變量中的數據集?
版本信息:ruby 2.1.5p273,Rails 4.1.8
# routes.rb
Rails.application.routes.draw do
match '/api/events' => 'api/v1/events#create', via: :options
...
end
# app/controller/api/v1/events_controller.rb
class API::V1::EventsController < ApplicationController
skip_before_action :verify_authenticity_token
before_action :set_headers
def index
@events = Event.all
render json: @events, status: :ok
end
def show
@event = Event.find(params[:id])
render json: @event
end
def create
@event = Event.new(event_params)
if @event.save
render json: @event, status: :created
else
render @event.errors, status: :unprocessable_entity
end
end
def update
@event = Event.find(params[:id])
if @event.update(event_params)
raise "#{@event.name}"
head :no_content
else
render @event.errors, status: :unprocessable_entity
end
end
private
def event_params
params.require(:event).permit(:name, :property)
end
def set_headers
headers['Access-Control-Allow-Origin'] = '*'
headers['Access-Control-Expose-Headers'] = 'ETag'
headers['Access-Control-Allow-Methods'] = 'OPTIONS' #'GET, POST, PATCH, PUT, DELETE, OPTIONS, HEAD'
headers['Access-Control-Allow-Headers'] = '*,x-requested-with,Content-Type,If-Modified-Since,If-None-Match'
headers['Access-Control-Max-Age'] = '1728000'
end
end
# Rails log
Started OPTIONS "/api/events" for 127.0.0.1 at 2015-01-09 14:54:31 -0600
Processing by API::V1::EventsController#create as */*
Completed 400 Bad Request in 2ms
ActionController::ParameterMissing - param is missing or the value is empty: event:
actionpack (4.1.8) lib/action_controller/metal/strong_parameters.rb:187:in `require'
app/controllers/api/v1/events_controller.rb:39:in `event_params'
app/controllers/api/v1/events_controller.rb:18:in `create'
actionpack (4.1.8) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
...
瀏覽器針對每個跨域ajax發布請求發送OPTIONS請求,以檢查請求是否安全。 要了解更多信息,請搜索“ cors”。
要解決您的問題,請從控制器中刪除'set_header'before_filter
config.middleware.insert_before 0, "Rack::Cors" do allow do origins '*' resource '*', :headers => :any, :methods => [:get, :post, :options, :put, :head, :delete] end end
我將在執行此操作時使用jQuery,因為默認情況下它已在所有帶有Rails的頁面上。 您可以執行$.post('/api/events', myData)
,它將為您處理大量手動工作,並使它可以在多個瀏覽器中工作。 附帶一提,您無需將key
括在引號中。
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