如何从Rails 4中的ActionDispatch :: ParamsParser :: ParseError中解救

Question

Rails 4添加了一个异常ActionDispatch :: ParamsParser :: ParseError异常,但由于它在中间件堆栈中,它似乎无法在普通控制器环境中获救.在json API应用程序中,我想用标准错误格式进行响应.

这个要点显示了插入中间件以拦截和响应的策略.遵循这种模式我有:

application.rb中:

module Traphos
  class Application < Rails::Application
    ....
    config.middleware.insert_before ActionDispatch::ParamsParser, "JSONParseError"
 end
end

中间件是:

class JSONParseError
  def initialize(app)
    @app = app
  end

  def call(env)
    begin
      @app.call(env)
    rescue ActionDispatch::ParamsParser::ParseError => e
      [422, {}, ['Parse Error']]
    end
  end
end

如果我在没有中间件的情况下运行测试,我会得到(spec):

Failures:

  1) Photo update attributes with non-parseable json
     Failure/Error: patch update_url, {:description => description}, "CONTENT_TYPE" => content_type, "HTTP_ACCEPT" => accepts, "HTTP_AUTHORIZATION" => @auth
     ActionDispatch::ParamsParser::ParseError:
       399: unexpected token at 'description=Test+New+Description]'

这正是我所期望的(ParseError,我无法rescue_from).

现在只需在上面的中间件中添加更改:

  2) Photo update attributes with non-parseable json
     Failure/Error: response.status.should eql(422)

       expected: 422
            got: 200

并且日志显示正在执行标准控制器操作并返回正常响应(尽管因为它没有接收任何参数而没有更新任何内容).

我的问题:

1. 如何从ParseError中解救并返回自定义响应.感觉就像我在正确的轨道,但不是那里.

2. 我无法弄清楚为什么,当异常被提出并获救时,控制器动作仍然继续进行.

非常感谢, - Kip

Answer 1

事实证明,在中间件堆栈中,可以使用例外应用程序配置ActionDispatch :: ShowExceptions.

module Traphos
  class Application < Rails::Application
    # For the exceptions app
    require "#{config.root}/lib/exceptions/public_exceptions"
    config.exceptions_app = Traphos::PublicExceptions.new(Rails.public_path)
  end
end

基于Rails,我现在使用的是:

module Traphos
  class PublicExceptions
    attr_accessor :public_path

    def initialize(public_path)
      @public_path = public_path
    end

    def call(env)
      exception    = env["action_dispatch.exception"]
      status       = code_from_exception(env["PATH_INFO"][1..-1], exception)
      request      = ActionDispatch::Request.new(env)
      content_type = request.formats.first
      body         = {:status => { :code => status, :exception => exception.class.name, :message => exception.message }}
      render(status, content_type, body)
    end

    private

    def render(status, content_type, body)
      format = content_type && "to_#{content_type.to_sym}"
      if format && body.respond_to?(format)
        render_format(status, content_type, body.public_send(format))
      else
        render_html(status)
      end
    end

    def render_format(status, content_type, body)
      [status, {'Content-Type' => "#{content_type}; charset=#{ActionDispatch::Response.default_charset}",
                'Content-Length' => body.bytesize.to_s}, [body]]
    end

    def render_html(status)
      found = false
      path = "#{public_path}/#{status}.#{I18n.locale}.html" if I18n.locale
      path = "#{public_path}/#{status}.html" unless path && (found = File.exist?(path))

      if found || File.exist?(path)
        render_format(status, 'text/html', File.read(path))
      else
        [404, { "X-Cascade" => "pass" }, []]
      end
    end

    def code_from_exception(status, exception)
      case exception
      when ActionDispatch::ParamsParser::ParseError
        "422"
      else
        status
      end
    end
  end
end

要在测试环境中使用它,需要设置配置变量(否则您将在开发和测试中获得标准异常处理).所以测试我有(编辑到只有关键部分):

describe Photo, :type => :api do
  context 'update' do
    it 'attributes with non-parseable json' do 

      Rails.application.config.consider_all_requests_local = false
      Rails.application.config.action_dispatch.show_exceptions = true

      patch update_url, {:description => description}
      response.status.should eql(422)
      result = JSON.parse(response.body)
      result['status']['exception'].should match(/ParseError/)

      Rails.application.config.consider_all_requests_local = true
      Rails.application.config.action_dispatch.show_exceptions = false
    end
  end
end

它以我需要的公共API方式执行,并且适用于我可能选择自定义的任何其他异常.