使用HTTParty检索JSON时“嵌套太深”错误
我正在为reddit api编写一个非常简单的代理包装器，所以我可以创建跨域JSONP请求（reddit不允许JSONP调用我的知识）。
我正在使用HTTParty gem来调用并检索响应，我立即将其呈现为json。
到目前为止，我正在检索subreddit json，这是我的路线：
match "r/:name" => "api#subreddit" ……这是我的控制器动作：
def subreddit render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/.json"), :callback => params[:callback] end
例如，返回的JSON类似于： http ： //www.reddit.com/r/pics/.json
我的问题是当我试图获取特定线程的注释时。
我的路线是这样的：
match "r/:name/comments/:id" => "api#comments"
……我的控制器动作如下：
def comments render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/comments/" + params[:id] + "/.json"), :callback => params[:callback] end
我想要的JSON可以在这里看到： http ： //www.reddit.com/r/pics/comments/rhzgc/.json
但是，当我调用此操作时，收到以下错误消息：
MultiJson::DecodeError in ApiController#comments Nesting of 20 is too deep
完整的堆栈跟踪如下：
json (1.6.6) lib/json/common.rb:148:in `parse' json (1.6.6) lib/json/common.rb:148:in `parse' multi_json (1.2.0) lib/multi_json/engines/json_common.rb:9:in `decode' multi_json (1.2.0) lib/multi_json.rb:81:in `decode' httparty (0.8.1) lib/httparty/parser.rb:116:in `json' httparty (0.8.1) lib/httparty/parser.rb:136:in `parse_supported_format' httparty (0.8.1) lib/httparty/parser.rb:103:in `parse' httparty (0.8.1) lib/httparty/parser.rb:66:in `call' httparty (0.8.1) lib/httparty/request.rb:222:in `parse_response' httparty (0.8.1) lib/httparty/request.rb:192:in `handle_response' httparty (0.8.1) lib/httparty/request.rb:75:in `perform' httparty (0.8.1) lib/httparty.rb:391:in `perform_request' httparty (0.8.1) lib/httparty.rb:343:in `get' httparty (0.8.1) lib/httparty.rb:423:in `get' app/controllers/api_controller.rb:12:in `comments' actionpack (3.1.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (3.1.1) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.1.1) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (3.1.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.1.1) lib/active_support/callbacks.rb:416:in `_run__2872109728488784816__process_action__2261783022290592822__callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.1.1) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (3.1.1) lib/action_controller/metal/rescue.rb:17:in `process_action' actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument' activesupport (3.1.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument' activesupport (3.1.1) lib/active_support/notifications.rb:53:in `instrument' actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:29:in `process_action' actionpack (3.1.1) lib/action_controller/metal/params_wrapper.rb:201:in `process_action' activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (3.1.1) lib/abstract_controller/base.rb:121:in `process' actionpack (3.1.1) lib/abstract_controller/rendering.rb:45:in `process' actionpack (3.1.1) lib/action_controller/metal.rb:193:in `dispatch' actionpack (3.1.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' actionpack (3.1.1) lib/action_controller/metal.rb:236:in `block in action' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `call' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `dispatch' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:29:in `call' rack-mount (0.8.3) lib/rack/mount/route_set.rb:152:in `block in call' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `block in recognize' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:89:in `optimized_each' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:95:in `recognize' rack-mount (0.8.3) lib/rack/mount/route_set.rb:141:in `call' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:532:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' rack (1.3.6) lib/rack/etag.rb:23:in `call' rack (1.3.6) lib/rack/conditionalget.rb:25:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/head.rb:14:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/params_parser.rb:21:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/flash.rb:243:in `call' rack (1.3.6) lib/rack/session/abstract/id.rb:195:in `context' rack (1.3.6) lib/rack/session/abstract/id.rb:190:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/cookies.rb:331:in `call' activerecord (3.1.1) lib/active_record/query_cache.rb:62:in `call' activerecord (3.1.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:477:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call' activesupport (3.1.1) lib/active_support/callbacks.rb:392:in `_run_call_callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:28:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/reloader.rb:68:in `call' rack (1.3.6) lib/rack/sendfile.rb:101:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/remote_ip.rb:48:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call' railties (3.1.1) lib/rails/rack/logger.rb:13:in `call' rack (1.3.6) lib/rack/methodoverride.rb:24:in `call' rack (1.3.6) lib/rack/runtime.rb:17:in `call' activesupport (3.1.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call' rack (1.3.6) lib/rack/lock.rb:15:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/static.rb:53:in `call' railties (3.1.1) lib/rails/engine.rb:456:in `call' railties (3.1.1) lib/rails/rack/content_length.rb:16:in `call' railties (3.1.1) lib/rails/rack/log_tailer.rb:14:in `call' rack (1.3.6) lib/rack/handler/webrick.rb:59:in `service' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'
我在这做错了什么？ 如果JSON太大而无法解析（我觉得很难相信！）我该怎么办？
编辑：
看起来像回退到标准的NET :: HTTP lib解决了我的问题：
uri = URI.parse("http://www.reddit.com/r/pics/comments/rhzgc/.json") response = Net::HTTP.get_response(uri) render :json => response.body, :callback => params[:callback] #OK!
…但我仍然很好奇为什么我在与HTTParty的同一个电话中失败了！
谢谢您的帮助！
这并不是说JSON太大了。 它的嵌套太深了。 HTTParty尝试解码它自动获得的结果。 在堆栈跟踪和HTTParty依赖关系之后，它依赖于使用json gem的multi_json 。
在json里面有lib/json/pure/parser.rb 。 默认的最大深度设置在那里设置，特别是在第79行。返回的JSON中的某些东西深度超过20级，触发exception。
if !opts.key?(:max_nesting) # defaults to 19 @max_nesting = 19
看起来这可以通过调用to_json并设置max_nesting选项来解决。
json = obj.to_json(max_nesting: 50)
通过将以下内容添加到我的Gemfile中切换到OJ JSON解析器：
gem 'oj'
这个问题解决了。