使用HTTParty检索JSON时出现“嵌套太深"错误 [英] 'Nesting too deep' error while retrieving JSON using HTTParty
问题描述
我正在为reddit api写一个非常简单的代理包装，这样我就可以发出跨域JSONP请求(reddit不允许进行JSONP调用).
I am writing a very simple proxy wrapper for the reddit api so I can make cross domain JSONP requests (reddit does not allow JSONP calls to my knowledge).
我正在使用HTTParty gem进行呼叫并检索响应，然后立即将其呈现为json.
I am using the HTTParty gem to make the call out and retrieve the response, which I immediately render out as json.
到目前为止，我正在使用此路由检索subreddit json完全正常:
I am retrieving the subreddit json perfectly fine so far with this as my route:
match "r/:name" => "api#subreddit"
...这是我的控制器操作:
... and this as my controller action:
def subreddit
render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/.json"), :callback => params[:callback]
end
作为示例，返回的JSON与此类似: http://www .reddit.com/r/pics/.json
As an example, the JSON that comes back is similar to this: http://www.reddit.com/r/pics/.json
我的问题是，当我尝试获取特定线程的注释时.
My problem is when I attempt to grab the comments for a particular thread.
我的路线是这样的:
match "r/:name/comments/:id" => "api#comments"
...而我的控制器动作是这样:
... and my controller action is this:
def comments
render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/comments/" + params[:id] + "/.json"), :callback => params[:callback]
end
我想要返回的JSON可以在这里看到: http://www.reddit.com/r/pics/comments/rhzgc/.json
The JSON that I want back can be seen here: http://www.reddit.com/r/pics/comments/rhzgc/.json
但是，当我调用此操作时，会收到以下错误消息:
When I call this action, however, I receive the following error message:
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'
我在这里做错了什么?如果JSON太大而无法解析(我很难相信！)我该怎么办?
What am I doing wrong here? If the JSON is too big to parse (I find that sort of hard to believe!) what can I do?
看起来像回到标准NET :: HTTP lib解决了我的问题:
Looks like dropping back to the standard NET::HTTP lib solved my problem:
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!
...但是我仍然很好奇为什么我无法使用HTTParty进行相同的调用！
... but I still am curious why I am failing this same call with HTTParty!
感谢您的帮助！
推荐答案
不是JSON太大.它嵌套得太深了. HTTParty尝试解码它自动获得的结果.遵循堆栈跟踪和HTTParty依赖关系，它依赖于使用json gem的multi_json.
It's not that the JSON is too large. It's nested too deeply. HTTParty tries to decode the results that it gets automatically. Following your stack trace, and the HTTParty dependencies, it relies on multi_json which is using the json gem.
在json内，有 lib/json/pure/parser.rb .默认的最大深度设置是在其中设置的，特别是在第79行.返回的JSON中的某个深度为20层以上，从而触发异常.
Inside of json there is lib/json/pure/parser.rb. The default max depth set is set in there, specifically on line 79. Something in your returned JSON is 20+ levels deep, triggering the exception.
if !opts.key?(:max_nesting) # defaults to 19
@max_nesting = 19
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