blocks|key|590376|text|一位朋友向我推荐了一个优雅的解决方案，它不仅可以处理404个错误，还可以处理500个错误。事实上，它会处理所有错误。关键是，每个错误都会生成一个异常，该异常会通过机架中间件堆栈向上传播，直到被其中一个中间件处理。如果你有兴趣了解更多，你可以看this+excellent+screencast。Rails有自己的异常处理程序，但您可以使用文档较少的exceptions_app配置选项来覆盖它们。现在，您可以编写自己的中间件，也可以将错误路由回rails，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|590377|#+In+your+config/application.rb
config.exceptions_app+=+self.routes|code-block|syntax|javascript|590378|然后，您只需在config/routes.rb中匹配这些路由|590379|get+"/404"+=>+"errors#not_found"
get+"/500"+=>+"errors#exception"|590380|然后您只需创建一个控制器来处理此问题。|590381|class+ErrorsController+<+ActionController::Base
++def+not_found
++++if+env["REQUEST_PATH"]+=~+/%5E\/api/
++++++render+:json+=>+{:error+=>+"not-found"}.to_json,+:status+=>+404
++++else
++++++render+:text+=>+"404+Not+found",+:status+=>+404+#+You+can+render+your+own+template+here
++++end
++end

++def+exception
++++if+env["REQUEST_PATH"]+=~+/%5E\/api/
++++++render+:json+=>+{:error+=>+"internal-server-error"}.to_json,+:status+=>+500
++++else
++++++render+:text+=>+"500+Internal+Server+Error",+:status+=>+500+#+You+can+render+your+own+template+here
++++end
++end
end|590382|最后要补充的一点是:在开发环境中，rails通常不会呈现404或500页，而是打印回溯。如果你想在开发模式下看到你的ErrorsController在运行，那么在你的config/enviroments/development.rb文件中禁用回溯功能。|590383|config.consider_all_requests_local+=+false|590384|entityMap|0|LINK|mutability|MUTABLE|url|http://railscasts.com/episodes/151-rack-middleware^0|4U|E|3D|P|0|0|0|7|G|0|0|0|0|1M|G|2B|X|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1B|8|@$9|1C|A|1D|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1E|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1F|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1H|8|@$9|1I|A|1J|B|C]|$9|1K|A|1L|B|C]]|D|@]|E|$]]|$1|U|3|V|5|H|7|1M|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13]]]]

A friend pointed me towards a elegant solution that does not only handle 404 but also 500 errors. In fact, it handles every error. The key is, that every error generates an exception that propagates upwards through the stack of rack middlewares until it is handled by one of them. If you are interested in learning more, you can watch <a href="http://railscasts.com/episodes/151-rack-middleware">this excellent screencast</a>. Rails has it own handlers for exceptions, but you can override them by the less documented <code>exceptions_app</code> config option. Now, you can write your own middleware or you can route the error back into rails, like this:

<pre><code># In your config/application.rb
config.exceptions_app = self.routes
</code></pre>

Then you just have to match these routes in your <code>config/routes.rb</code>:

<pre><code>get "/404" =&gt; "errors#not_found"
get "/500" =&gt; "errors#exception"
</code></pre>

And then you just create a controller for handling this.

<pre><code>class ErrorsController &lt; ActionController::Base
 def not_found
 if env["REQUEST_PATH"] =~ /^\/api/
 render :json =&gt; {:error =&gt; "not-found"}.to_json, :status =&gt; 404
 else
 render :text =&gt; "404 Not found", :status =&gt; 404 # You can render your own template here
 end
 end

 def exception
 if env["REQUEST_PATH"] =~ /^\/api/
 render :json =&gt; {:error =&gt; "internal-server-error"}.to_json, :status =&gt; 500
 else
 render :text =&gt; "500 Internal Server Error", :status =&gt; 500 # You can render your own template here
 end
 end
end
</code></pre>

One last thing to add: In the development environment, rails usally does not render the 404 or 500 pages but prints a backtrace instead. If you want to see your <code>ErrorsController</code> in action in development mode, then disable the backtrace stuff in your <code>config/enviroments/development.rb</code> file.

<pre><code>config.consider_all_requests_local = false
</code></pre>

blocks|key|590441|text|我喜欢创建一个单独的API控制器来设置格式(json)和特定于api的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|590442|class+ApiController+<+ApplicationController
++respond_to+:json

++rescue_from+ActiveRecord::RecordNotFound,+with:+:not_found
++#+Use+Mongoid::Errors::DocumentNotFound+with+mongoid

++def+not_found
++++respond_with+'{"error":+"not_found"}',+status:+:not_found
++end
end|code-block|syntax|javascript|590443|RSpec测试：|590444|++it+'should+return+404'+do
++++get+"/api/route/specific/to/your/app/",+format:+:json
++++expect(response.status).to+eq(404)
++end|590445|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I like to create a separate API controller that sets the format (json) and api-specific methods:

<pre><code>class ApiController &lt; ApplicationController
 respond_to :json

 rescue_from ActiveRecord::RecordNotFound, with: :not_found
 # Use Mongoid::Errors::DocumentNotFound with mongoid

 def not_found
 respond_with '{"error": "not_found"}', status: :not_found
 end
end
</code></pre>

RSpec test:

<pre><code> it 'should return 404' do
 get "/api/route/specific/to/your/app/", format: :json
 expect(response.status).to eq(404)
 end
</code></pre>

I am having a normal HTML frontend and a JSON API in my Rails App. Now, if someone calls <code>/api/not_existent_method.json</code> it returns the default HTML 404 page. Is there any way to change this to something like <code>{"error": "not_found"}</code> while leaving the original 404 page for the HTML frontend intact?

Need to return JSON-formatted 404 error in Rails

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我有一个普通的HTML前端和一个JSON API在我的Rails应用程序中。现在，如果有人调用/api/not_existent_method.json，它将返回默认的HTML404页面。有没有办法将其更改为类似于{"error": "not_found"}的内容，同时保持原始的404页面不变？

问需要在Rails中返回JSON格式的404错误
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