多亏了机架中间件和Rails 3，你可以为每个请求输出漂亮的JSON，而无需更改应用程序的任何控制器。我已经编写了这样的中间件片段，我在浏览器和curl输出中得到了漂亮的打印JSON。

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

  def call(env)
    status, headers, response = @app.call(env)
    if headers["Content-Type"] =~ /^application\/json/
      obj = JSON.parse(response.body)
      pretty_str = JSON.pretty_unparse(obj)
      response = [pretty_str]
      headers["Content-Length"] = pretty_str.bytesize.to_s
    end
    [status, headers, response]
  end
end

上面的代码应该放在app/middleware/pretty_json_response中。您的Rails项目的rb。 最后一步是在config/environments/development.rb中注册中间件:

config.middleware.use PrettyJsonResponse

我不建议在生产中使用它。JSON的重新解析可能会降低你的产品应用的响应时间和吞吐量。最终，额外的逻辑，如'X-Pretty-Json: true'头可能会被引入，以触发手动curl请求按需格式化。

(在Rails 3.2.8-5.0.0, Ruby 1.9.3-2.2.0, Linux下测试)

# example of use:
a_hash = {user_info: {type: "query_service", e_mail: "my@email.com", phone: "+79876543322"}, cars_makers: ["bmw", "mitsubishi"], car_models: [bmw: {model: "1er", year_mfc: 2006}, mitsubishi: {model: "pajero", year_mfc: 1997}]}
pretty_html = a_hash.pretty_html

# include this module to your libs:
module MyPrettyPrint
    def pretty_html indent = 0
        result = ""
        if self.class == Hash
            self.each do |key, value|
                result += "#{key}: #{[Array, Hash].include?(value.class) ? value.pretty_html(indent+1) : value}"
            end
        elsif self.class == Array
            result = "[#{self.join(', ')}]"
        end
        "#{result}"
    end

end

class Hash
    include MyPrettyPrint
end

class Array
    include MyPrettyPrint
end

使用pretty_generate()函数，该函数内置于JSON的后期版本中。例如:

require 'json'
my_object = { :array => [1, 2, 3, { :sample => "hash"} ], :foo => "bar" }
puts JSON.pretty_generate(my_object)

这就得到了:

{
  "array": [
    1,
    2,
    3,
    {
      "sample": "hash"
    }
  ],
  "foo": "bar"
}

漂亮的打印变体(Rails):

my_obj = {
  'array' => [1, 2, 3, { "sample" => "hash"}, 44455, 677778, nil ],
  foo: "bar", rrr: {"pid": 63, "state with nil and \"nil\"": false},
  wwww: 'w' * 74
}

require 'pp'
puts my_obj.as_json.pretty_inspect.
            gsub('=>', ': ').
            gsub(/"(?:[^"\\]|\\.)*"|\bnil\b/) {|m| m == 'nil' ? 'null' : m }.
            gsub(/\s+$/, "")

结果:

{"array": [1, 2, 3, {"sample": "hash"}, 44455, 677778, null],
 "foo": "bar",
 "rrr": {"pid": 63, "state with nil and \"nil\"": false},
 "wwww":
  "wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww"}

HTML中的<pre>标记，与JSON一起使用。pretty_generate，将在视图中漂亮地呈现JSON。当我杰出的老板给我看这个时，我非常高兴:

<% if @data.present? %>
   <pre><%= JSON.pretty_generate(@data) %></pre>
<% end %>

我能想到的最简单的例子:

my_json = '{ "name":"John", "age":30, "car":null }'
puts JSON.pretty_generate(JSON.parse(my_json))

Rails控制台示例:

core dev 1555:0> my_json = '{ "name":"John", "age":30, "car":null }'
=> "{ \"name\":\"John\", \"age\":30, \"car\":null }"
core dev 1556:0> puts JSON.pretty_generate(JSON.parse(my_json))
{
  "name": "John",
  "age": 30,
  "car": null
}
=> nil