How to pretty format JSON output in Ruby on Rails

Question

I would like my JSON output in Ruby on Rails to be  pretty  or nicely formatted    Right now  I call to json and my JSON is all on one line   At times this can be difficult to see if there is a problem in the JSON output stream   Is there way to configure to make my JSON  pretty  or nicely formatted in Rails

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Dumping an ActiveRecord object to JSON  in the Rails console    pp User first as json      gt      id    gt  1    first name    gt   Polar     last name    gt   Bear

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I use the following as I find the headers  status and JSON output useful as a set  The call routine is broken out on recommendation from a railscasts presentation at  http   railscasts com episodes 151-rack-middleware autoplay true    class LogJson    def initialize app       app   app   end    def call env      dup  call env    end    def  call env       status   headers   response    app call env        status   headers  self    end    def each  amp block      if  headers  Content-Type        application  json        obj   JSON parse  response body        pretty str   JSON pretty unparse obj         headers  Content-Length     Rack  Utils bytesize pretty str  to s       Rails logger info   HTTP Headers       headers            Rails logger info   HTTP Status       status            Rails logger info   JSON Response      pretty str         end       response each  amp block    end   end

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Use the pretty generate   function  built into later versions of JSON  For example   require  json  my object      array   gt   1  2  3     sample   gt   hash       foo   gt   bar    puts JSON pretty generate my object    Which gets you        array         1      2      3               sample    hash                foo    bar

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Here is a middleware solution modified from this excellent answer by  gertas   This solution is not Rails specific--it should work with any Rack application   The middleware technique used here  using  each  is explained at ASCIIcasts 151  Rack Middleware by Eifion Bedford   This code goes in app middleware pretty json response rb   class PrettyJsonResponse    def initialize app       app   app   end    def call env       status   headers   response    app call env        status   headers  self    end    def each  amp block       response each do  body        if  headers  Content-Type        application  json          body   pretty print body        end       block call body      end   end    private    def pretty print json      obj   JSON parse json        JSON pretty unparse obj    end  end   To turn it on  add this to config environments test rb and config environments development rb   config middleware use  PrettyJsonResponse    As  gertas warns in his version of this solution  avoid using it in production   It s somewhat slow   Tested with Rails 4 1 6

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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

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If you are using RABL you can configure it as described here to use JSON pretty generate   class PrettyJson   def self dump object      JSON pretty generate object    indent   gt           end end  Rabl configure do  config          config json engine   PrettyJson if Rails env development        end   A problem with using JSON pretty generate is that JSON schema validators will no longer be happy with your datetime strings  You can fix those in your config initializers rabl config rb with   ActiveSupport  TimeWithZone class eval do   alias method  orig to s   to s   def to s format    default      format     default   iso8601   orig to s format    end end

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Using  lt pre gt  HTML code and pretty generate is good trick    lt     require  json     hash   JSON  hey   test   num    one  1  two  2  threes    three  3  tthree  33      to json     gt    lt pre gt     lt     JSON pretty generate hash    gt   lt  pre gt

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If you re looking to quickly implement this in a Rails controller action to send a JSON response   def index   my json       key    value       render json  JSON pretty generate  JSON parse my json   end

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Here is a middleware solution modified from this excellent answer by  gertas   This solution is not Rails specific--it should work with any Rack application   The middleware technique used here  using  each  is explained at ASCIIcasts 151  Rack Middleware by Eifion Bedford   This code goes in app middleware pretty json response rb   class PrettyJsonResponse    def initialize app       app   app   end    def call env       status   headers   response    app call env        status   headers  self    end    def each  amp block       response each do  body        if  headers  Content-Type        application  json          body   pretty print body        end       block call body      end   end    private    def pretty print json      obj   JSON parse json        JSON pretty unparse obj    end  end   To turn it on  add this to config environments test rb and config environments development rb   config middleware use  PrettyJsonResponse    As  gertas warns in his version of this solution  avoid using it in production   It s somewhat slow   Tested with Rails 4 1 6

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If you re looking to quickly implement this in a Rails controller action to send a JSON response   def index   my json       key    value       render json  JSON pretty generate  JSON parse my json   end

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Check out Awesome Print   Parse the JSON string into a Ruby Hash  then display it with ap like so   require  awesome print  require  json   json      holy     nested    json     batman      a   1   b   2     ap JSON parse json     With the above  you ll see        holy    gt         0   nested        1   json          batman     gt         a    gt  1       b    gt  2         Awesome Print will also add some color that Stack Overflow won t show you

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At Controller def branch      data   Model all     render json  JSON pretty generate  data as json  end

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Use the pretty generate   function  built into later versions of JSON  For example   require  json  my object      array   gt   1  2  3     sample   gt   hash       foo   gt   bar    puts JSON pretty generate my object    Which gets you        array         1      2      3               sample    hash                foo    bar

User · Answer

If you are using RABL you can configure it as described here to use JSON pretty generate   class PrettyJson   def self dump object      JSON pretty generate object    indent   gt           end end  Rabl configure do  config          config json engine   PrettyJson if Rails env development        end   A problem with using JSON pretty generate is that JSON schema validators will no longer be happy with your datetime strings  You can fix those in your config initializers rabl config rb with   ActiveSupport  TimeWithZone class eval do   alias method  orig to s   to s   def to s format    default      format     default   iso8601   orig to s format    end end

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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

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I have used the gem CodeRay and it works pretty well  The format includes colors and it recognises a lot of different formats   I have used it on a gem that can be used for debugging rails APIs and it works pretty well   By the way  the gem is named  api explorer   http   www github com toptierlabs api explorer

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If you want to    Prettify all outgoing JSON responses from your app automatically  Avoid polluting Object to json  as json Avoid parsing re-rendering JSON using middleware  YUCK   Do it the RAILS WAY    Then     replace the ActionController  Renderer for JSON  Just add the following code to your ApplicationController   ActionController  Renderers add  json do  json  options    unless json kind of  String      json   json as json options  if json respond to   as json      json   JSON pretty generate json  options    end    if options  callback  present      self content type     Mime  JS        options  callback     json      else     self content type     Mime  JSON     json   end end

User · Answer

I use the following as I find the headers  status and JSON output useful as a set  The call routine is broken out on recommendation from a railscasts presentation at  http   railscasts com episodes 151-rack-middleware autoplay true    class LogJson    def initialize app       app   app   end    def call env      dup  call env    end    def  call env       status   headers   response    app call env        status   headers  self    end    def each  amp block      if  headers  Content-Type        application  json        obj   JSON parse  response body        pretty str   JSON pretty unparse obj         headers  Content-Length     Rack  Utils bytesize pretty str  to s       Rails logger info   HTTP Headers       headers            Rails logger info   HTTP Status       status            Rails logger info   JSON Response      pretty str         end       response each  amp block    end   end

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At Controller def branch      data   Model all     render json  JSON pretty generate  data as json  end

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Here s my solution which I derived from other posts during my own search   This allows you to send the pp and jj output to a file as needed   require  pp  require  json   class File   def pp  objs      objs each   obj        PP pp obj  self            objs size  lt   1   objs first   objs   end   def jj  objs      objs each   obj        obj   JSON parse obj to json        self puts JSON pretty generate obj            objs size  lt   1   objs first   objs   end end  test object      name   gt    first   Christopher   last   Mullins      grades   gt     English    gt   B     Algebra    gt   A        test json object   JSON parse test object to json   File open  log object dump txt    w   do  file    file pp test object  end  File open  log json dump txt    w   do  file    file jj test json object  end

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If you  find that the pretty generate option built into Ruby s JSON library is not  pretty  enough  I recommend my own NeatJSON gem for your formatting   To use it   gem install neatjson   and then use  JSON neat generate   instead of  JSON pretty generate   Like Ruby s pp it will keep objects and arrays on one line when they fit  but wrap to multiple as needed  For example        navigation createroute poi          text   Lay in a course to the Hilton   params    poi   Hilton           text   Take me to the airport   params    poi   airport           text   Let s go to IHOP   params    poi   IHOP           text   Show me how to get to The Med   params    poi   The Med           text   Create a route to Arby s   params    poi   Arby s                  text   Go to the Hilton by the Airport          params    poi   Hilton   location   Airport                       text   Take me to the Fry s in Fresno          params    poi   Fry s   location   Fresno                 navigation eta          text   When will we get there           text   When will I arrive           text   What time will I get to the destination           text   What time will I reach the destination           text   What time will it be when I arrive            It also supports a variety of formatting options to further customize your output  For example  how many spaces before after colons  Before after commas  Inside the brackets of arrays and objects  Do you want to sort the keys of your object  Do you want the colons to all be lined up

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Pretty print variant   my object      array   gt   1  2  3     sample   gt   hash    44455  677778  9900     foo   gt   bar   rrr    pid   63   state   false   puts my object as json pretty inspect gsub    gt            Result     array    1  2  3    sample    hash    44455  677778  9900     foo    bar     rrr     pid   63   state   false

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Pretty print variant   my object      array   gt   1  2  3     sample   gt   hash    44455  677778  9900     foo   gt   bar   rrr    pid   63   state   false   puts my object as json pretty inspect gsub    gt            Result     array    1  2  3    sample    hash    44455  677778  9900     foo    bar     rrr     pid   63   state   false

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Thanks to Rack Middleware and Rails 3 you can output pretty JSON for every request without changing any controller of your app  I have written such middleware snippet and I get nicely printed JSON in browser and curl output   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   The above code should be placed in app middleware pretty json response rb of your Rails project  And the final step is to register the middleware in config environments development rb   config middleware use PrettyJsonResponse   I don t recommend to use it in production rb  The JSON reparsing may degrade response time and throughput of your production app  Eventually extra logic such as  X-Pretty-Json  true  header may be introduced to trigger formatting for manual curl requests on demand    Tested with Rails 3 2 8-5 0 0  Ruby 1 9 3-2 2 0  Linux

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Simplest example  I could think of   my json       name   John    age  30   car  null    puts JSON pretty generate JSON parse my json     Rails console example   core dev 1555 0 gt  my json       name   John    age  30   car  null      gt       name     John      age   30    car   null    core dev 1556 0 gt  puts JSON pretty generate JSON parse my json        name    John      age   30     car   null     gt  nil

User · Answer

Check out Awesome Print   Parse the JSON string into a Ruby Hash  then display it with ap like so   require  awesome print  require  json   json      holy     nested    json     batman      a   1   b   2     ap JSON parse json     With the above  you ll see        holy    gt         0   nested        1   json          batman     gt         a    gt  1       b    gt  2         Awesome Print will also add some color that Stack Overflow won t show you

User · Answer

Dumping an ActiveRecord object to JSON  in the Rails console    pp User first as json      gt      id    gt  1    first name    gt   Polar     last name    gt   Bear

User · Answer

Simplest example  I could think of   my json       name   John    age  30   car  null    puts JSON pretty generate JSON parse my json     Rails console example   core dev 1555 0 gt  my json       name   John    age  30   car  null      gt       name     John      age   30    car   null    core dev 1556 0 gt  puts JSON pretty generate JSON parse my json        name    John      age   30     car   null     gt  nil

User · Answer

If you  find that the pretty generate option built into Ruby s JSON library is not  pretty  enough  I recommend my own NeatJSON gem for your formatting   To use it   gem install neatjson   and then use  JSON neat generate   instead of  JSON pretty generate   Like Ruby s pp it will keep objects and arrays on one line when they fit  but wrap to multiple as needed  For example        navigation createroute poi          text   Lay in a course to the Hilton   params    poi   Hilton           text   Take me to the airport   params    poi   airport           text   Let s go to IHOP   params    poi   IHOP           text   Show me how to get to The Med   params    poi   The Med           text   Create a route to Arby s   params    poi   Arby s                  text   Go to the Hilton by the Airport          params    poi   Hilton   location   Airport                       text   Take me to the Fry s in Fresno          params    poi   Fry s   location   Fresno                 navigation eta          text   When will we get there           text   When will I arrive           text   What time will I get to the destination           text   What time will I reach the destination           text   What time will it be when I arrive            It also supports a variety of formatting options to further customize your output  For example  how many spaces before after colons  Before after commas  Inside the brackets of arrays and objects  Do you want to sort the keys of your object  Do you want the colons to all be lined up

User · Answer

If you want to    Prettify all outgoing JSON responses from your app automatically  Avoid polluting Object to json  as json Avoid parsing re-rendering JSON using middleware  YUCK   Do it the RAILS WAY    Then     replace the ActionController  Renderer for JSON  Just add the following code to your ApplicationController   ActionController  Renderers add  json do  json  options    unless json kind of  String      json   json as json options  if json respond to   as json      json   JSON pretty generate json  options    end    if options  callback  present      self content type     Mime  JS        options  callback     json      else     self content type     Mime  JSON     json   end end

User · Answer

Here s my solution which I derived from other posts during my own search   This allows you to send the pp and jj output to a file as needed   require  pp  require  json   class File   def pp  objs      objs each   obj        PP pp obj  self            objs size  lt   1   objs first   objs   end   def jj  objs      objs each   obj        obj   JSON parse obj to json        self puts JSON pretty generate obj            objs size  lt   1   objs first   objs   end end  test object      name   gt    first   Christopher   last   Mullins      grades   gt     English    gt   B     Algebra    gt   A        test json object   JSON parse test object to json   File open  log object dump txt    w   do  file    file pp test object  end  File open  log json dump txt    w   do  file    file jj test json object  end

User · Answer

Using  lt pre gt  HTML code and pretty generate is good trick    lt     require  json     hash   JSON  hey   test   num    one  1  two  2  threes    three  3  tthree  33      to json     gt    lt pre gt     lt     JSON pretty generate hash    gt   lt  pre gt

User · Answer

Thanks to Rack Middleware and Rails 3 you can output pretty JSON for every request without changing any controller of your app  I have written such middleware snippet and I get nicely printed JSON in browser and curl output   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   The above code should be placed in app middleware pretty json response rb of your Rails project  And the final step is to register the middleware in config environments development rb   config middleware use PrettyJsonResponse   I don t recommend to use it in production rb  The JSON reparsing may degrade response time and throughput of your production app  Eventually extra logic such as  X-Pretty-Json  true  header may be introduced to trigger formatting for manual curl requests on demand    Tested with Rails 3 2 8-5 0 0  Ruby 1 9 3-2 2 0  Linux

User · Answer

The  lt pre gt  tag in HTML  used with JSON pretty generate  will render the JSON pretty in your view  I was so happy when my illustrious boss showed me this    lt   if  data present    gt      lt pre gt  lt    JSON pretty generate  data    gt  lt  pre gt   lt   end   gt

User · Answer

I have used the gem CodeRay and it works pretty well  The format includes colors and it recognises a lot of different formats   I have used it on a gem that can be used for debugging rails APIs and it works pretty well   By the way  the gem is named  api explorer   http   www github com toptierlabs api explorer

User · Answer

The  lt pre gt  tag in HTML  used with JSON pretty generate  will render the JSON pretty in your view  I was so happy when my illustrious boss showed me this    lt   if  data present    gt      lt pre gt  lt    JSON pretty generate  data    gt  lt  pre gt   lt   end   gt

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