How can I pretty-print JSON using Go

Question

Does anyone know of a simple way to pretty-print JSON output in Go   The stock http   golang org pkg encoding json  package does not seem to include functionality for this  EDIT  it does  see accepted answer  and a quick google doesn t turn up anything obvious   Uses I m looking for are both pretty-printing the result of json Marshal and just formatting a string full of JSON from wherever  so it s easier to read for debug purposes

User · Answer

package cube  import        encoding json       fmt       github com magiconair properties assert       k8s io api rbac v1beta1      v1  k8s io apimachinery pkg apis meta v1       testing     func TestRole t  testing T         clusterRoleBind     amp v1beta1 ClusterRoleBinding          ObjectMeta  v1 ObjectMeta              Name   serviceaccounts-cluster-admin                      RoleRef  v1beta1 RoleRef              APIGroup   rbac authorization k8s io               Kind       ClusterRole               Name       cluster-admin                      Subjects    v1beta1 Subject               Kind       Group               APIGroup   rbac authorization k8s io               Name       system serviceaccounts                                   b  err    json MarshalIndent clusterRoleBind                assert Equal t  nil  err      fmt Println string b

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Here is my solution   import        bytes       encoding json     const       empty          tab       t     func PrettyJson data interface     string  error        buffer    new bytes Buffer      encoder    json NewEncoder buffer      encoder SetIndent empty  tab       err    encoder Encode data      if err    nil          return empty  err           return buffer String    nil

User · Answer

Here s what I use  If it fails to pretty print the JSON it just returns the original string  Useful for printing HTTP responses that should contain JSON   import        encoding json       bytes     func jsonPrettyPrint in string  string       var out bytes Buffer     err    json Indent  amp out    byte in         t       if err    nil           return in           return out String

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i am sort of new to go  but this is what i gathered up so far   package srf  import        bytes       encoding json       os     func WriteDataToFileAsJSON data interface    filedir string   int  error          write data as buffer to json encoder     buffer    new bytes Buffer      encoder    json NewEncoder buffer      encoder SetIndent       t        err    encoder Encode data      if err    nil           return 0  err           file  err    os OpenFile filedir  os O RDWR os O CREATE  0755      if err    nil           return 0  err           n  err    file Write buffer Bytes        if err    nil           return 0  err           return n  nil     This is the execution of the function  and just standard  b       json MarshalIndent SomeType        t     Code   package main  import        encoding json       fmt       io ioutil       log       minerals    minerals      srf    srf     func main            array of Test struct     var SomeType  10 minerals Test        Create 10 units of some random data to write     for a    0  a  lt  10  a             SomeType a    minerals Test              Name     Rand               Id      123              A        desc               Num     999              Link     somelink               People    string  John Doe    Aby Daby                           writes aditional data to existing file  or creates a new file     n  err    srf WriteDataToFileAsJSON SomeType   test2 json       if err    nil           log Fatal err            fmt Println  srf printed    n    bytes to     test2 json          overrides previous file     b       json MarshalIndent SomeType        t       ioutil WriteFile  test json   b  0644

User · Answer

By pretty-print  I assume you mean indented  like so         data   1234     rather than    data  1234    The easiest way to do this is with MarshalIndent  which will let you specify how you would like it indented via the indent argument  Thus  json MarshalIndent data              will pretty-print using four spaces for indentation

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I was frustrated by the lack of a fast  high quality way to marshal JSON to a colorized string in Go so I wrote my own Marshaller called ColorJSON   With it  you can easily produce output like this using very little code     package main  import        fmt       encoding json        github com TylerBrock colorjson     func main         str              str    foo          num   100         bool   false         null   null         array     foo    bar    baz           obj      a   1   b   2               var obj map string interface       json Unmarshal   byte str    amp obj          Make a custom formatter with indent set     f    colorjson NewFormatter       f Indent   4         Marshall the Colorized JSON     s       f Marshal obj      fmt Println string s       I m writing the documentation for it now but I was excited to share my solution

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For better memory usage  I guess this is better   var out io Writer enc    json NewEncoder out  enc SetIndent             if err    enc Encode data   err    nil       panic err

User · Answer

Edit Looking back  this is non-idiomatic Go  Small helper functions like this add an extra step of complexity  In general  the Go philosophy prefers to include the 3 simple lines over 1 tricky line     As  robyoder mentioned  json Indent is the way to go  Thought I d add this small prettyprint function   package main  import        bytes       encoding json       fmt       dont do this  see above edit func prettyprint b   byte     byte  error        var out bytes Buffer     err    json Indent  amp out  b                return out Bytes    err    func main         b      byte    hello    123         b      prettyprint b      fmt Printf   s   b      https   go-sandbox com   R4LWpkkHIN or http   play golang org p R4LWpkkHIN

User · Answer

You can do it with json MarshalIndent data             package main  import     fmt     encoding json    Import package      Create struct type Users struct       ID   int     NAME string      Asign struct var user   Users func main        Append data to variable user  user   append user  Users 1   Saturn Rings       Use json package the blank spaces are for the indent  data       json MarshalIndent user               Print json formatted  fmt Println string data

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The accepted answer is great if you have an object you want to turn into JSON  The question also mentions pretty-printing just any JSON string  and that s what I was trying to do  I just wanted to pretty-log some JSON from a POST request  specifically a CSP violation report     To use MarshalIndent  you would have to Unmarshal that into an object  If you need that  go for it  but I didn t  If you just need to pretty-print a byte array  plain Indent is your friend   Here s what I ended up with   import        bytes       encoding json       log       net http     func HandleCSPViolationRequest w http ResponseWriter  req  http Request        body    App MustReadBody req  w      if body    nil           return            var prettyJSON bytes Buffer     error    json Indent  amp prettyJSON  body        t       if error    nil           log Println  JSON parse error     error          App BadRequest w          return            log Println  CSP Violation    string prettyJSON Bytes

User · Answer

A simple off the shelf pretty printer in Go  One can compile it to a binary through   go build -o jsonformat jsonformat go   It reads from standard input  writes to standard output and allow to set indentation   package main  import        bytes       encoding json       flag       fmt       io ioutil       os     func main         indent    flag String  indent          indentation string character for formatter       flag Parse       src  err    ioutil ReadAll os Stdin      if err    nil           fmt Fprintf os Stderr   problem reading   s   err          os Exit 1             dst     amp bytes Buffer       if err    json Indent dst  src       indent   err    nil           fmt Fprintf os Stderr   problem formatting   s   err          os Exit 1            if    err   dst WriteTo os Stdout   err    nil           fmt Fprintf os Stderr   problem writing   s   err          os Exit 1            It allows to run a bash commands like   cat myfile   jsonformat   grep  key

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