How should I escape strings in JSON

Question

When creating JSON data manually  how should I escape string fields  Should I use something like Apache Commons Lang s StringEscapeUtilities escapeHtml  StringEscapeUtilities escapeXml  or should I use java net URLEncoder   The problem is that when I use SEU escapeHtml  it doesn t escape quotes and when I wrap the whole string in a pair of  s  a malformed JSON will be generated

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Extract From Jettison    public static String quote String string             if  string    null    string length      0                 return                              char         c   0           int          i           int          len   string length             StringBuilder sb   new StringBuilder len   4            String       t            sb append                for  i   0  i  lt  len  i    1                 c   string charAt i                switch  c                 case                    case                       sb append                         sb append c                    break               case                         if  b      lt                           sb append                                              sb append c                    break               case   b                    sb append    b                     break               case   t                    sb append    t                     break               case   n                    sb append    n                     break               case   f                    sb append    f                     break               case   r                   sb append    r                    break               default                   if  c  lt                              t    000    Integer toHexString c                        sb append    u    t substring t length   - 4                       else                        sb append c                                                         sb append                return sb toString

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Apache commons-text now has a  StringEscapeUtils escapeJson String

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org json simple JSONObject escape   escapes quotes        r   n   b   f   t and other control characters  It can be used to escape JavaScript codes   import org json simple JSONObject  String test    JSONObject escape  your string

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Try this org codehaus jettison json JSONObject quote  your string     Download it here  http   mvnrepository com artifact org codehaus jettison jettison

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using the  uXXXX syntax can solve this problem  google UTF-16 with the name of the sign  you can find out XXXX  for example utf-16 double quote

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I have not spent the time to make 100  certain  but it worked for my inputs enough to be accepted by online JSON validators   org apache velocity tools generic EscapeTool EscapeTool   java  input     although it does not look any better than org codehaus jettison json JSONObject quote  your string     I simply use velocity tools in my project already - my  manual JSON  building was within a velocity template

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StringEscapeUtils escapeJavaScript   StringEscapeUtils escapeEcmaScript should do the trick too

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Ideally  find a JSON library in your language that you can feed some appropriate data structure to  and let it worry about how to escape things  It ll keep you much saner  If for whatever reason you don t have a library in your language  you don t want to use one  I wouldn t suggest this     or you re writing a JSON library  read on   Escape it according to the RFC  JSON is pretty liberal  The only characters you must escape are       and control codes  anything less than U 0020    This structure of escaping is specific to JSON  You ll need a JSON specific function  All of the escapes can be written as  uXXXX where XXXX is the UTF-16 code unit   for that character  There are a few shortcuts  such as     which work as well   And they result in a smaller and clearer output    For full details  see the RFC     JSON s escaping is built on JS  so it uses  uXXXX  where XXXX is a UTF-16 code unit  For code points outside the BMP  this means encoding surrogate pairs  which can get a bit hairy   Or  you can just output the character directly  since JSON s encoded for is Unicode text  and allows these particular characters

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Consider Moshi s JsonWriter class  It has a wonderful API and it reduces copying to a minimum  everything can be nicely streamed to a filed  OutputStream  etc   OutputStream os        JsonWriter json   new JsonWriter Okio buffer Okio sink os     json beginObject    json name  id   value getId     json name  scores    json beginArray    for  Double score   getScores        json value score     json endArray    json endObject      If you want the string in hand   Buffer b   new Buffer       okio Buffer JsonWriter writer   new JsonWriter b         String jsonString   b readUtf8

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Not sure what you mean by  creating json manually   but you can use something like gson  http   code google com p google-gson    and that would transform your HashMap  Array  String  etc  to a JSON value  I recommend going with a framework for this

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org json JSONObject quote String data  method does the job  import org json JSONObject  String jsonEncodedString   JSONObject quote data     Extract from the documentation      Encodes data as a JSON string  This applies quotes and any necessary character escaping        Null will be interpreted as an empty string

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If you need to escape JSON inside JSON string  use org json JSONObject quote  your json string that needs to be escaped   seem to work well

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For those who came here looking for a command-line solution  like me  cURL s --data-urlencode works fine   curl -G -v -s --data-urlencode  query   type      music artist     https   www googleapis com freebase v1 mqlread    sends  GET  freebase v1 mqlread query  7B 22type 22 20 3A 20 22 2Fmusic 2Fartist 22 7D HTTP 1 1     for example  Larger JSON data can be put in a file and you d use the   syntax to specify a file to slurp in the to-be-escaped data from  For example  if    cat 1 json         type     music artist       name    The Police       album          you d use  curl -G -v -s --data-urlencode query 1 json  https   www googleapis com freebase v1 mqlread    And now  this is also a tutorial on how to query Freebase from the command line  -

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Use EscapeUtils class in commons lang API   EscapeUtils escapeJavaScript  Your JSON string

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The methods here that show the actual implementation are all faulty   I don t have Java code  but just for the record  you could easily convert this C -code   Courtesy of the mono-project    https   github com mono mono blob master mcs class System Web System Web HttpUtility cs  public static string JavaScriptStringEncode string value  bool addDoubleQuotes        if  string IsNullOrEmpty value           return addDoubleQuotes            string Empty       int len   value Length      bool needEncode   false      char c      for  int i   0  i  lt  len  i                  c   value i            if  c  gt   0  amp  amp  c  lt   31    c    34    c    39    c    60    c    62    c    92                        needEncode   true              break                       if   needEncode          return addDoubleQuotes          value          value       var sb   new System Text StringBuilder        if  addDoubleQuotes          sb Append            for  int i   0  i  lt  len  i                  c   value i           if  c  gt   0  amp  amp  c  lt   7    c    11    c  gt   14  amp  amp  c  lt   31    c    39    c    60    c    62              sb AppendFormat    u 0 x4     int c           else switch   int c                                case 8                      sb Append    b                        break                   case 9                      sb Append    t                        break                   case 10                      sb Append    n                        break                   case 12                      sb Append    f                        break                   case 13                      sb Append    r                        break                   case 34                      sb Append                              break                   case 92                      sb Append                              break                   default                      sb Append c                       break                           if  addDoubleQuotes          sb Append            return sb ToString        This can be compacted into          https   github com mono mono blob master mcs class System Json System Json JsonValue cs public class SimpleJSON        private static  bool NeedEscape string src  int i                char c   src i           return c  lt  32    c           c                        Broken lead surrogate                 c  gt     uD800   amp  amp  c  lt     uDBFF   amp  amp                   i    src Length - 1    src i   1   lt    uDC00     src i   1   gt    uDFFF                   Broken tail surrogate                 c  gt     uDC00   amp  amp  c  lt     uDFFF   amp  amp                   i    0    src i - 1   lt    uD800     src i - 1   gt    uDBFF                   To produce valid JavaScript                c      u2028     c      u2029                 Escape   lt    for  lt script gt  tags                 c         amp  amp  i  gt  0  amp  amp  src i - 1       lt                  public static string EscapeString string src                System Text StringBuilder sb   new System Text StringBuilder             int start   0          for  int i   0  i  lt  src Length  i                if  NeedEscape src  i                                 sb Append src  start  i - start                   switch  src i                                         case   b   sb Append    b    break                      case   f   sb Append    f    break                      case   n   sb Append    n    break                      case   r   sb Append    r    break                      case   t   sb Append    t    break                      case       sb Append          break                      case       sb Append          break                      case      sb Append         break                      default                          sb Append    u                            sb Append   int src i   ToString  x04                             break                                    start   i   1                        sb Append src  start  src Length - start           return sb ToString

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Apache commons lang now supports this   Just make sure you have a recent enough version of Apache commons lang on your classpath   You ll need version 3 2   Release Notes for version 3 2  LANG-797   Added escape unescapeJson to StringEscapeUtils

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I think the best answer in 2017 is to use the javax json APIs   Use javax json JsonBuilderFactory to create your json objects  then write the objects out using javax json JsonWriterFactory   Very nice builder writer combination

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If you are using fastexml jackson  you can use the following  com fasterxml jackson core io JsonStringEncoder getInstance   quoteAsString input   If you are using codehaus jackson  you can use the following  org codehaus jackson io JsonStringEncoder getInstance   quoteAsString input

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