Put byte array to JSON and vice versa

Question

Is it possible to put a byte    byte array  to JSON   if so  how can I do that in java  then read that JSON and convert that field again to byte

User · Answer

The typical way to send binary in json is to base64 encode it.

Java provides different ways to Base64 encode and decode a byte[]. One of these is DatatypeConverter.

Very simply

byte[] originalBytes = new byte[] { 1, 2, 3, 4, 5};
String base64Encoded = DatatypeConverter.printBase64Binary(originalBytes);
byte[] base64Decoded = DatatypeConverter.parseBase64Binary(base64Encoded);

You'll have to make this conversion depending on the json parser/generator library you use.

User · Answer

Amazingly now org json now lets you put a byte   object directly into a json and it remains readable  you can even send the resulting object over a websocket and it will be readable on the other side  but i am not sure yet if the size of the resulting object is bigger or smaller than if you were converting your byte array to base64  it would certainly be neat if it was smaller   It seems to be incredibly hard to measure how much space such a json  object takes up in java  if your json consists merely of strings it is easily achievable by simply stringifying it but with a bytearray inside it i fear it is not as straightforward    stringifying our json in java replaces my bytearray for a 10 character string that looks like an id  doing the same in node js replaces our byte   for an unquoted value reading  lt Buffered Array  f0 ff ff     gt  the length of the latter indicates a size increase of  300  as would be expected

User · Answer

Here is a good example of base64 encoding byte arrays  It gets more complicated when you throw unicode characters in the mix to send things like PDF documents  After encoding a byte array the encoded string can be used as a JSON property value   Apache commons offers good utilities    byte   bytes   getByteArr     String base64String   Base64 encodeBase64String bytes    byte   backToBytes   Base64 decodeBase64 base64String     https   developer mozilla org en-US docs Web JavaScript Base64 encoding and decoding  Java server side example   public String getUnsecureContentBase64 String url          throws ClientProtocolException  IOException                  getUnsecureContent will generate some byte       byte   result   getUnsecureContent url                   use apache org apache commons codec binary Base64                if you re sending back as a http request result you may have to                org apache commons httpclient util URIUtil encodeQuery     return Base64 encodeBase64String result       JavaScript decode     decode URL encoding if encoded before returning result var uriEncodedString   decodeURIComponent response    var byteArr   base64DecToArr uriEncodedString      from mozilla function b64ToUint6  nChr       return nChr  gt  64  amp  amp  nChr  lt  91         nChr - 65       nChr  gt  96  amp  amp  nChr  lt  123         nChr - 71       nChr  gt  47  amp  amp  nChr  lt  58         nChr   4       nChr     43         62       nChr     47         63             0      function base64DecToArr  sBase64  nBlocksSize       var     sB64Enc   sBase64 replace    A-Za-z0-9      g       nInLen   sB64Enc length      nOutLen   nBlocksSize   Math ceil  nInLen   3   1  gt  gt  2    nBlocksSize    nBlocksSize   nInLen   3   1  gt  gt  2  taBytes   new Uint8Array nOutLen      for  var nMod3  nMod4  nUint24   0  nOutIdx   0  nInIdx   0  nInIdx  lt  nInLen  nInIdx          nMod4   nInIdx  amp  3      nUint24    b64ToUint6 sB64Enc charCodeAt nInIdx    lt  lt  18 - 6   nMod4      if  nMod4     3    nInLen - nInIdx     1          for  nMod3   0  nMod3  lt  3  amp  amp  nOutIdx  lt  nOutLen  nMod3    nOutIdx              taBytes nOutIdx    nUint24  gt  gt  gt   16  gt  gt  gt  nMod3  amp  24   amp  255                nUint24   0                return taBytes

User · Answer

If your byte array may contain runs of ASCII characters that you d like to be able to see  you might prefer BAIS  Byte Array In String  format instead of Base64  The nice thing about BAIS is that if all the bytes happen to be ASCII  they are converted 1-to-1 to a string  e g  byte array  65 66 67  becomes simply  ABC   Also  BAIS often gives you a smaller file size than Base64  this isn t guaranteed    After converting the byte array to a BAIS string  write it to JSON like you would any other string   Here is a Java class  ported from the original C   that converts byte arrays to string and back   import java io    import java lang    import java util     public class ByteArrayInString        Encodes a byte array to a string with BAIS encoding  which       preserves runs of ASCII characters unchanged            For simplicity  this method s base-64 encoding always encodes groups of       three bytes if possible  as four characters   This decision may       unfortunately cut off the beginning of some ASCII runs    public static String convert byte   bytes    return convert bytes  true       public static String convert byte   bytes  boolean allowControlChars          StringBuilder sb   new StringBuilder        int i   0      int b      while  i  lt  bytes length              b   get bytes i           if  isAscii b  allowControlChars           sb append  char b         else           sb append   b               Do binary encoding in groups of 3 bytes         for     b   get bytes i                 int accum   b            System out println  i   i             if  i  lt  bytes length                b   get bytes i                 accum    accum  lt  lt  8    b              if  i  lt  bytes length                  b   get bytes i                   accum    accum  lt  lt  8    b                sb append encodeBase64Digit accum  gt  gt  18                  sb append encodeBase64Digit accum  gt  gt  12                  sb append encodeBase64Digit accum  gt  gt  6                  sb append encodeBase64Digit accum                  if  i  gt   bytes length                  break                else                 sb append encodeBase64Digit accum  gt  gt  10                  sb append encodeBase64Digit accum  gt  gt  4                  sb append encodeBase64Digit accum  lt  lt  2                  break                            else               sb append encodeBase64Digit accum  gt  gt  2                sb append encodeBase64Digit accum  lt  lt  4                break                        if  isAscii get bytes i   allowControlChars   amp  amp               i 1  gt   bytes length    isAscii get bytes i   allowControlChars    amp  amp               i 2  gt   bytes length    isAscii get bytes i   allowControlChars                  sb append          return to ASCII mode             break                                          return sb toString              Decodes a BAIS string back to a byte array    public static byte   convert String s          byte   b      try         b   s getBytes  UTF8          catch UnsupportedEncodingException e           throw new RuntimeException e getMessage               for  int i   0  i  lt  b length - 1    i          if  b i       b             int iOut   i             for                  int cur            if  i  gt   b length      cur   get b  i    lt  63    cur  gt  126               throw new RuntimeException  String cannot be interpreted as a BAIS array              int digit    cur - 64   amp  63            int zeros   16 - 6     number of 0 bits on right side of accum           int accum   digit  lt  lt  zeros             while    i  lt  b length                          if   cur   get b  i    lt  63    cur  gt  126                break              digit    cur - 64   amp  63              zeros -  6              accum    digit  lt  lt  zeros              if  zeros  lt   8                              b iOut       byte  accum  gt  gt  8                 accum  lt  lt   8                zeros    8                                       if   accum  amp  0xFF00     0     i  lt  b length  amp  amp  b i                       throw new RuntimeException  String cannot be interpreted as BAIS array              i                  Start taking bytes verbatim           while  i  lt  b length  amp  amp  b i       b               b iOut      b i               if  i  gt   b length              return Arrays copyOfRange b  0  iOut             i                                return b         static int get byte   bytes  int i    return   int bytes i    amp  0xFF       public static int decodeBase64Digit char digit        return digit  gt   63  amp  amp  digit  lt   126    digit - 64   amp  63   -1      public static char encodeBase64Digit int digit        return  char   digit   1  amp  63    63       static boolean isAscii int b  boolean allowControlChars        return b  lt  127  amp  amp   b  gt   32     allowControlChars  amp  amp  b      b           See also  C  unit tests

User · Answer

In line with  Qwertie s suggestion  but going further on the lazy side  you could just pretend that each byte is a ISO-8859-1 character  For the uninitiated  ISO-8859-1 is a single-byte encoding that matches the first 256 code points of Unicode  So  Ash s answer is actually redeemable with a charset  byte   args2   getByteArry    String byteStr   new String args2  Charset forName  quot ISO-8859-1 quot      This encoding has the same readability as BAIS  with the advantage that it is processed faster than either BAIS or base64 as less branching is required  It might look like the JSON parser is doing a bit more  but it s fine because dealing with non-ASCII by escaping or by UTF-8 is part of a JSON parser s job anyways  It could map better to some formats like MessagePack with a profile  Space-wise however  it is usually a loss  as nobody would be using UTF-16 for JSON  With UTF-8 each non-ASCII byte would occupy 2 bytes  while BAIS uses  2 4n   r  r 1  0  bytes for every run of 3n r such bytes  r is the remainder

User · Answer

what about simply this   byte   args2   getByteArry    String byteStr   new String args2

[java] Put byte array to JSON and vice versa

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