How to copy bytes in JSONArray to Byte array

Question

I am getting image data in the form of buffer(bytes), but I want to convert it into a base64 string. The data is received inside a JSONArray, like so

JSONArray : `[53,57,51,47,53,57,51,55,50,98,98,54,53,51,54,97,102,101,53,101,102,54,57,54,53,54,53,51,102,98,53,99,98,98,99,51,98,48,52,57,56,52,52,101,54,48,50,99,56,55,101,54,53,97,51,102,56,49,56,57,56,98,102,56,49,57,97,57]`

For that I am copying the JSONArray into "byte" array, like so :

JSONArray bytearray_json = record.getJSONObject("image").getJSONArray("data");
byte[] bytes = new byte[bytearray_json.length()];
for (int i =0; i < bytearray_json.length(); i++ ) {
    bytes[i] = (byte)bytearray_json.get(i);
}
String base_64 = Base64.encodeToString(bytes,Base64.DEFAULT);

But I get an exception : Cannot cast Integer to byte I cannot do bytearray_json.get(i).toString().getBytes(); since it returns a Byte Array.

How can I solve this?

Try bytes[i] = (byte)(int)bytearray_json.get(i).

user4910279
– user4910279

2017-07-16 13:06:52 +00:00
Commented Jul 16, 2017 at 13:06 — user4910279
– user4910279, Commented Jul 16, 2017 at 13:06

Hasangi · Accepted Answer · 2018-01-20 07:50:51Z

5

You can try this out to,

JSONArray jsonArray = response.getJSONObject("image").getJSONArray("data");
byte[] bytes = new byte[jsonArray.length()];
for (int i = 0; i < jsonArray.length(); i++) {
        bytes[i]=(byte)(((int)jsonArray.get(i)) & 0xFF);
}
 Base64.encodeToString(bytes, Base64.DEFAULT);

answered Jan 20, 2018 at 7:50

Hasangi

3208 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Yusril Maulidan Raji Over a year ago

would you like to elaborate why it needs & 0xFF ?

Hasangi Over a year ago

Well, there are mainly two reasons to use this & 0xFF, 1. To mask the value to get only last 8 bits, and ignores all the rest of the bits. 2. In this case, we are trying to deal with RGB values which is exactly 8 bits long. You can read more on

Oz Shabat · Accepted Answer · 2020-12-24 09:25:23Z

0

Thanks @Hasangi for your answer.

For those of you who wants to use a more modern answer, based on Kotlin:

fun JSONArray.toByteArray(): ByteArray {
    val byteArr = ByteArray(length())
    for (i in 0 until length()) {
        byteArr[i] = (get(i) as Int and 0xFF).toByte()
    }
    return byteArr
}

and to use:

val bytes = jsonObj.getJSONArray("bytes").toByteArray()

answered Dec 24, 2020 at 9:25

Oz Shabat

1,65218 silver badges18 bronze badges

Collectives™ on Stack Overflow

How to copy bytes in JSONArray to Byte array

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related