This post I will show you what I use to decode JWT to view the header and payload in Android.
I do not claim to be the owner writer of this code snippet. The main functions were gathered from searching various posts when I started my JWT journey and I am unable to find where it was from. When I find it, I will post the link.
I have altered the function to suit my needs.
Code
JWTUtils
object JWTUtils {
@Throws(Exception::class)
fun decoded(JWTEncoded: String) : MutableList<Any> {
try {
val arr = mutableListOf<Any>()
val split =
JWTEncoded.split("\\.".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
var s = getJson(split[0])
val header : JWTHeader = Gson().fromJson(s, JWTHeader::class.java)
arr.add(header)
s = getJson(split[1])
val body : JWTBody = Gson().fromJson(s, JWTBody::class.java)
arr.add(body)
//val header: JsonObject = JsonObject().getAsJsonObject(getJson(split[0]))
//val body: JsonObject = JsonObject().getAsJsonObject(getJson(split[1]))
//Log.d("JWT_DECODED", "Body: " + getJson(split[1]))
return arr
} catch (e: UnsupportedEncodingException) {
//Error
}
return mutableListOf()
}
private fun getJson(strEncoded: String): String {
val decodedBytes: ByteArray = Base64.decode(strEncoded, Base64.URL_SAFE)
return String(decodedBytes, charset("UTF-8"))
}
fun processJWT(acc_token : String) : MutableList<Any>{
Log.i("Access Token Received", acc_token)
val decoded = JWTUtils.decoded(acc_token)
return decoded
}
}JWTHeader data type
data class JWTHeader (
@SerializedName("alg")
val alg : String,
@SerializedName("typ")
val typ : String
)JWTBody ( the payload ) – this could vary
data class JWTBody (
@SerializedName("id")
val id : Int,
@SerializedName("username")
val username : String,
@SerializedName("job")
val job : String,
@SerializedName("iat")
val iat : String
)To use it, do the following
val decoded = JWTUtils.decoded(acc_token)
if (decoded.isNotEmpty()) {
val header: JWTHeader = decoded[0] as JWTHeader
val body: JWTBody = decoded[1] as JWTBody
//process
}
