Gson type adapter to serialize and deserialize byte arrays in base64

GsonHelper.java

import java.lang.reflect.Type;

import android.util.Base64;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class GsonHelper {
    public static final Gson customGson = new GsonBuilder().registerTypeHierarchyAdapter(byte[].class,
            new ByteArrayToBase64TypeAdapter()).create();

    // Using Android's base64 libraries. This can be replaced with any base64 library.
    private static class ByteArrayToBase64TypeAdapter implements JsonSerializer<byte[]>, JsonDeserializer<byte[]> {
        public byte[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            return Base64.decode(json.getAsString(), Base64.NO_WRAP);
        }

        public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
            return new JsonPrimitive(Base64.encodeToString(src, Base64.NO_WRAP));
        }
    }
}

very useful. thanks.

Thanks great help

how do I serialize and deserialize?
I use:
customGson.toJson(jsonObject, osw);
and:
result = customGson.fromJson(reader, type);
however, the serialize and deserialize functions are not called and I am still getting the serialized output in pretty json string format

👍

thanks very much

@JiboStore

You can register typeAdapters like so:

GsonBuilder builder = new GsonBuilder();

// Adapter to convert a Unix Long Time in Json to a java.util.Date object
builder.registerTypeAdapter(Date.class, new JsonDeserializer<Date>() {
    public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        return new Date(json.getAsJsonPrimitive().getAsLong());
    }
});

// Adapter to convert byte[] in a Java Object to a String in Json for UI to display image properly
builder.registerTypeAdapter(byte[].class, new JsonSerializer<byte[]>() {
    public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(Base64.getEncoder().encodeToString(src));
    }
});

Gson gson = builder.create();

And then to use:

// Deserialize | You have a Json string with a Unix Long Time and you want to convert to a Date object inside YourJavaObject
YourJavaObject obj = gson.fromJson(jsonStringHere, YourJavaObject.class);

// Serialize | YourJavaObject has a byte[] and you want to convert it to a String in your Json
String json = gson.toJson(yourJavaObjectHere);

Thank you. Using org.apache.commons.codec.binary.Base64 this methods seems to be working:

@Override
public byte[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
	return Base64.decodeBase64(json.getAsString());
}

@Override
public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
	return new JsonPrimitive(Base64.encodeBase64String(src));
}

Using Java 1.8, with Lambdas, I have serialization a deserialization of byte arrays to Base64 with this code:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(byte[].class, (JsonSerializer<byte[]>) (src, typeOfSrc, context) -> new JsonPrimitive(Base64.getEncoder().encodeToString(src)));
builder.registerTypeAdapter(byte[].class, (JsonDeserializer<byte[]>) (json, typeOfT, context) -> Base64.getDecoder().decode(json.getAsString()));
Gson gson = builder.create();

thank you so much.

thank you!!!

Thanks!!!

Using Java 1.8, with Lambdas, I have serialization a deserialization of byte arrays to Base64 with this code:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(byte[].class, (JsonSerializer<byte[]>) (src, typeOfSrc, context) -> new JsonPrimitive(Base64.getEncoder().encodeToString(src)));
builder.registerTypeAdapter(byte[].class, (JsonDeserializer<byte[]>) (json, typeOfT, context) -> Base64.getDecoder().decode(json.getAsString()));
Gson gson = builder.create();

Thanks!