Converting JSON between string and byte[] with GSON

Question

I am using hibernate to map objects to the database. A client (an iOS app) sends me particular objects in JSON format which I convert to their true representation using the

Answer 1

From some blog for future reference, incase the link is not available, atleast users can refer here.

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;

import java.lang.reflect.Type;
import java.util.Date;

public class GsonHelper {
    public static final Gson customGson = new GsonBuilder()
            .registerTypeAdapter(Date.class, new JsonDeserializer<Date>() {
                @Override
                public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
                return new Date(json.getAsLong());
                }
            })
            .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));
        }
    }
}

Answer 2

You can simply take the photo as String in POJO , and in Setter method convert String to byte[] and return byte[] in Getter method

@Entity
@Table(name = "PersonalCard")
public class PersonalCard implements Card
{

    @Id @GeneratedValue
    @Column(name = "id")
    private int id;

    @OneToOne
    @JoinColumn(name="userid")
    private int userid;

    @Column(name = "homephonenumber")
    protected String homeContactNumber;

    @Column(name = "mobilephonenumber")
    protected String mobileContactNumber;

    @Column(name = "photo")
    private byte[] optionalImage;

    @Column(name = "address")
    private String address;

    @Column
    byte[] optionalImage;

    public byte[] getOptionalImage()
    {
        return optionalImage;
    }

    public void setOptionalImage(String s)
    {
        this.optionalImage= s.getBytes();
    }
}

Answer 3

You can use this adapter to serialize and deserialize byte arrays in base64. Here's the content.

   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));
        }
    }

Credit to the author Ori Peleg.