"Unparseable date: 1302828677828" trying to deserialize with Gson a millisecond-format date received from server

Alfonso's comment:

Finally I got the solution:

// Creates the json object which will manage the information received GsonBuilder builder = new GsonBuilder(); // Register an adapter to manage the date types as long values builder.registerTypeAdapter(Date.class, new JsonDeserializer<Date>() {    public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {      return new Date(json.getAsJsonPrimitive().getAsLong());    } });Gson gson = builder.create();

I wrote an ImprovedDateTypeAdapter based on GSON default DateTypeAdapter that supports default dates format and the timestamp (long) format.

import com.google.gson.Gson;import com.google.gson.JsonSyntaxException;import com.google.gson.TypeAdapter;import com.google.gson.TypeAdapterFactory;import com.google.gson.reflect.TypeToken;import com.google.gson.stream.JsonReader;import com.google.gson.stream.JsonToken;import com.google.gson.stream.JsonWriter;import java.io.IOException;import java.text.DateFormat;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Locale;import java.util.TimeZone;public final class ImprovedDateTypeAdapter extends TypeAdapter<Date> {    public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {            @SuppressWarnings("unchecked")            TypeAdapter<T> typeAdapter = (TypeAdapter<T>) ((typeToken.getRawType() == Date.class) ? new ImprovedDateTypeAdapter()                    : null);            return typeAdapter;        }    };    private final DateFormat enUsFormat;    private final DateFormat localFormat;    private final DateFormat iso8601Format;    public ImprovedDateTypeAdapter() {        this.enUsFormat = DateFormat.getDateTimeInstance(2, 2, Locale.US);        this.localFormat = DateFormat.getDateTimeInstance(2, 2);        this.iso8601Format = buildIso8601Format();    }    private static DateFormat buildIso8601Format() {        DateFormat iso8601Format = new SimpleDateFormat(                "yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);        iso8601Format.setTimeZone(TimeZone.getTimeZone("UTC"));        return iso8601Format;    }    public Date read(JsonReader in) throws IOException {        if (in.peek() == JsonToken.NULL) {            in.nextNull();            return null;        }        return deserializeToDate(in.nextString());    }    private synchronized Date deserializeToDate(String json) {        try {            return new Date(Long.parseLong(json));        } catch (Exception e) {            try {                return this.localFormat.parse(json);            } catch (ParseException e1) {                try {                    return this.enUsFormat.parse(json);                } catch (ParseException e2) {                    try {                        return this.iso8601Format.parse(json);                    } catch (ParseException e3) {                        throw new JsonSyntaxException(json, e3);                    }                }            }        }    }    public synchronized void write(JsonWriter out, Date value)            throws IOException {        if (value == null) {            out.nullValue();            return;        }        String dateFormatAsString = this.enUsFormat.format(value);        out.value(dateFormatAsString);    }}

To use it:

// Creates the json object which will manage the information received GsonBuilder builder = new GsonBuilder(); // Register an adapter to manage the date types as long values builder.registerTypeAdapter(Date.class, new ImprovedDateTypeAdapter());Gson gson = builder.create();

JsonSerializer<Date> serializer= new JsonSerializer<Date>() {  @Override  public JsonElement serialize(Date src, Type typeOfSrc, JsonSerializationContext              context) {    return src == null ? null : new JsonPrimitive(src.getTime());  }};JsonDeserializer<Date> deserializer= new JsonDeserializer<Date>() {  @Override  public Date deserialize(JsonElement json, Type typeOfT,       JsonDeserializationContext context) throws JsonParseException {    return json == null ? null : new Date(json.getAsLong());  }};Gson gson = new GsonBuilder()   .registerTypeAdapter(Date.class, serializer)   .registerTypeAdapter(Date.class, deserializer).create();