Example usage for com.google.gson TypeAdapter TypeAdapter

Introduction

In this page you can find the example usage for com.google.gson TypeAdapter TypeAdapter.

Prototype

TypeAdapter

Source Link

Usage

From source file:zardoni.matteo.SerializzazioneTimeline.test.RuntimeTypeAdapterFactory.java

License:Apache License

public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
    if (type.getRawType() != baseType) {
        return null;
    }/*from  w ww.j a  va 2 s.c o  m*/

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<String, TypeAdapter<?>>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<Class<?>, TypeAdapter<?>>();
    for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
        TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
        labelToDelegate.put(entry.getKey(), delegate);
        subtypeToDelegate.put(entry.getValue(), delegate);
    }

    return (new TypeAdapter<R>() {
        @Override
        public R read(JsonReader in) throws IOException {
            JsonElement jsonElement = Streams.parse(in);
            JsonElement labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
            if (labelJsonElement == null) {
                throw new JsonParseException("cannot deserialize " + baseType
                        + " because it does not define a field named " + typeFieldName);
            }
            String label = labelJsonElement.getAsString();
            @SuppressWarnings("unchecked") // registration requires that subtype extends T
            TypeAdapter<R> delegate = (TypeAdapter<R>) labelToDelegate.get(label);
            if (delegate == null) {
                throw new JsonParseException("cannot deserialize " + baseType + " subtype named " + label
                        + "; did you forget to register a subtype?");
            }
            return delegate.fromJsonTree(jsonElement);
        }

        @Override
        public void write(JsonWriter out, R value) throws IOException {
            Class<?> srcType = value.getClass();
            String label = subtypeToLabel.get(srcType);
            @SuppressWarnings("unchecked") // registration requires that subtype extends T
            TypeAdapter<R> delegate = (TypeAdapter<R>) subtypeToDelegate.get(srcType);
            if (delegate == null) {
                throw new JsonParseException(
                        "cannot serialize " + srcType.getName() + "; did you forget to register a subtype?");
            }
            JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject();
            if (jsonObject.has(typeFieldName)) {
                throw new JsonParseException("cannot serialize " + srcType.getName()
                        + " because it already defines a field named " + typeFieldName);
            }
            JsonObject clone = new JsonObject();
            clone.add(typeFieldName, new JsonPrimitive(label));
            for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
                clone.add(e.getKey(), e.getValue());
            }
            Streams.write(clone, out);
        }
    }).nullSafe();
}