Example usage for com.google.gson TypeAdapter toJsonTree

List of usage examples for com.google.gson TypeAdapter toJsonTree

  1. HOME
  2. Java
  3. com.google.gson
  4. com.google.gson.*
  5. TypeAdapter
  6. toJsonTree

Introduction

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

Prototype

public final JsonElement toJsonTree(T value)

Source Link

Document

Converts value to a JSON tree.

Usage

From source file:com.metinkale.prayerapp.vakit.times.gson.RuntimeTypeAdapterFactory.java

License:Apache License

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

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
    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, @NonNull 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();
}

From source file:com.michaelfotiadis.crossyscore.core.data.parsers.gson.RuntimeTypeAdapterFactory.java

License:Apache License

public <R> TypeAdapter<R> create(final Gson gson, final TypeToken<R> type) {
    if (!type.getRawType().equals(baseType)) {
        return null;
    }//from   ww w  . ja v  a2 s .  c o  m

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();

    for (final Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
        final 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 void write(final JsonWriter out, final R value) throws IOException {
            if (value != null) {
                final Class<?> srcType = value.getClass();
                final String label = subtypeToLabel.get(srcType);
                @SuppressWarnings("unchecked")
                final // 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?");
                }
                final 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);
                }
                final JsonObject clone = new JsonObject();
                clone.add(typeFieldName, new JsonPrimitive(label));
                for (final Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
                    clone.add(e.getKey(), e.getValue());
                }
                Streams.write(clone, out);
            } else {
                out.nullValue();
            }
        }

        @Override
        public R read(final JsonReader in) throws IOException {
            final JsonElement jsonElement = Streams.parse(in);
            // fix for null Json Elements
            if (jsonElement.isJsonNull()) {
                return null;
            }

            final JsonElement labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
            final String label = getBaseTypeLabel(labelJsonElement);
            @SuppressWarnings("unchecked") // registration requires that subtype extends T
            final 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);
        }

        private String getBaseTypeLabel(final JsonElement labelJsonElement) {
            final String label;

            if (labelJsonElement == null) {
                if (defaultSubTypeLabel == null) {
                    throw new JsonParseException("cannot deserialize " + baseType
                            + " because it does not define a field named " + typeFieldName);
                } else {
                    label = defaultSubTypeLabel;

                    if (!labelToDelegate.containsKey(label)) {
                        throw new IllegalStateException(
                                "WTF: Was looking for " + label + " in " + labelToDelegate.keySet());
                    }

                }
            } else {
                label = labelJsonElement.getAsString();
            }

            return label;
        }
    };
}

From source file:com.michaelfotiadis.steam.net.gson.RuntimeTypeAdapterFactory.java

License:Apache License

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

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();

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

    return new TypeAdapter<R>() {
        private String getBaseTypeLabel(final JsonElement labelJsonElement) {
            final String label;

            if (labelJsonElement == null) {
                if (defaultSubTypeLabel == null) {
                    throw new JsonParseException("cannot deserialize " + baseType
                            + " because it does not define a field named " + typeFieldName);
                } else {
                    label = defaultSubTypeLabel;

                    if (!labelToDelegate.containsKey(label)) {
                        throw new IllegalStateException(
                                "WTF: Was looking for " + label + " in " + labelToDelegate.keySet());
                    }

                }
            } else {
                label = labelJsonElement.getAsString();
            }

            return label;
        }

        @Override
        public R read(final JsonReader in) throws IOException {
            final JsonElement jsonElement = Streams.parse(in);
            // fix for null Json Elements
            if (jsonElement.isJsonNull()) {
                return null;
            }

            final JsonElement labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
            final String label = getBaseTypeLabel(labelJsonElement);
            @SuppressWarnings("unchecked") // registration requires that subtype extends T
            final 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(final JsonWriter out, final R value) throws IOException {
            if (value != null) {
                final Class<?> srcType = value.getClass();
                final String label = subtypeToLabel.get(srcType);
                @SuppressWarnings("unchecked")
                final // 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?");
                }
                final 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);
                }
                final JsonObject clone = new JsonObject();
                clone.add(typeFieldName, new JsonPrimitive(label));
                for (final Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
                    clone.add(e.getKey(), e.getValue());
                }
                Streams.write(clone, out);
            } else {
                out.nullValue();
            }
        }
    };
}

From source file:com.prayer.vakit.times.gson.RuntimeTypeAdapterFactory.java

License:Apache License

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

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
    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();
}

From source file:com.truethat.android.external.gson.RuntimeTypeAdapterFactory.java

License:Apache License

/**
 * This method was modified, to include {@link #typeFieldName} in serialized registered sub types.
 *//*w  w w .  j  a v a  2s  . com*/
@Nullable
public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
    if (type.getRawType() != baseType && !labelToSubtype.containsKey(type.getRawType().getSimpleName())) {
        return null;
    }

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
    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 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);
        }

        @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);
        }
    }.nullSafe();
}

From source file:com.vaadin.addon.charts.model.gsonhelpers.AbstractSeriesTypeAdapterFactory.java

private TypeAdapter<AbstractSeries> customizeMyClassAdapter(Gson gson, TypeToken<AbstractSeries> type) {
    final TypeAdapter<AbstractSeries> delegate = gson.getDelegateAdapter(this, type);
    final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
    return new TypeAdapter<AbstractSeries>() {
        @Override//from w ww. j  ava  2s . co m
        public void write(JsonWriter out, AbstractSeries value) throws IOException {
            JsonObject tree = (JsonObject) delegate.toJsonTree(value);

            // "flatten" series specific plot options at series level. see
            // Higchart API for details
            if (value.getPlotOptions() != null) {
                JsonObject plotOptionsJson = (JsonObject) tree.remove("plotOptions");
                if (plotOptionsJson != null) {
                    Set<Entry<String, JsonElement>> entrySet = plotOptionsJson.entrySet();
                    for (Entry<String, JsonElement> entry : entrySet) {
                        tree.add(entry.getKey(), entry.getValue());
                    }
                    tree.addProperty("type", value.getPlotOptions().getChartType().toString());
                }
            }
            elementAdapter.write(out, tree);
        }

        // This is never used
        @Override
        public AbstractSeries read(JsonReader in) throws IOException {
            JsonElement tree = elementAdapter.read(in);
            return delegate.fromJsonTree(tree);
        }
    };
}

From source file:com.vaadin.addon.charts.model.gsonhelpers.DataSeriesItemTypeAdapterFactory.java

private TypeAdapter<DataSeriesItem> customizeMyClassAdapter(Gson gson, TypeToken<DataSeriesItem> type) {
    final TypeAdapter<DataSeriesItem> delegate = gson.getDelegateAdapter(this, type);
    final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
    return new TypeAdapter<DataSeriesItem>() {
        @Override/*from w ww .  j  av a 2 s . c  om*/
        public void write(JsonWriter out, DataSeriesItem value) throws IOException {
            if (value.isCustomized()) {
                elementAdapter.write(out, delegate.toJsonTree(value));
            } else {
                Number x = value.getX();
                Number y = value.getY();
                if (x != null) {
                    JsonArray jsonArray = new JsonArray();
                    jsonArray.add(new JsonPrimitive(x));
                    if (y != null) {
                        jsonArray.add(new JsonPrimitive(y));
                    } else if (value.getLow() != null) {
                        jsonArray.add(new JsonPrimitive(value.getLow()));
                        jsonArray.add(new JsonPrimitive(value.getHigh()));
                    } else {
                        jsonArray.add(JsonNull.INSTANCE);
                        jsonArray.add(JsonNull.INSTANCE);
                    }
                    elementAdapter.write(out, jsonArray);
                } else {
                    // If no x set, make it like list series, just number or
                    // min-max pairs
                    if (y != null) {
                        elementAdapter.write(out, new JsonPrimitive(y));
                    } else {
                        JsonArray jsonArray = new JsonArray();
                        jsonArray.add(new JsonPrimitive(value.getLow()));
                        jsonArray.add(new JsonPrimitive(value.getHigh()));
                        elementAdapter.write(out, jsonArray);
                    }
                }
            }
        }

        // This is never used
        @Override
        public DataSeriesItem read(JsonReader in) throws IOException {
            JsonElement tree = elementAdapter.read(in);
            return delegate.fromJsonTree(tree);
        }
    };
}

From source file:com.vaadin.addon.charts.model.gsonhelpers.TitleTypeAdapterFactory.java

private TypeAdapter<Title> customizeMyClassAdapter(Gson gson, TypeToken<Title> type) {
    final TypeAdapter<Title> delegate = gson.getDelegateAdapter(this, type);
    final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
    return new TypeAdapter<Title>() {
        @Override// w w  w  .  j a  va2  s .c om
        public void write(JsonWriter out, Title value) throws IOException {
            // null for text is significant, else there will be
            // "Chart Title" as default
            if (value != null && value.getText() == null) {
                boolean serializeNulls = out.getSerializeNulls();
                out.setSerializeNulls(true);
                out.beginObject();
                out.name("text");
                out.nullValue();
                out.endObject();
                out.setSerializeNulls(serializeNulls);
            } else {
                elementAdapter.write(out, delegate.toJsonTree(value));
            }
        }

        // This is never used
        @Override
        public Title read(JsonReader in) throws IOException {
            JsonElement tree = elementAdapter.read(in);
            return delegate.fromJsonTree(tree);
        }
    };
}

From source file:com.wix.mediaplatform.gson.RuntimeTypeAdapterFactory.java

License:Apache License

public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
    if (null == type || !baseType.isAssignableFrom(type.getRawType())) {
        return null;
    }// ww  w.ja v  a  2 s . c om

    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
    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().get(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();
}

From source file:cz.boris.gson.typeadapter.RuntimeTypeAdapterFactory.java

License:Apache License

public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
    if (type.getRawType() != baseType) {
        return null;
    }//  w  ww. ja  v  a  2s . 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);
        }
    };
}