JsonObjectDeserializationVisitor.java

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.smartandroid.sa.json;

import java.lang.reflect.Type;

/**
 * A visitor that populates fields of an object with data from its equivalent
 * JSON representation
 * 
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
final class JsonObjectDeserializationVisitor<T> extends
		JsonDeserializationVisitor<T> {

	JsonObjectDeserializationVisitor(JsonElement json, Type type,
			ObjectNavigator objectNavigator,
			FieldNamingStrategy2 fieldNamingPolicy,
			ObjectConstructor objectConstructor,
			ParameterizedTypeHandlerMap<JsonDeserializer<?>> deserializers,
			JsonDeserializationContext context) {
		super(json, type, objectNavigator, fieldNamingPolicy,
				objectConstructor, deserializers, context);
	}

	@Override
	@SuppressWarnings("unchecked")
	protected T constructTarget() {
		return (T) objectConstructor.construct(targetType);
	}

	public void startVisitingObject(Object node) {
		// do nothing
	}

	public void visitArray(Object array, Type componentType) {
		// should not be called since this case should invoke
		// JsonArrayDeserializationVisitor
		throw new JsonParseException("Expecting object but found array: "
				+ array);
	}

	public void visitObjectField(FieldAttributes f, Type typeOfF, Object obj) {
		try {
			if (!json.isJsonObject()) {
				throw new JsonParseException("Expecting object found: " + json);
			}
			JsonObject jsonObject = json.getAsJsonObject();
			String fName = getFieldName(f);
			JsonElement jsonChild = jsonObject.get(fName);
			if (jsonChild != null) {
				Object child = visitChildAsObject(typeOfF, jsonChild);
				f.set(obj, child);
			} else {
				f.set(obj, null);
			}
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	public void visitArrayField(FieldAttributes f, Type typeOfF, Object obj) {
		try {
			if (!json.isJsonObject()) {
				throw new JsonParseException("Expecting object found: " + json);
			}
			JsonObject jsonObject = json.getAsJsonObject();
			String fName = getFieldName(f);
			JsonArray jsonChild = (JsonArray) jsonObject.get(fName);
			if (jsonChild != null) {
				Object array = visitChildAsArray(typeOfF, jsonChild);
				f.set(obj, array);
			} else {
				f.set(obj, null);
			}
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	private String getFieldName(FieldAttributes f) {
		return fieldNamingPolicy.translateName(f);
	}

	public boolean visitFieldUsingCustomHandler(FieldAttributes f,
			Type declaredTypeOfField, Object parent) {
		try {
			String fName = getFieldName(f);
			if (!json.isJsonObject()) {
				throw new JsonParseException("Expecting object found: " + json);
			}
			JsonElement child = json.getAsJsonObject().get(fName);
			boolean isPrimitive = Primitives.isPrimitive(declaredTypeOfField);
			if (child == null) { // Child will be null if the field wasn't
									// present in Json
				return true;
			} else if (child.isJsonNull()) {
				if (!isPrimitive) {
					f.set(parent, null);
				}
				return true;
			}
			ObjectTypePair objTypePair = new ObjectTypePair(null,
					declaredTypeOfField, false, false);
			Pair<JsonDeserializer<?>, ObjectTypePair> pair = objTypePair
					.getMatchingHandler(deserializers);
			if (pair == null) {
				return false;
			}
			Object value = invokeCustomDeserializer(child, pair);
			if (value != null || !isPrimitive) {
				f.set(parent, value);
			}
			return true;
		} catch (IllegalAccessException e) {
			throw new RuntimeException();
		}
	}

	@SuppressWarnings("unchecked")
	public void visitPrimitive(Object primitive) {
		if (!json.isJsonPrimitive()) {
			throw new JsonParseException(
					"Type information is unavailable, and the target object is not a primitive: "
							+ json);
		}
		JsonPrimitive prim = json.getAsJsonPrimitive();
		target = (T) prim.getAsObject();
	}
}