ContextInjectorTypeAdapaterFactory.java

/**
 * 
 * Funf: Open Sensing Framework
 * Copyright (C) 2010-2011 Nadav Aharony, Wei Pan, Alex Pentland.
 * Acknowledgments: Alan Gardner
 * Contact: nadav@media.mit.edu
 * 
 * This file is part of Funf.
 * 
 * Funf is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 * 
 * Funf is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with Funf. If not, see <http://www.gnu.org/licenses/>.
 * 
 */
package edu.mit.media.funf.config;

import java.io.IOException;
import java.lang.reflect.Field;

import android.content.Context;
import android.util.Log;

import com.google.gson.Gson;
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.JsonWriter;

import edu.mit.media.funf.util.AnnotationUtil;

import static edu.mit.media.funf.util.LogUtil.TAG;

public class ContextInjectorTypeAdapaterFactory implements TypeAdapterFactory {

	public static final String CONTEXT_FIELD = "context";
	
	private Context context;
	private TypeAdapterFactory delegate;
	
	public ContextInjectorTypeAdapaterFactory(Context context, TypeAdapterFactory delegate) {
		if (context == null) {
			throw new RuntimeException("Context cannot be null.");
		}
		this.context = context;
		this.delegate = delegate;
	}
	
	@Override
	public <T> TypeAdapter<T> create(final Gson gson, final TypeToken<T> type) {
		final TypeAdapter<T> delegateAdapter = delegate.create(gson, type);
		if (delegateAdapter == null) {
			return null;
		} else {
			return new TypeAdapter<T>() {
				
				@Override
				public void write(JsonWriter out, T value) throws IOException {
					delegateAdapter.write(out, value);
				}
	
				@Override
				public T read(JsonReader in) throws IOException {
					T value = delegateAdapter.read(in);
					if (value != null) {
						try {
							Field contextField = AnnotationUtil.getField(CONTEXT_FIELD, value.getClass());
							if (contextField != null && Context.class.isAssignableFrom(contextField.getType())) {
								boolean isAccessible = contextField.isAccessible();
								contextField.setAccessible(true);
								contextField.set(value, context);
								contextField.setAccessible(isAccessible);
							}
						} catch (SecurityException e) {
							// Swallow
							Log.v(TAG, e.getMessage());
						} catch (IllegalArgumentException e) {
							// Swallow
							Log.v(TAG, e.getMessage());
						} catch (IllegalAccessException e) {
							// Swallow
							Log.v(TAG, e.getMessage());
						}
					}
					return value;
				}
			};
		}
	}

}