io.apptik.comm.jus.converter.ProtoConverterFactory Maven / Gradle / Ivy

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Communication library for Android and Java

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/*
 * Copyright (C) 2015 AppTik Project
 * Copyright (C) 2013 Square, 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 io.apptik.comm.jus.converter;

import com.google.protobuf.MessageLite;
import com.google.protobuf.Parser;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Type;

import io.apptik.comm.jus.Converter;
import io.apptik.comm.jus.NetworkRequest;
import io.apptik.comm.jus.NetworkResponse;

/**
 * A {@linkplain Converter.Factory converter} which uses Protocol Buffers.
 * 
 * This converter only applies for types which extend from {@link MessageLite} (or one of its
 * subclasses).
 */
public final class ProtoConverterFactory extends Converter.Factory {
    public static ProtoConverterFactory create() {
        return new ProtoConverterFactory();
    }

    @Override
    public Converter fromResponse(Type type, Annotation[] annotations) {
        if (!(type instanceof Class)) {
            return null;
        }
        Class c = (Class) type;
        if (!MessageLite.class.isAssignableFrom(c)) {
            return null;
        }

        Parser parser;
        try {
            Field field = c.getDeclaredField("PARSER");
            //noinspection unchecked
            parser = (Parser) field.get(null);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new IllegalArgumentException(
                    "Found a protobuf message but " + c.getName() + " had no PARSER field.");
        }
        return new ProtoResponseConverter<>(parser);
    }

    @Override
    public Converter toRequest(Type type, Annotation[] annotations) {
        if (!(type instanceof Class)) {
            return null;
        }
        if (!MessageLite.class.isAssignableFrom((Class) type)) {
            return null;
        }
        return new ProtoRequestConverter<>();
    }
}