ProtoConverter.java

// Copyright 2013 Square, Inc.
package retrofit.converter;

import com.google.protobuf.AbstractMessageLite;
import retrofit.mime.TypedByteArray;
import retrofit.mime.TypedInput;
import retrofit.mime.TypedOutput;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

/**
 * A {@link Converter} that reads and writes protocol buffers.
 */
public class ProtoConverter implements Converter
{
  private static final String MIME_TYPE = "application/x-protobuf";

  @Override
  public Object fromBody(TypedInput body, Type type) throws ConversionException
  {
    if (!(type instanceof Class<?>))
    {
      throw new IllegalArgumentException("Expected a raw Class<?> but was " + type);
    }
    Class<?> c = (Class<?>) type;
    if (!AbstractMessageLite.class.isAssignableFrom(c))
    {
      throw new IllegalArgumentException("Expected a protobuf message but was " + c.getName());
    }

    String mimeType = body.mimeType();
    if (!MIME_TYPE.equals(mimeType))
    {
      throw new ConversionException("Response content type was not a proto: " + mimeType);
    }

    try
    {
      Method parseFrom = c.getMethod("parseFrom", InputStream.class);
      return parseFrom.invoke(null, body.in());
    }
    catch (InvocationTargetException e)
    {
      throw new ConversionException(c.getName() + ".parseFrom() failed", e.getCause());
    }
    catch (NoSuchMethodException e)
    {
      throw new IllegalArgumentException("Expected a protobuf message but was " + c.getName());
    }
    catch (IllegalAccessException e)
    {
      throw new AssertionError();
    }
    catch (IOException e)
    {
      throw new ConversionException(e);
    }
  }

  @Override
  public TypedOutput toBody(Object object)
  {
    if (!(object instanceof AbstractMessageLite))
    {
      throw new IllegalArgumentException(
          "Expected a protobuf message but was " + (object != null ? object.getClass().getName()
                                                                   : "null"));
    }
    byte[] bytes = ((AbstractMessageLite) object).toByteArray();
    return new TypedByteArray(MIME_TYPE, bytes);
  }
}