On Tue, Jun 2, 2015 at 5:41 AM, Mikhail Melnik <[email protected]>
wrote:
> Hi, everyone.
>
> I have a vague idea of the purpose and common usage of the protobuf Any
> type.
>
> Our team use java protobuf library.
> We try to describe domain we're working on in protobuf terms and use Any
> as wrapper for unknown messages on compile time.
>
> In some fields we keep Any as general type for any message so we do
> wrapping like this:
>
> Any result = Any.newBuilder()
> .setTypeUrl(message.getClass().getClassName())
> .setValue(message.toByteString())
> .build();
>
>
> to wrap our messages and later unwrap them and cast to certain message
> type.
> We don't like fact that we use Java className as the type url, but didn't
> find better way yet.
>
> We would like to put there protobuf message name:
>
> message.getDescriptorForType().getFullName()
>
>
> but we didn't find nice way to parse such Any object back to certain
> Message.
>
> We also tried to find more documentation on Any type and understand what
> is the common usage of it.
> Looks like there should be some utility methods to work with Any but they
> are not implemented yet.
>
> Can anyone from google share their vision about usage of Any or point to
> documentation if we missed something there?
> If anyone did use protobuf Any type and can make examples from own
> experience it would be also very useful.
>
In Java, the Any message will have several additional methods to do
packing/unpacking. The method signature proposed looks like this:
class Any extends GeneratedMessage {
static <T extends Message> Any pack(T value);
// Throws exceptions if parsing fails or the type url doesn't match.
<T extends Message> T unpack(Class<T> clazz);
<T extends Message> boolean is(Class<T> clazz);
}
With these, your code could be simplified to:
Any result = Any.pack(message);
The default type url will be used (i.e.,
type.googleapis.com/full.message.name) in these methods.
>
> Thanks in advance!
>
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