At no point are you specifying that you want to use the
"MessagePublish" descriptor, so you must still be using the API
incorrectly...

On Fri, Oct 31, 2014 at 5:10 PM, Pradeep Gollakota <pradeep...@gmail.com> wrote:
> Ok… awesome… I do have the .proto’s ahead of time, so I can have them
> compiled to the .desc files and store those.
>
> Here’s my .proto file:
>
> package com.lithum.pbnj;
>
> import "google/protobuf/descriptor.proto";
>
> option java_package = "com.lithium.pbnj";
>
> extend google.protobuf.FieldOptions {
>     optional bool isPii = 50101;
> }
>
> message MessagePublish {
>     required string uuid = 1;
>     required int64 timestamp = 2;
>     required int64 message_uid = 3;
>     required string message_content = 4;
>     required int64 message_author_uid = 5;
>     optional string email = 6 [(isPii) = true];
> }
>
> I compiled this .proto file into a .desc file using the command you gave me.
> I’m now trying to parse a DynamicMessage from the .desc file. Here’s the
> code I have so far.
>
>         DescriptorProtos.FileDescriptorSet descriptorSet =
> DescriptorProtos.FileDescriptorSet.parseFrom(PBnJ.class.getResourceAsStream("/messages.desc"));
>         Descriptors.Descriptor desc =
> descriptorSet.getFile(0).getDescriptorForType();
>
>         Messages.MessagePublish event = Messages.MessagePublish.newBuilder()
>                 .setUuid(UUID.randomUUID().toString())
>                 .setTimestamp(System.currentTimeMillis())
>                 .setEmail("he...@example.com")
>                 .setMessageAuthorUid(1)
>                 .setMessageContent("hello world!")
>                 .setMessageUid(1)
>                 .build();
>
>         DynamicMessage dynamicMessage = DynamicMessage.parseFrom(desc,
> event.toByteArray());
>
> The final line in the above code is throwing the following exception:
>
> Exception in thread "main"
> com.google.protobuf.InvalidProtocolBufferException: Protocol message
> end-group tag did not match expected tag.
>     at
> com.google.protobuf.InvalidProtocolBufferException.invalidEndTag(InvalidProtocolBufferException.java:94)
>     at
> com.google.protobuf.CodedInputStream.checkLastTagWas(CodedInputStream.java:174)
>     at
> com.google.protobuf.CodedInputStream.readMessage(CodedInputStream.java:478)
>     at
> com.google.protobuf.MessageReflection$BuilderAdapter.parseMessage(MessageReflection.java:482)
>     at
> com.google.protobuf.MessageReflection.mergeFieldFrom(MessageReflection.java:780)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:336)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:318)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:229)
>     at
> com.google.protobuf.AbstractMessageLite$Builder.mergeFrom(AbstractMessageLite.java:180)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:419)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:229)
>     at
> com.google.protobuf.AbstractMessageLite$Builder.mergeFrom(AbstractMessageLite.java:171)
>     at
> com.google.protobuf.AbstractMessage$Builder.mergeFrom(AbstractMessage.java:412)
>     at com.google.protobuf.DynamicMessage.parseFrom(DynamicMessage.java:119)
>     at com.lithium.pbnj.PBnJ.main(PBnJ.java:36)
>     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>     at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
>     at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>     at java.lang.reflect.Method.invoke(Method.java:483)
>     at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
>
> On Friday, October 31, 2014 11:39:27 AM UTC-7, Oliver wrote:
>>
>> Basically, you can't do that in pure Java - the compiler is a C++
>> binary, there is no Java version.
>>
>> Still, working with the output of --descriptor_set_out is probably the
>> way to go here. If you have the .proto file ahead of time, you can
>> pregenerate the descriptor output at build time and store it instead
>> of the .proto file. If you don't have the .proto file ahead of time
>> (and you can't redesign - this is not a good design) then you could
>> run the compiler at runtime and read the output. Either way, now you
>> have a parsed version of the message format as a protobuf-encoded
>> message that you can read into your Java program and extract the
>> Descriptors you need.
>>
>> If you're looking at a selfdescribing message format, then I'd go with
>> using the parsed descriptors as your format description, not the text
>> .proto file.
>>
>> Oliver
>>
>>
>> On 31 October 2014 17:56, Pradeep Gollakota <prade...@gmail.com> wrote:
>> > Hi Oliver,
>> >
>> > Thanks for the response! I guess my question wasn't quite clear. In my
>> > java
>> > code I have a string which contains the content of a .proto file. Given
>> > this
>> > string, how can I create an instance of a Descriptor class so I can do
>> > DynamicMessage parsing.
>> >
>> > Thanks!
>> > - Pradeep
>> >
>> > On Thursday, October 30, 2014 2:41:19 PM UTC-7, Oliver wrote:
>> >>
>> >> On 30 October 2014 02:53, Pradeep Gollakota <prade...@gmail.com> wrote:
>> >>
>> >> > I have a use case where I need to parse messages without having the
>> >> > corresponding precompiled classes in Java. So the DynamicMessage
>> >> > seems
>> >> > to be
>> >> > the correct fit, but I'm not sure how I can generate the
>> >> > DescriptorSet
>> >> > from
>> >> > the ".proto" definition.
>> >>
>> >> protoc --descriptor_set_out=FILE ?
>> >>
>> >> Oliver
>> >
>> > --
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>
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