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
> <javascript:>> 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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