Protocol buffer objects generated at runtime

Question

a colleague of mine came with an idea of generating protocol buffers classes at runtime. Meaning:

• There is C++ server application and Java client application c

Answer 1

For Java you may find following wrapper API ("protobuf-dynamic") easier to use than the original protobuf API:

https://github.com/os72/protobuf-dynamic

For example:

// Create dynamic schema
DynamicSchema.Builder schemaBuilder = DynamicSchema.newBuilder();
schemaBuilder.setName("PersonSchemaDynamic.proto");

MessageDefinition msgDef = MessageDefinition.newBuilder("Person") // message Person
    .addField("required", "int32", "id", 1)     // required int32 id = 1
    .addField("required", "string", "name", 2)  // required string name = 2
    .addField("optional", "string", "email", 3) // optional string email = 3
    .build();

schemaBuilder.addMessageDefinition(msgDef);
DynamicSchema schema = schemaBuilder.build();

// Create dynamic message from schema
DynamicMessage.Builder msgBuilder = schema.newMessageBuilder("Person");
Descriptor msgDesc = msgBuilder.getDescriptorForType();
DynamicMessage msg = msgBuilder
    .setField(msgDesc.findFieldByName("id"), 1)
    .setField(msgDesc.findFieldByName("name"), "Alan Turing")
    .setField(msgDesc.findFieldByName("email"), "at@sis.gov.uk")
    .build();

Dynamic schemas can be useful in some applications to distribute changes without recompiling code (say in a more dynamically typed system). They can also be very useful for "dumb" applications that require no semantic understanding (say a data browser tool)