Java Protobuf Selector and Mapper?
Kristian Rickert
Hi everyone,
I've created a Java utility for mapping between Protobuf messages using simple rules and selecting nested data using string paths (like "a.b.c", map["key"], struct.key).
What it does:
- Selector: Retrieve data using a path string (e.g., valueHandler.getValue(msg, "profile.address[\"home\"].zip_code")). Handles nested fields, maps, structs, and unwraps google.protobuf.Value.
- Mapper: Map between different proto messages using rules like:
Java
List<String> rules = Arrays.asList(
"target_field = source.field",
"target_list += source_item", // Append
"target_map[\"key\"] = source_value", // Map put
"-field_to_delete" // Delete
);
Message target = protoMapper.map(sourceMsg, Target.getDescriptor(), rules);
Why? I initially built this for a pipeline mapping step to reduce boilerplate code. It ended up handling quite a few edge cases around type conversion, path resolution, literals, and dynamic message handling.
Question: Would a utility like this be useful to others? Are there established Java libraries that provide this specific rule-based mapping and deep path selection beyond standard reflection or FieldMask projections?
It started as a quick selector but grew more complex. I'm considering making it a standalone library if there's interest.
The current code (WIP) is here: https://github.com/krickert/micronaut-multiproject-example/tree/main/protobuf-models/src/main/java/com/krickert/search/model/mapper
Thanks for any feedback!
