A data contract is an agreed schema and interpretation for data exchanged between software components or services. It defines how structured data is serialized, deserialized, and evolved without silently breaking consumers. section 12.2
Contract failures can hide behind dropped fields, default values, or delayed deserialization errors. Investigate the producer’s schema, the consumer’s model, field optionality, enum changes, and Java serialization identifiers before blaming the transport. section 12.2
Reliable contract evolution depends on:
- Maintaining forward and backward compatibility so services can evolve independently. section 12.2
- Treating Protobuf schemas and generated classes as shared service boundaries rather than local implementation details. section 12.2
- Checking whether added fields, renamed enums, or changed models are understood consistently by every participant. section 12.2
message Order {
int64 id = 1;
string customer_id = 2;
repeated string items = 3;
optional string notes = 4;
}
Use the schema to inspect field numbers, types, repetition, and optionality before changing a message exchanged between services. section 12.2
