Serve idempotent unary RPCs over HTTP GET.
Idempotent unary RPCs — those annotated with option idempotency_level = NO_SIDE_EFFECTS; — may be issued as HTTP GET.
There is no request body to negotiate, so Connect GET does not go through ContentNegotiation.
With stock connectJson() and no custom TypeRegistry, nothing extra is required.
The GET codec stack resolves through defaults that match the POST JSON path.
If POST uses a custom registry, GET must see the same one or Any fields fail at runtime:
val typeRegistry = TypeRegistry.newBuilder()
.add(SayRequest.getDescriptor())
.build()
embeddedServer(CIO, port = 8080) {
install(Resources)
installConnectGetCodecs(
ConnectGetStrategies(
proto = GoogleJavaProtobufStrategy(),
// Covers request deserialisation (and response serialisation when
// jsonSerializer is unset). See below if responses embed Any.
json = GoogleJavaJSONStrategy(typeRegistry),
),
)
routing {
install(ContentNegotiation) {
connectJson(typeRegistry)
}
elizaService(ElizaServiceHandler)
}
}.start(wait = true)GoogleJavaJSONStrategy(typeRegistry) forwards the registry to the parser, not the printer.
When responses also embed Any, pass a jsonSerializer backed by
JsonFormat.printer().usingTypeRegistry(typeRegistry):
installConnectGetCodecs(
ConnectGetStrategies(
proto = GoogleJavaProtobufStrategy(),
json = GoogleJavaJSONStrategy(typeRegistry),
jsonSerializer = object : ConnectGetJsonSerializer {
private val printer = JsonFormat.printer().usingTypeRegistry(typeRegistry)
override fun <T : Any> serialize(value: T, clazz: KClass<T>): ByteArray =
printer.print(value as Message).toByteArray(Charsets.UTF_8)
},
),
)Netty covers the Connect GET conformance cases fully.
CIO passes except cases that rely on duplicate request headers, which CIO collapses upstream.
Those pins live in conformance/known-failing-cio.txt.