JSON

JsonCodec reads and writes JSON through serde_json; it is the default codec, on with the json feature.

The json feature is a default feature of the crate. While it is on, DefaultCodec is JsonCodec, so a handler mounted with no codec named decodes JSON, and a reply is encoded in JSON. A message type derives serde::Deserialize; a type the handler publishes derives Serialize as well. The media type is application/json, and the generated AsyncAPI document reports it for each message. A payload that is not JSON, or JSON of another shape, is a decode failure, settled by the subscriber's failure policy. To name JSON where another codec is the scope's, mount through a router or a registration that names it, as on Codecs.

Example

The example builds with JSON as the only codec:

cargo test --example codec_json --no-default-features --features testing,macros,memory,json

Macros

examples/codec_json.rs

#[subscriber("orders")]
async fn bill(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "billed");
    HandlerOutcome::ack()
}

fn app() -> impl App {
    // No codec named anywhere: the handler decodes with the default codec, JSON.
    RustStream::new(AppInfo::new("billing", "0.1.0")).with_broker(MemoryBroker::new(), |b| {
        b.include(bill);
    })
}

Manual

examples/manual/codec_json.rs

struct Bill;

impl Handle<Order> for Bill {
    fn handle(
        &self,
        order: &Order,
        _outs: &(),
        _ctx: &mut Context<'_>,
    ) -> impl Future<Output = Result<(), HandlerOutcome>> {
        tracing::info!(order.id, "billed");
        ready(Ok(()))
    }
}

fn app() -> impl App {
    // No codec named anywhere: the registration decodes with the default codec, JSON.
    RustStream::new(AppInfo::new("billing", "0.1.0")).with_broker(MemoryBroker::new(), |b| {
        b.include(subscriber("orders", Bill).build());
    })
}