public final class GrpcWeb

Object
GrpcWeb

High-level gRPC-Web invoker used by generated @GrpcClient implementations. Handles HTTP-level transport, gRPC-Web payload framing (flags + length + payload), and trailer parsing (grpc-status, grpc-message).

Wire details (from the upstream gRPC-Web spec):

URL: <baseUrl>/<service-fqn>/<method-name> (no trailing slash).
HTTP method: POST.
Request Content-Type: application/grpc-web+proto.
Request headers: X-Grpc-Web: 1, X-User-Agent: grpc-web-cn1/<ver>.
Request body: 0x00 <length-be32> <payload> – one data frame.
Response body: zero or more data frames (flags low bit 0) followed by one trailer frame (flags high bit 0x80) carrying grpc-status:<n>\r\ngrpc-message:<text>\r\n.

All methods are static. Generated impls call invokeUnary and receive the parsed GrpcResponse on the supplied callback.

Fields

`public static final` `String CONTENT_TYPE = "application/grpc-web+proto"`	Content type for binary gRPC-Web payloads.
`public static final int FLAG_TRAILER = 128`	gRPC-Web frame flag set in the trailer frame’s first byte.

Methods

`public static <Req, Resp> void invokeUnary(String baseUrl, String service, String method, String bearerToken, Req request, ProtoCodec<Req> reqCodec, ProtoCodec<Resp> respCodec, OnComplete<GrpcResponse<Resp>> callback)`	Sends a unary gRPC-Web request and invokes `callback` with the decoded response (or a transport-failure marker).
`public static <T> byte[] frame(T request,` `ProtoCodec<T> codec) throws IOException`	Wraps a serialised request message in a single gRPC-Web data frame: `[0x00][length-be32][payload]`.
`public static <Resp>` `GrpcResponse<Resp> decode(byte[] response, int httpCode, ProtoCodec<Resp> respCodec)`	Decodes a complete gRPC-Web response body.

Inherited methods

From Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait, clone

Field details

CONTENT_TYPE

public static final String CONTENT_TYPE = "application/grpc-web+proto"

Content type for binary gRPC-Web payloads. The text variant (application/grpc-web-text, base64-encoded) is not supported – modern Envoy/gRPC-Web proxies all speak binary.

FLAG_TRAILER

public static final int FLAG_TRAILER = 128

gRPC-Web frame flag set in the trailer frame’s first byte.

Method details

invokeUnary

public static <Req, Resp> void invokeUnary(String baseUrl, String service, String method, String bearerToken, Req request, ProtoCodec<Req> reqCodec, ProtoCodec<Resp> respCodec, OnComplete<GrpcResponse<Resp>> callback)

Sends a unary gRPC-Web request and invokes callback with the decoded response (or a transport-failure marker).

The baseUrl should not include a trailing slash; the service is the fully qualified service path (e.g. helloworld.Greeter) and method is the gRPC method name (e.g. SayHello). The resulting URL is <baseUrl>/<service>/<method>.

frame

public static <T> byte[] frame(T request, ProtoCodec<T> codec)
throws IOException

Wraps a serialised request message in a single gRPC-Web data frame: [0x00][length-be32][payload]. Public so unit tests can verify framing independently of the network path.

Throws

IOException

decode

public static <Resp> GrpcResponse<Resp> decode(byte[] response, int httpCode, ProtoCodec<Resp> respCodec)

Decodes a complete gRPC-Web response body. Iterates frames, concatenates data payloads, and parses the trailer frame for grpc-status / grpc-message. Public so callers can replay canned responses in unit tests.