Package org.mockserver.grpc

Class GrpcWebTranslator

java.lang.Object

org.mockserver.grpc.GrpcWebTranslator

public class GrpcWebTranslator
extends Object

Translates between gRPC-Web framing and standard gRPC framing.

gRPC-Web uses the same length-prefixed message framing as gRPC but differs in two ways:

• Trailers-in-body: gRPC status trailers are sent as a special frame with flag byte 0x80 followed by ASCII-encoded trailer lines (grpc-status: N\r\ngrpc-message: ...\r\n)
• Base64 encoding (-text variant): when the content-type is application/grpc-web-text, the entire body (message frames + trailer frame) is base64-encoded

This class provides the conversion layer so gRPC-Web requests can be fed into the existing gRPC pipeline unchanged and gRPC responses can be re-framed as gRPC-Web.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	GRPC_WEB_CONTENT_TYPE
static final String	GRPC_WEB_PROTO_CONTENT_TYPE
static final String	GRPC_WEB_TEXT_CONTENT_TYPE
static final String	GRPC_WEB_TEXT_PROTO_CONTENT_TYPE
static final byte	TRAILER_FLAG	The flag byte that marks a trailer frame in gRPC-Web.

Constructor Summary

Constructors

Constructor	Description
GrpcWebTranslator()

Method Summary

Modifier and Type	Method	Description
static byte[]	buildTrailerFrame(String grpcStatus, String grpcMessage)	Builds a gRPC-Web trailer frame: flag byte 0x80, 4-byte length, then ASCII-encoded trailer lines.
static byte[]	decodeRequestBody(byte[] body, String contentType)	Decodes the request body from gRPC-Web framing to standard gRPC framing.
static byte[]	encodeResponseBody(byte[] messageFrameBody, String grpcStatus, String grpcMessage, boolean isTextVariant)	Builds a gRPC-Web response body from a standard gRPC response.
static boolean	isGrpcWebContentType(String contentType)	Returns true if the content-type indicates a gRPC-Web request (binary or text variant).
static boolean	isGrpcWebTextContentType(String contentType)	Returns true if the content-type is the base64-encoded text variant.
static String	parseTrailerFrame(byte[] trailerBody)	Parses trailers from a gRPC-Web trailer frame body.
static String	responseContentType(String requestContentType)	Returns the appropriate gRPC-Web response content-type based on the original request content-type.

Methods inherited from class java.lang.Object

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

Field Details

GRPC_WEB_CONTENT_TYPE

public static final String GRPC_WEB_CONTENT_TYPE

See Also:

• Constant Field Values

GRPC_WEB_PROTO_CONTENT_TYPE

public static final String GRPC_WEB_PROTO_CONTENT_TYPE

See Also:

• Constant Field Values

GRPC_WEB_TEXT_CONTENT_TYPE

public static final String GRPC_WEB_TEXT_CONTENT_TYPE

See Also:

• Constant Field Values

GRPC_WEB_TEXT_PROTO_CONTENT_TYPE

public static final String GRPC_WEB_TEXT_PROTO_CONTENT_TYPE

See Also:

• Constant Field Values

TRAILER_FLAG

public static final byte TRAILER_FLAG

The flag byte that marks a trailer frame in gRPC-Web.

See Also:

• Constant Field Values

Constructor Details

GrpcWebTranslator

public GrpcWebTranslator()

Method Details

isGrpcWebContentType

public static boolean isGrpcWebContentType(String contentType)

Returns true if the content-type indicates a gRPC-Web request (binary or text variant).

isGrpcWebTextContentType

public static boolean isGrpcWebTextContentType(String contentType)

Returns true if the content-type is the base64-encoded text variant.

decodeRequestBody

public static byte[] decodeRequestBody(byte[] body,
 String contentType)

Decodes the request body from gRPC-Web framing to standard gRPC framing. For the -text variant, the body is base64-decoded first. The returned bytes are standard gRPC length-prefixed message frames that can be fed directly into GrpcFrameCodec.decode(byte[]).

Parameters:

body - the raw request body

contentType - the content-type header value

Returns:

standard gRPC-framed message bytes

encodeResponseBody

public static byte[] encodeResponseBody(byte[] messageFrameBody,
 String grpcStatus,
 String grpcMessage,
 boolean isTextVariant)

Builds a gRPC-Web response body from a standard gRPC response.

The response consists of message frame(s) followed by a trailer frame (flag 0x80) containing the grpc-status and optional grpc-message as ASCII lines.

Parameters:

messageFrameBody - the gRPC-framed message body (may be empty/null)

grpcStatus - the gRPC status code as a string (e.g. "0")

grpcMessage - the gRPC status message (may be null)

isTextVariant - if true, the entire body is base64-encoded

Returns:

the gRPC-Web response body bytes

buildTrailerFrame

public static byte[] buildTrailerFrame(String grpcStatus,
 String grpcMessage)

Builds a gRPC-Web trailer frame: flag byte 0x80, 4-byte length, then ASCII-encoded trailer lines.

parseTrailerFrame

public static String parseTrailerFrame(byte[] trailerBody)

Parses trailers from a gRPC-Web trailer frame body. The trailer frame body is the ASCII text after the 5-byte header.

Parameters:

trailerBody - the raw trailer body bytes (without the 5-byte frame header)

Returns:

parsed trailer lines as a string

responseContentType

public static String responseContentType(String requestContentType)

Returns the appropriate gRPC-Web response content-type based on the original request content-type.

Parameters:

requestContentType - the original gRPC-Web request content-type

Returns:

the matching gRPC-Web response content-type