Class ServletAdapter

java.lang.Object

io.grpc.servlet.ServletAdapter

@ExperimentalApi("https://github.com/grpc/grpc-java/issues/5066")
public final class ServletAdapter
extends Object

An adapter that transforms HttpServletRequest into gRPC request and lets a gRPC server process it, and transforms the gRPC response into HttpServletResponse. An adapter can be instantiated by ServletServerBuilder.buildServletAdapter().

In a servlet, calling doPost(HttpServletRequest, HttpServletResponse) inside HttpServlet.doPost(HttpServletRequest, HttpServletResponse) makes the servlet backed by the gRPC server associated with the adapter. The servlet must support Asynchronous Processing and must be deployed to a container that supports servlet 4.0 and enables HTTP/2.

The API is experimental. The authors would like to know more about the real usecases. Users are welcome to provide feedback by commenting on the tracking issue.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final class	ServletAdapter.GrpcAsyncListener
private static final class	ServletAdapter.GrpcReadListener

Field Summary

Fields

Modifier and Type	Field	Description
private final Attributes	attributes
(package private) static final Logger	logger
private final int	maxInboundMessageSize
private final List<? extends ServerStreamTracer.Factory>	streamTracerFactories
private final ServerTransportListener	transportListener

Constructor Summary

Constructors

Constructor	Description
ServletAdapter(ServerTransportListener transportListener, List<? extends ServerStreamTracer.Factory> streamTracerFactories, int maxInboundMessageSize)

Method Summary

Modifier and Type	Method	Description
void	destroy()	Call this method when the adapter is no longer needed.
void	doGet(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp)	Call this method inside HttpServlet.doGet(HttpServletRequest, HttpServletResponse) to serve gRPC GET request.
void	doPost(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp)	Call this method inside HttpServlet.doPost(HttpServletRequest, HttpServletResponse) to serve gRPC POST request.
private static String	getAuthority(javax.servlet.http.HttpServletRequest req)
private static Metadata	getHeaders(javax.servlet.http.HttpServletRequest req)
static boolean	isGrpc(javax.servlet.http.HttpServletRequest request)	Checks whether an incoming HttpServletRequest may come from a gRPC client.

Methods inherited from class Object

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

Field Details

logger

static final Logger logger

transportListener

private final ServerTransportListener transportListener

streamTracerFactories

private final List<? extends ServerStreamTracer.Factory> streamTracerFactories

maxInboundMessageSize

private final int maxInboundMessageSize

attributes

private final Attributes attributes

Constructor Details

ServletAdapter

ServletAdapter(ServerTransportListener transportListener,
 List<? extends ServerStreamTracer.Factory> streamTracerFactories,
 int maxInboundMessageSize)

Method Details

doGet

public void doGet(javax.servlet.http.HttpServletRequest req,
 javax.servlet.http.HttpServletResponse resp)
           throws IOException

Call this method inside HttpServlet.doGet(HttpServletRequest, HttpServletResponse) to serve gRPC GET request.

This method is currently not implemented.

Note that in rare case gRPC client sends GET requests.

Do not modify req and resp before or after calling this method. However, calling resp.setBufferSize() before invocation is allowed.

Throws:

IOException

doPost

public void doPost(javax.servlet.http.HttpServletRequest req,
 javax.servlet.http.HttpServletResponse resp)
            throws IOException

Call this method inside HttpServlet.doPost(HttpServletRequest, HttpServletResponse) to serve gRPC POST request.

Do not modify req and resp before or after calling this method. However, calling resp.setBufferSize() before invocation is allowed.

Throws:

IOException

getHeaders

private static Metadata getHeaders(javax.servlet.http.HttpServletRequest req)

getAuthority

private static String getAuthority(javax.servlet.http.HttpServletRequest req)

destroy

public void destroy()

Call this method when the adapter is no longer needed. The gRPC server will be terminated.

isGrpc

public static boolean isGrpc(javax.servlet.http.HttpServletRequest request)

Checks whether an incoming HttpServletRequest may come from a gRPC client.

Returns:

true if the request comes from a gRPC client