io.grpc

Class ServerCall<ReqT,RespT>

java.lang.Object

io.grpc.ServerCall<ReqT,RespT>

Type Parameters:

ReqT - parsed type of request message.

RespT - parsed type of response message.

Direct Known Subclasses:

ForwardingServerCall

public abstract class ServerCall<ReqT,RespT>
extends Object

Encapsulates a single call received from a remote client. Calls may not simply be unary request-response even though this is the most common pattern. Calls may stream any number of requests and responses. This API is generally intended for use by generated handlers, but applications may use it directly if they need to.

Headers must be sent before any messages, which must be sent before closing.

No generic method for determining message receipt or providing acknowledgement is provided. Applications are expected to utilize normal messages for such signals, as a response naturally acknowledges its request.

Methods are guaranteed to be non-blocking. Implementations are not required to be thread-safe.

DO NOT MOCK: Use InProcessTransport and make a fake server instead.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ServerCall.Listener<ReqT> Callbacks for consuming incoming RPC messages.

Constructor Summary

Constructors

Constructor and Description
ServerCall()

Method Summary

Modifier and Type	Method and Description
abstract void	close(Status status, Metadata trailers) Close the call with the provided status.
Attributes	getAttributes() Returns properties of a single call.
String	getAuthority() Gets the authority this call is addressed to.
abstract MethodDescriptor<ReqT,RespT>	getMethodDescriptor() The MethodDescriptor for the call.
SecurityLevel	getSecurityLevel() Returns the level of security guarantee in communications
abstract boolean	isCancelled() Returns true when the call is cancelled and the server is encouraged to abort processing to save resources, since the client will not be processing any further methods.
boolean	isReady() If true, indicates that the call is capable of sending additional messages without requiring excessive buffering internally.
abstract void	request(int numMessages) Requests up to the given number of messages from the call to be delivered to ServerCall.Listener.onMessage(Object).
abstract void	sendHeaders(Metadata headers) Send response header metadata prior to sending a response message.
abstract void	sendMessage(RespT message) Send a response message.
void	setCompression(String compressor) Sets the compression algorithm for this call.
void	setMessageCompression(boolean enabled) Enables per-message compression, if an encoding type has been negotiated.

Methods inherited from class java.lang.Object

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

Constructor Detail

ServerCall

public ServerCall()

Method Detail

request

public abstract void request(int numMessages)

Requests up to the given number of messages from the call to be delivered to ServerCall.Listener.onMessage(Object). Once numMessages have been delivered no further request messages will be delivered until more messages are requested by calling this method again.

Servers use this mechanism to provide back-pressure to the client for flow-control.

This method is safe to call from multiple threads without external synchronization.

Parameters:

numMessages - the requested number of messages to be delivered to the listener.

sendHeaders

public abstract void sendHeaders(Metadata headers)

Send response header metadata prior to sending a response message. This method may only be called once and cannot be called after calls to sendMessage(RespT) or close(io.grpc.Status, io.grpc.Metadata).

Since Metadata is not thread-safe, the caller must not access (read or write) headers after this point.

Parameters:

headers - metadata to send prior to any response body.

Throws:

IllegalStateException - if close has been called, a message has been sent, or headers have already been sent

sendMessage

public abstract void sendMessage(RespT message)

Send a response message. Messages are the primary form of communication associated with RPCs. Multiple response messages may exist for streaming calls.

Parameters:

message - response message.

Throws:

IllegalStateException - if headers not sent or call is close(io.grpc.Status, io.grpc.Metadata)d

isReady

public boolean isReady()

If true, indicates that the call is capable of sending additional messages without requiring excessive buffering internally. This event is just a suggestion and the application is free to ignore it, however doing so may result in excessive buffering within the call.

If false, ServerCall.Listener.onReady() will be called after isReady() transitions to true.

This abstract class's implementation always returns true. Implementations generally override the method.

close

public abstract void close(Status status,
                           Metadata trailers)

Close the call with the provided status. No further sending or receiving will occur. If Status.isOk() is false, then the call is said to have failed.

If no errors or cancellations are known to have occurred, then a ServerCall.Listener.onComplete() notification should be expected, independent of status. Otherwise ServerCall.Listener.onCancel() has been or will be called.

Since Metadata is not thread-safe, the caller must not access (read or write) trailers after this point.

This method implies the caller completed processing the RPC, but it does not imply the RPC is complete. The call implementation will need additional time to complete the RPC and during this time the client is still able to cancel the request or a network error might cause the RPC to fail. If you wish to know when the call is actually completed/closed, you have to use ServerCall.Listener.onComplete() or ServerCall.Listener.onCancel() instead. This method is not necessarily invoked when Listener.onCancel() is called.

Throws:

IllegalStateException - if call is already closed

isCancelled

public abstract boolean isCancelled()

Returns true when the call is cancelled and the server is encouraged to abort processing to save resources, since the client will not be processing any further methods. Cancellations can be caused by timeouts, explicit cancel by client, network errors, and similar.

This method may safely be called concurrently from multiple threads.

setMessageCompression

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/1704")
public void setMessageCompression(boolean enabled)

Enables per-message compression, if an encoding type has been negotiated. If no message encoding has been negotiated, this is a no-op. By default per-message compression is enabled, but may not have any effect if compression is not enabled on the call.

setCompression

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/1704")
public void setCompression(String compressor)

Sets the compression algorithm for this call. If the server does not support the compression algorithm, the call will fail. This method may only be called before sendHeaders(io.grpc.Metadata). The compressor to use will be looked up in the CompressorRegistry. Default gRPC servers support the "gzip" compressor.

It is safe to call this even if the client does not support the compression format chosen. The implementation will handle negotiation with the client and may fall back to no compression.

Parameters:

compressor - the name of the compressor to use.

Throws:

IllegalArgumentException - if the compressor name can not be found.

getSecurityLevel

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/4692")
public SecurityLevel getSecurityLevel()

Returns the level of security guarantee in communications

Determining the level of security offered by the transport for RPCs on server-side. This can be approximated by looking for the SSLSession, but that doesn't work for ALTS and maybe some future TLS approaches. May return a lower security level when it cannot be determined precisely.

Returns:

non-null SecurityLevel enum

getAttributes

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/1779")
 @Grpc.TransportAttr
public Attributes getAttributes()

Returns properties of a single call.

Attributes originate from the transport and can be altered by ServerTransportFilter.

Returns:

non-null Attributes container

getAuthority

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/2924")
 @Nullable
public String getAuthority()

Gets the authority this call is addressed to.

Returns:

the authority string. null if not available.

getMethodDescriptor

public abstract MethodDescriptor<ReqT,RespT> getMethodDescriptor()

The MethodDescriptor for the call.