public interface RpcController
RpcController mediates a single method call. The primary purpose of the controller is
to provide a way to manipulate settings specific to the RPC implementation and to find out about
Starting with version 2.3.0, RPC implementations should not try to build on this, but should instead provide code generator plugins which generate code specific to the particular RPC implementation. This way the generated code can be more appropriate for the implementation in use and can avoid unnecessary layers of indirection.
The methods provided by the
RpcController interface are intended to be a "least common
denominator" set of features which we expect all implementations to support. Specific
implementations may provide more advanced features (e.g. deadline propagation).
public abstract String errorText()
true, returns a human-readable description of the error.
public abstract boolean failed()
After a call has finished, returns true if the call failed. The possible reasons for failure
depend on the RPC implementation.
failed() most only be called on the client side, and
must not be called before a call has finished.
public abstract boolean isCanceled()
true, indicates that the client canceled the RPC, so the server may as well give up
on replying to it. This method must be called on the server side only. The server should still
call the final "done" callback.
public abstract void notifyOnCancel(RpcCallback<Object> callback)
Asks that the given callback be called when the RPC is canceled. The parameter passed to the
callback will always be
null. The callback will always be called exactly once. If the
RPC completes without being canceled, the callback will be called after completion. If the RPC
has already been canceled when NotifyOnCancel() is called, the callback will be called
notifyOnCancel() must be called no more than once per request. It must be called on
the server side only.
public abstract void reset()
Resets the RpcController to its initial state so that it may be reused in a new call. This can be called from the client side only. It must not be called while an RPC is in progress.
public abstract void setFailed(String reason)
failed() to return true on the client side.
reason will be incorporated
into the message returned by
errorText(). If you find you need to return
machine-readable information about failures, you should incorporate it into your response
protocol buffer and should NOT call
public abstract void startCancel()
Advises the RPC system that the caller desires that the RPC call be canceled. The RPC system may cancel it immediately, may wait awhile and then cancel it, or may not even cancel the call at all. If the call is canceled, the "done" callback will still be called and the RpcController will indicate that the call failed at that time.