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// Protocol Buffers - Google's data interchange format
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package com.google.protobuf;

/**
 * An {@code 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
 * RPC-level errors.
 *
 * 

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 {@code 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). * * @author [email protected] Kenton Varda */ public interface RpcController { // ----------------------------------------------------------------- // These calls may be made from the client side only. Their results // are undefined on the server side (may throw RuntimeExceptions). /** * 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. */ void reset(); /** * After a call has finished, returns true if the call failed. The possible reasons for failure * depend on the RPC implementation. {@code failed()} most only be called on the client side, and * must not be called before a call has finished. */ boolean failed(); /** If {@code failed()} is {@code true}, returns a human-readable description of the error. */ String errorText(); /** * 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. */ void startCancel(); // ----------------------------------------------------------------- // These calls may be made from the server side only. Their results // are undefined on the client side (may throw RuntimeExceptions). /** * Causes {@code failed()} to return true on the client side. {@code reason} will be incorporated * into the message returned by {@code 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 {@code setFailed()}. */ void setFailed(String reason); /** * If {@code 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. */ boolean isCanceled(); /** * Asks that the given callback be called when the RPC is canceled. The parameter passed to the * callback will always be {@code 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 * immediately. * *

{@code notifyOnCancel()} must be called no more than once per request. It must be called on * the server side only. */ void notifyOnCancel(RpcCallback callback); }