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/*
 * Copyright 2015 The gRPC Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.grpc;

import com.google.common.base.Preconditions;
import java.util.concurrent.TimeoutException;

/**
 * Utility methods for working with {@link Context}s in GRPC.
 */
public final class Contexts {

  private Contexts() {
  }

  /**
   * Make the provided {@link Context} {@link Context#current()} for the creation of a listener
   * to a received call and for all events received by that listener.
   *
   * 

This utility is expected to be used by {@link ServerInterceptor} implementations that need * to augment the {@link Context} in which the application does work when receiving events from * the client. * * @param context to make {@link Context#current()}. * @param call used to send responses to client. * @param headers received from client. * @param next handler used to create the listener to be wrapped. * @return listener that will receive events in the scope of the provided context. */ public static ServerCall.Listener interceptCall( Context context, ServerCall call, Metadata headers, ServerCallHandler next) { Context previous = context.attach(); try { return new ContextualizedServerCallListener<>( next.startCall(call, headers), context); } finally { context.detach(previous); } } /** * Implementation of {@link io.grpc.ForwardingServerCallListener} that attaches a context before * dispatching calls to the delegate and detaches them after the call completes. */ private static class ContextualizedServerCallListener extends ForwardingServerCallListener.SimpleForwardingServerCallListener { private final Context context; public ContextualizedServerCallListener(ServerCall.Listener delegate, Context context) { super(delegate); this.context = context; } @Override public void onMessage(ReqT message) { Context previous = context.attach(); try { super.onMessage(message); } finally { context.detach(previous); } } @Override public void onHalfClose() { Context previous = context.attach(); try { super.onHalfClose(); } finally { context.detach(previous); } } @Override public void onCancel() { Context previous = context.attach(); try { super.onCancel(); } finally { context.detach(previous); } } @Override public void onComplete() { Context previous = context.attach(); try { super.onComplete(); } finally { context.detach(previous); } } @Override public void onReady() { Context previous = context.attach(); try { super.onReady(); } finally { context.detach(previous); } } } /** * Returns the {@link Status} of a cancelled context or {@code null} if the context * is not cancelled. */ @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1975") public static Status statusFromCancelled(Context context) { Preconditions.checkNotNull(context, "context must not be null"); if (!context.isCancelled()) { return null; } Throwable cancellationCause = context.cancellationCause(); if (cancellationCause == null) { return Status.CANCELLED.withDescription("io.grpc.Context was cancelled without error"); } if (cancellationCause instanceof TimeoutException) { return Status.DEADLINE_EXCEEDED .withDescription(cancellationCause.getMessage()) .withCause(cancellationCause); } Status status = Status.fromThrowable(cancellationCause); if (Status.Code.UNKNOWN.equals(status.getCode()) && status.getCause() == cancellationCause) { // If fromThrowable could not determine a status, then // just return CANCELLED. return Status.CANCELLED.withDescription("Context cancelled").withCause(cancellationCause); } return status.withCause(cancellationCause); } }





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