DelegatorContext.java

/*
 * Copyright © 2014 Cask Data, Inc.
 *
 * 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 co.cask.cdap.internal.app.runtime.service.http;

import co.cask.cdap.api.service.http.HttpServiceContext;
import co.cask.cdap.api.service.http.HttpServiceHandler;
import org.apache.twill.common.Cancellable;

/**
 * Context object for carrying context information used by generated handler delegator classes.
 *
 * @param <T> Type of the user {@link HttpServiceHandler}
 */
public interface DelegatorContext<T extends HttpServiceHandler> {

  /**
   * Returns an instance of the user service handler.
   * Calling this method multiple times from the same thread will return
   * the same instance until {@link #capture()} is called.
   */
  T getHandler();

  /**
   * Returns an instance of the service context.
   * Calling this method multiple times from the same thread will return
   * the same instance until {@link #capture()} is called.
   */
  HttpServiceContext getServiceContext();

  /**
   * Capture the current context. Once this method is called, the current instances of
   * {@link HttpServiceHandler} and {@link HttpServiceContext} associated with the caller thread
   * will no longer be available through the {@link #getHandler()} or {@link #getServiceContext()} methods.
   *
   * @return a {@link Cancellable} to release the captured context so that the {@link HttpServiceHandler} and
   *         {@link HttpServiceContext} will be available for the caller thread of the {@link Cancellable#cancel()}
   *         to be reused.
   */
  Cancellable capture();
}