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Netty based path router
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/*
 * 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.http;

/**
 *  Interface that needs to be implemented for handling HTTP methods. init and destroy methods can be used to manage
 *  the lifecycle of the object. The framework will call init and destroy during startup and shutdown respectively.
 *  No handles will be called before init method of the class is called or after the destroy method is called.
 *  The handlers should be annotated with Jax-RS annotations to handle appropriate path and HTTP Methods.
 *  Note: Only the annotations in the given handler object will be inspected and be available for routing. The
 *  annotations from the base class (if extended) will not be applied to the given handler object.
 *  Note: The framework that calls the handler assumes that the implementation is threadsafe.
 *  Note: If the HttpHandler implementation is extended, the annotations are not inherited from the base class.
 *
 *  Example:
 *  public class ApiHandler implements HttpHandler{
 *    {@literal @}Override
 *    public void init(HandlerContext context){
 *      //Perform bootstrap operations before any of the handlers in this class gets called.
 *    }
 *    {@literal @}Override
 *    public void destroy(HandlerContext context){
 *      //Perform teardown operations before the server shuts down.
 *    }
 *
 *    {@literal @}Path("/common/v1/widgets")
 *    {@literal @}GET
 *    public void handleGet(HttpRequest request, HttpResponder responder){
 *      //Handle Http request
 *    }
 *  }
 *
 */
public interface HttpHandler {

  /**
   * init method will be called before the netty pipeline is setup. Any initialization operation can be performed
   * in this method.
   *
   * @param context instance of HandlerContext.
   */
  void init(HandlerContext context);

  /**
   * destroy method will be called before shutdown. Any teardown task can be performed in this method.
   * At this point the server will not accept any more new requests.
   *
   * @param context instance of HandlerContext.
  */
  void destroy(HandlerContext context);
}