content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 com.alibaba.jstorm.window;
  
  import backtype.storm.task.TopologyContext;
  import java.util.Collection;
  import java.util.Collections;
  
  /**
   * A {@link WindowAssigner} that windows elements into sessions based on the current processing
   * time.
   */
  public class ProcessingTimeSessionWindows<T> extends WindowAssigner<T> {
      private static final long serialVersionUID = 1L;
  
      protected long sessionTimeout;
  
      protected ProcessingTimeSessionWindows(long sessionTimeout) {
          this.sessionTimeout = sessionTimeout;
      }
  
      @Override
      public Collection<TimeWindow> assignWindows(Object element, long timestamp) {
          return Collections.singletonList(new TimeWindow(timestamp, timestamp + sessionTimeout));
      }
  
      @Override
      public Trigger<T> getDefaultTrigger(TopologyContext context) {
          return ProcessingTimeTrigger.create();
      }
  
      @Override
      public String toString() {
          return "ProcessingTimeSessionWindows(" + sessionTimeout + ")";
      }
  
      /**
       * Creates a new {@code SessionWindows} {@link WindowAssigner} that assigns
       * elements to sessions based on the element timestamp.
       *
       * @param timeout The session timeout, i.e. the time gap between sessions
       * @return The policy.
       */
      public static <T> ProcessingTimeSessionWindows<T> withGap(long timeout) {
          return new ProcessingTimeSessionWindows<>(timeout);
      }
  }
  