Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.examples.utils.wake;
020
021import org.apache.reef.wake.EventHandler;
022
023import java.util.logging.Level;
024import java.util.logging.Logger;
025
026/**
027 * An EventHandler that logs its events before handing it to a downstream
028 * EventHandler.
029 *
030 * @param <T>
031 */
032public class LoggingEventHandler<T> implements EventHandler<T> {
033
034  private static final Logger LOG = Logger.getLogger(LoggingEventHandler.class.getName());
035
036  private final EventHandler<T> downstreamEventHandler;
037  private final String format;
038
039  /**
040   * @param downstreamEventHandler the event handler to hand the event to
041   * @param format                 Format string to log the event, e.g. "Event {0} received".
042   */
043  public LoggingEventHandler(final EventHandler<T> downstreamEventHandler, final String format) {
044    this.downstreamEventHandler = downstreamEventHandler;
045    this.format = format;
046  }
047
048  public LoggingEventHandler(final EventHandler<T> downstreamEventHandler) {
049    this(downstreamEventHandler, "{0}");
050  }
051
052  @Override
053  public void onNext(final T value) {
054    LOG.log(Level.INFO, this.format, value);
055    this.downstreamEventHandler.onNext(value);
056  }
057}