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 org.apache.beam.examples.webapis;
  
  import java.time.Instant;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.ParDo;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /** {@link Log} has convenience {@link DoFn}s for logging output. */
  class Log {
    private static final Logger LOG = LoggerFactory.getLogger(Log.class);
  
    /** Logs output to stderr. */
    static <T> ParDo.SingleOutput<T, T> errorOf() {
      return ParDo.of(new LogErrorFn<>());
    }
  
    /** Logs output to stdout. */
    static <T> ParDo.SingleOutput<T, T> infoOf() {
      return ParDo.of(new LogInfoFn<>());
    }
  
    private static class LogErrorFn<T> extends DoFn<T, T> {
      @ProcessElement
      public void process(@Element T element, OutputReceiver<T> receiver) {
        LOG.error("{}: {}", Instant.now(), element);
        receiver.output(element);
      }
    }
  
    private static class LogInfoFn<T> extends DoFn<T, T> {
  
      @ProcessElement
      public void process(@Element T element, OutputReceiver<T> receiver) {
        LOG.info("{}: {}", Instant.now(), element);
        receiver.output(element);
      }
    }
  }
  