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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements. See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache license, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License. You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the license for the specific language governing permissions and
    15   * limitations under the license.
    16   */
    17  package org.apache.logging.log4j.core.lookup;
    18
    19  import org.apache.logging.log4j.Logger;
    20  import org.apache.logging.log4j.Marker;
    21  import org.apache.logging.log4j.MarkerManager;
    22  import org.apache.logging.log4j.core.LogEvent;
    23  import org.apache.logging.log4j.core.config.plugins.Plugin;
    24  import org.apache.logging.log4j.status.StatusLogger;
    25
    26  /**
    27   * Looks up keys from system properties.
    28   */
    29  @Plugin(name = "sys", category = StrLookup.CATEGORY)
    30  public class SystemPropertiesLookup extends AbstractLookup {
    31
    32      private static final Logger LOGGER = StatusLogger.getLogger();
    33      private static final Marker LOOKUP = MarkerManager.getMarker("LOOKUP");
    34
    35      /**
    36       * Looks up the value for the key using the data in the LogEvent.
    37       * @param event The current LogEvent.
    38       * @param key  the key to be looked up, may be null
    39       * @return The value associated with the key.
    40       */
    41      @Override
    42      public String lookup(final LogEvent event, final String key) {
    43          try {
    44              return System.getProperty(key);
    45          } catch (final Exception ex) {
    46              LOGGER.warn(LOOKUP, "Error while getting system property [{}].", key, ex);
    47              return null;
    48          }
    49      }
    50  }