    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
    18  package org.apache.log4j;
    19
    20  import org.apache.log4j.util.Filter;
    21
    22  /**
    23   * This class switches MDC values into the order
    24   * (unreasonably) expected by the witness files.
    25   */
    26  public class MDCOrderFilter implements Filter {
    27
    28      /**
    29       * Unexpected orders of keys.
    30       * Note expected values are "va-one-one" and "va-one-two".
    31       */
    32    private static final String[] patterns =
    33            new String[] {
    34                    "{key2,va12}{key1,va11}",
    35                    "{key2,value2}{key1,value1}"
    36            };
    37
    38      /**
    39       * Replacement values.
    40       */
    41    private static final String[] replacements =
    42              new String[] {
    43                      "{key1,va11}{key2,va12}",
    44                      "{key1,value1}{key2,value2}"
    45              };
    46
    47    /**
    48     *  Switch order of MDC keys when not in expected order.
    49     */
    50    public String filter(final String in) {
    51      if (in == null) {
    52        return null;
    53      }
    54
    55      for(int i = 0; i < patterns.length; i++) {
    56          int ipos = in.indexOf(patterns[i]);
    57          if (ipos >= 1) {
    58              return in.substring(0, ipos)
    59                      + replacements[i]
    60                      + in.substring(ipos + patterns[i].length());
    61          }
    62      }
    63      return in;
    64    }
    65  }