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, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.conf;
020    
021    import java.util.Map;
022    import java.util.Collection;
023    import java.util.HashMap;
024    
025    public class ReconfigurationUtil {
026    
027      public static class PropertyChange {
028        public String prop;
029        public String oldVal;
030        public String newVal;
031    
032        public PropertyChange(String prop, String newVal, String oldVal) {
033          this.prop = prop;
034          this.newVal = newVal;
035          this.oldVal = oldVal;
036        }
037      }
038    
039      public static Collection<PropertyChange> 
040        getChangedProperties(Configuration newConf, Configuration oldConf) {
041        Map<String, PropertyChange> changes = new HashMap<String, PropertyChange>();
042    
043        // iterate over old configuration
044        for (Map.Entry<String, String> oldEntry: oldConf) {
045          String prop = oldEntry.getKey();
046          String oldVal = oldEntry.getValue();
047          String newVal = newConf.getRaw(prop);
048          
049          if (newVal == null || !newVal.equals(oldVal)) {
050            changes.put(prop, new PropertyChange(prop, newVal, oldVal));
051          }
052        }
053        
054        // now iterate over new configuration
055        // (to look for properties not present in old conf)
056        for (Map.Entry<String, String> newEntry: newConf) {
057          String prop = newEntry.getKey();
058          String newVal = newEntry.getValue();
059          if (oldConf.get(prop) == null) {
060            changes.put(prop, new PropertyChange(prop, newVal, null));
061          }
062        } 
063    
064        return changes.values();
065      }
066    
067      public Collection<PropertyChange> parseChangedProperties(
068          Configuration newConf, Configuration oldConf) {
069        return getChangedProperties(newConf, oldConf);
070      }
071    }