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.lib.wsrs;
020    
021    import org.apache.hadoop.classification.InterfaceAudience;
022    
023    import java.text.MessageFormat;
024    
025    @InterfaceAudience.Private
026    public abstract class Param<T> {
027      private String name;
028      protected T value;
029    
030      public Param(String name, T defaultValue) {
031        this.name = name;
032        this.value = defaultValue;
033      }
034    
035      public String getName() {
036        return name;
037      }
038    
039      public T parseParam(String str) {
040        try {
041          value = (str != null && str.trim().length() > 0) ? parse(str) : value;
042        } catch (Exception ex) {
043          throw new IllegalArgumentException(
044            MessageFormat.format("Parameter [{0}], invalid value [{1}], value must be [{2}]",
045                                 name, str, getDomain()));
046        }
047        return value;
048      }
049    
050      public T value() {
051        return value;
052      }
053    
054      protected abstract String getDomain();
055    
056      protected abstract T parse(String str) throws Exception;
057    
058      @Override
059      public String toString() {
060        return (value != null) ? value.toString() : "NULL";
061      }
062    
063    }