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
019package org.apache.hadoop.lib.wsrs;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022
023import java.text.MessageFormat;
024
025@InterfaceAudience.Private
026public 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}