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 package org.apache.hadoop.hdfs.web.resources;
019
020 import java.io.UnsupportedEncodingException;
021 import java.net.URLEncoder;
022 import java.util.Arrays;
023 import java.util.Comparator;
024
025
026 /** Base class of parameters. */
027 public abstract class Param<T, D extends Param.Domain<T>> {
028 static final String NULL = "null";
029
030 static final Comparator<Param<?,?>> NAME_CMP = new Comparator<Param<?,?>>() {
031 @Override
032 public int compare(Param<?, ?> left, Param<?, ?> right) {
033 return left.getName().compareTo(right.getName());
034 }
035 };
036
037 /** Convert the parameters to a sorted String.
038 *
039 * @param separator URI parameter separator character
040 * @param parameters parameters to encode into a string
041 * @return the encoded URI string
042 */
043 public static String toSortedString(final String separator,
044 final Param<?, ?>... parameters) {
045 Arrays.sort(parameters, NAME_CMP);
046 final StringBuilder b = new StringBuilder();
047 try {
048 for(Param<?, ?> p : parameters) {
049 if (p.getValue() != null) {
050 b.append(separator).append(
051 URLEncoder.encode(p.getName(), "UTF-8")
052 + "="
053 + URLEncoder.encode(p.getValueString(), "UTF-8"));
054 }
055 }
056 } catch (UnsupportedEncodingException e) {
057 // Sane systems know about UTF-8, so this should never happen.
058 throw new RuntimeException(e);
059 }
060 return b.toString();
061 }
062
063 /** The domain of the parameter. */
064 final D domain;
065 /** The actual parameter value. */
066 final T value;
067
068 Param(final D domain, final T value) {
069 this.domain = domain;
070 this.value = value;
071 }
072
073 /** @return the parameter value. */
074 public final T getValue() {
075 return value;
076 }
077
078 /** @return the parameter value as a string */
079 public abstract String getValueString();
080
081 /** @return the parameter name. */
082 public abstract String getName();
083
084 @Override
085 public String toString() {
086 return getName() + "=" + value;
087 }
088
089 /** Base class of parameter domains. */
090 static abstract class Domain<T> {
091 /** Parameter name. */
092 final String paramName;
093
094 Domain(final String paramName) {
095 this.paramName = paramName;
096 }
097
098 /** @return the parameter name. */
099 public final String getParamName() {
100 return paramName;
101 }
102
103 /** @return a string description of the domain of the parameter. */
104 public abstract String getDomain();
105
106 /** @return the parameter value represented by the string. */
107 abstract T parse(String str);
108
109 /** Parse the given string.
110 * @return the parameter value represented by the string.
111 */
112 public final T parse(final String varName, final String str) {
113 try {
114 return str != null && str.trim().length() > 0 ? parse(str) : null;
115 } catch(Exception e) {
116 throw new IllegalArgumentException("Failed to parse \"" + str
117 + "\" for the parameter " + varName
118 + ". The value must be in the domain " + getDomain(), e);
119 }
120 }
121 }
122 }