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.hdfs.util;
020
021 import org.apache.hadoop.classification.InterfaceAudience;
022 import org.apache.hadoop.classification.InterfaceStability;
023 import org.xml.sax.ContentHandler;
024 import org.xml.sax.SAXException;
025 import org.xml.sax.helpers.AttributesImpl;
026
027 import java.util.LinkedList;
028 import java.util.List;
029 import java.util.Map;
030 import java.util.TreeMap;
031
032 /**
033 * General xml utilities.
034 *
035 */
036 @InterfaceAudience.Private
037 @InterfaceStability.Unstable
038 public class XMLUtils {
039 /**
040 * Exception that reflects an invalid XML document.
041 */
042 static public class InvalidXmlException extends RuntimeException {
043 private static final long serialVersionUID = 1L;
044 public InvalidXmlException(String s) {
045 super(s);
046 }
047 }
048
049 /**
050 * Add a SAX tag with a string inside.
051 *
052 * @param contentHandler the SAX content handler
053 * @param tag the element tag to use
054 * @param value the string to put inside the tag
055 */
056 public static void addSaxString(ContentHandler contentHandler,
057 String tag, String val) throws SAXException {
058 contentHandler.startElement("", "", tag, new AttributesImpl());
059 char c[] = val.toString().toCharArray();
060 contentHandler.characters(c, 0, c.length);
061 contentHandler.endElement("", "", tag);
062 }
063
064 /**
065 * Represents a bag of key-value pairs encountered during parsing an XML
066 * file.
067 */
068 static public class Stanza {
069 private TreeMap<String, LinkedList <Stanza > > subtrees;
070 private String value;
071
072 public Stanza() {
073 subtrees = new TreeMap<String, LinkedList <Stanza > >();
074 value = "";
075 }
076
077 public void setValue(String value) {
078 this.value = value;
079 }
080
081 public String getValue() {
082 return this.value;
083 }
084
085 /**
086 * Discover if a stanza has a given entry.
087 *
088 * @param name entry to look for
089 *
090 * @return true if the entry was found
091 */
092 public boolean hasChildren(String name) {
093 return subtrees.containsKey(name);
094 }
095
096 /**
097 * Pull an entry from a stanza.
098 *
099 * @param name entry to look for
100 *
101 * @return the entry
102 */
103 public List<Stanza> getChildren(String name) throws InvalidXmlException {
104 LinkedList <Stanza> children = subtrees.get(name);
105 if (children == null) {
106 throw new InvalidXmlException("no entry found for " + name);
107 }
108 return children;
109 }
110
111 /**
112 * Pull a string entry from a stanza.
113 *
114 * @param name entry to look for
115 *
116 * @return the entry
117 */
118 public String getValue(String name) throws InvalidXmlException {
119 if (!subtrees.containsKey(name)) {
120 throw new InvalidXmlException("no entry found for " + name);
121 }
122 LinkedList <Stanza> l = subtrees.get(name);
123 if (l.size() != 1) {
124 throw new InvalidXmlException("More than one value found for " + name);
125 }
126 return l.get(0).getValue();
127 }
128
129 /**
130 * Add an entry to a stanza.
131 *
132 * @param name name of the entry to add
133 * @param child the entry to add
134 */
135 public void addChild(String name, Stanza child) {
136 LinkedList<Stanza> l;
137 if (subtrees.containsKey(name)) {
138 l = subtrees.get(name);
139 } else {
140 l = new LinkedList<Stanza>();
141 subtrees.put(name, l);
142 }
143 l.add(child);
144 }
145
146 /**
147 * Convert a stanza to a human-readable string.
148 */
149 public String toString() {
150 StringBuilder bld = new StringBuilder();
151 bld.append("{");
152 if (!value.equals("")) {
153 bld.append("\"").append(value).append("\"");
154 }
155 String prefix = "";
156 for (Map.Entry<String, LinkedList <Stanza > > entry :
157 subtrees.entrySet()) {
158 String key = entry.getKey();
159 LinkedList <Stanza > ll = entry.getValue();
160 for (Stanza child : ll) {
161 bld.append(prefix);
162 bld.append("<").append(key).append(">");
163 bld.append(child.toString());
164 prefix = ", ";
165 }
166 }
167 bld.append("}");
168 return bld.toString();
169 }
170 }
171 }