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.util;
020    
021    import org.apache.hadoop.conf.Configuration;
022    import org.w3c.dom.DOMException;
023    import org.w3c.dom.Document;
024    import org.w3c.dom.Element;
025    import org.w3c.dom.Node;
026    import org.w3c.dom.NodeList;
027    import org.w3c.dom.Text;
028    import org.xml.sax.SAXException;
029    
030    import javax.xml.parsers.DocumentBuilder;
031    import javax.xml.parsers.DocumentBuilderFactory;
032    import javax.xml.parsers.ParserConfigurationException;
033    import java.io.IOException;
034    import java.io.InputStream;
035    import java.util.Map;
036    
037    /**
038     * Configuration utilities.
039     */
040    public abstract class ConfigurationUtils {
041    
042      /**
043       * Copy configuration key/value pairs from one configuration to another if a property exists in the target, it gets
044       * replaced.
045       *
046       * @param source source configuration.
047       * @param target target configuration.
048       */
049      public static void copy(Configuration source, Configuration target) {
050        Check.notNull(source, "source");
051        Check.notNull(target, "target");
052        for (Map.Entry<String, String> entry : source) {
053          target.set(entry.getKey(), entry.getValue());
054        }
055      }
056    
057      /**
058       * Injects configuration key/value pairs from one configuration to another if the key does not exist in the target
059       * configuration.
060       *
061       * @param source source configuration.
062       * @param target target configuration.
063       */
064      public static void injectDefaults(Configuration source, Configuration target) {
065        Check.notNull(source, "source");
066        Check.notNull(target, "target");
067        for (Map.Entry<String, String> entry : source) {
068          if (target.get(entry.getKey()) == null) {
069            target.set(entry.getKey(), entry.getValue());
070          }
071        }
072      }
073    
074      /**
075       * Returns a new ConfigurationUtils instance with all inline values resolved.
076       *
077       * @return a new ConfigurationUtils instance with all inline values resolved.
078       */
079      public static Configuration resolve(Configuration conf) {
080        Configuration resolved = new Configuration(false);
081        for (Map.Entry<String, String> entry : conf) {
082          resolved.set(entry.getKey(), conf.get(entry.getKey()));
083        }
084        return resolved;
085      }
086    
087      // Canibalized from FileSystemAccess <code>Configuration.loadResource()</code>.
088    
089      /**
090       * Create a configuration from an InputStream.
091       * <p/>
092       * ERROR canibalized from <code>Configuration.loadResource()</code>.
093       *
094       * @param is inputstream to read the configuration from.
095       *
096       * @throws IOException thrown if the configuration could not be read.
097       */
098      public static void load(Configuration conf, InputStream is) throws IOException {
099        try {
100          DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
101          // ignore all comments inside the xml file
102          docBuilderFactory.setIgnoringComments(true);
103          DocumentBuilder builder = docBuilderFactory.newDocumentBuilder();
104          Document doc = builder.parse(is);
105          parseDocument(conf, doc);
106        } catch (SAXException e) {
107          throw new IOException(e);
108        } catch (ParserConfigurationException e) {
109          throw new IOException(e);
110        }
111      }
112    
113      // Canibalized from FileSystemAccess <code>Configuration.loadResource()</code>.
114      private static void parseDocument(Configuration conf, Document doc) throws IOException {
115        try {
116          Element root = doc.getDocumentElement();
117          if (!"configuration".equals(root.getTagName())) {
118            throw new IOException("bad conf file: top-level element not <configuration>");
119          }
120          NodeList props = root.getChildNodes();
121          for (int i = 0; i < props.getLength(); i++) {
122            Node propNode = props.item(i);
123            if (!(propNode instanceof Element)) {
124              continue;
125            }
126            Element prop = (Element) propNode;
127            if (!"property".equals(prop.getTagName())) {
128              throw new IOException("bad conf file: element not <property>");
129            }
130            NodeList fields = prop.getChildNodes();
131            String attr = null;
132            String value = null;
133            for (int j = 0; j < fields.getLength(); j++) {
134              Node fieldNode = fields.item(j);
135              if (!(fieldNode instanceof Element)) {
136                continue;
137              }
138              Element field = (Element) fieldNode;
139              if ("name".equals(field.getTagName()) && field.hasChildNodes()) {
140                attr = ((Text) field.getFirstChild()).getData().trim();
141              }
142              if ("value".equals(field.getTagName()) && field.hasChildNodes()) {
143                value = ((Text) field.getFirstChild()).getData();
144              }
145            }
146    
147            if (attr != null && value != null) {
148              conf.set(attr, value);
149            }
150          }
151    
152        } catch (DOMException e) {
153          throw new IOException(e);
154        }
155      }
156    
157    }