configuration.java

来自「Hadoop是一个用于运行应用程序在大型集群的廉价硬件设备上的框架。Hadoop」· Java 代码 · 共 483 行 · 第 1/2 页

   * An error is thrown if the returned class does not implement the named
   * interface. 
   */
  public Class getClass(String propertyName, Class defaultValue,Class xface) {
    try {
      Class theClass = getClass(propertyName, defaultValue);
      if (theClass != null && !xface.isAssignableFrom(theClass))
        throw new RuntimeException(theClass+" not "+xface.getName());
      return theClass;
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  /** Sets the value of the <code>name</code> property to the name of a class.
   * First checks that the class implements the named interface. 
   */
  public void setClass(String propertyName, Class theClass, Class xface) {
    if (!xface.isAssignableFrom(theClass))
      throw new RuntimeException(theClass+" not "+xface.getName());
    set(propertyName, theClass.getName());
  }

  /** Returns a file name under a directory named in <i>dirsProp</i> with the
   * given <i>path</i>.  If <i>dirsProp</i> contains multiple directories, then
   * one is chosen based on <i>path</i>'s hash code.  If the selected directory
   * does not exist, an attempt is made to create it.
   */
  public File getFile(String dirsProp, String path) throws IOException {
    String[] dirs = getStrings(dirsProp);
    int hashCode = path.hashCode();
    for (int i = 0; i < dirs.length; i++) {  // try each local dir
      int index = (hashCode+i & Integer.MAX_VALUE) % dirs.length;
      File file = new File(dirs[index], path).getAbsoluteFile();
      File dir = file.getParentFile();
      if (dir.exists() || dir.mkdirs()) {
        return file;
      }
    }
    throw new IOException("No valid local directories in property: "+dirsProp);
  }


  /** Returns the URL for the named resource. */
  public URL getResource(String name) {
    return classLoader.getResource(name);
  }
  /** Returns an input stream attached to the configuration resource with the
   * given <code>name</code>.
   */
  public InputStream getConfResourceAsInputStream(String name) {
    try {
      URL url= getResource(name);

      if (url == null) {
        LOG.info(name + " not found");
        return null;
      } else {
        LOG.info("found resource " + name + " at " + url);
      }

      return url.openStream();
    } catch (Exception e) {
      return null;
    }
  }

  /** Returns a reader attached to the configuration resource with the
   * given <code>name</code>.
   */
  public Reader getConfResourceAsReader(String name) {
    try {
      URL url= getResource(name);

      if (url == null) {
        LOG.info(name + " not found");
        return null;
      } else {
        LOG.info("found resource " + name + " at " + url);
      }

      return new InputStreamReader(url.openStream());
    } catch (Exception e) {
      return null;
    }
  }

  private synchronized Properties getProps() {
    if (properties == null) {
      Properties newProps = new Properties();
      loadResources(newProps, defaultResources, false, false);
      loadResources(newProps, finalResources, true, true);
      properties = newProps;
    }
    return properties;
  }

  private void loadResources(Properties props,
                             ArrayList resources,
                             boolean reverse, boolean quiet) {
    ListIterator i = resources.listIterator(reverse ? resources.size() : 0);
    while (reverse ? i.hasPrevious() : i.hasNext()) {
      loadResource(props, reverse ? i.previous() : i.next(), quiet);
    }
  }

  private void loadResource(Properties properties, Object name, boolean quiet) {
    try {
      DocumentBuilder builder =
        DocumentBuilderFactory.newInstance().newDocumentBuilder();
      Document doc = null;

      if (name instanceof String) {               // a CLASSPATH resource
        URL url = getResource((String)name);
        if (url != null) {
          LOG.info("parsing " + url);
          doc = builder.parse(url.toString());
        }
      } else if (name instanceof File) {          // a file resource
        File file = (File)name;
        if (file.exists()) {
          LOG.info("parsing " + file);
          doc = builder.parse(file);
        }
      }

      if (doc == null) {
        if (quiet)
          return;
        throw new RuntimeException(name + " not found");
      }

      Element root = doc.getDocumentElement();
      if (!"configuration".equals(root.getTagName()))
        LOG.severe("bad conf file: top-level element not <configuration>");
      NodeList props = root.getChildNodes();
      for (int i = 0; i < props.getLength(); i++) {
        Node propNode = props.item(i);
        if (!(propNode instanceof Element))
          continue;
        Element prop = (Element)propNode;
        if (!"property".equals(prop.getTagName()))
          LOG.warning("bad conf file: element not <property>");
        NodeList fields = prop.getChildNodes();
        String attr = null;
        String value = null;
        for (int j = 0; j < fields.getLength(); j++) {
          Node fieldNode = fields.item(j);
          if (!(fieldNode instanceof Element))
            continue;
          Element field = (Element)fieldNode;
          if ("name".equals(field.getTagName()))
            attr = ((Text)field.getFirstChild()).getData();
          if ("value".equals(field.getTagName()) && field.hasChildNodes())
            value = ((Text)field.getFirstChild()).getData();
        }
        if (attr != null && value != null)
          properties.setProperty(attr, value);
      }
        
    } catch (Exception e) {
      LOG.severe("error parsing conf file: " + e);
      throw new RuntimeException(e);
    }
    
  }

  /** Writes non-default properties in this configuration.*/
  public void write(OutputStream out) throws IOException {
    Properties properties = getProps();
    try {
      Document doc =
        DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
      Element conf = doc.createElement("configuration");
      doc.appendChild(conf);
      conf.appendChild(doc.createTextNode("\n"));
      for (Enumeration e = properties.keys(); e.hasMoreElements();) {
        String name = (String)e.nextElement();
        Object object = properties.get(name);
        String value = null;
        if(object instanceof String) {
          value = (String) object;
        }else {
          continue;
        }
        Element propNode = doc.createElement("property");
        conf.appendChild(propNode);
      
        Element nameNode = doc.createElement("name");
        nameNode.appendChild(doc.createTextNode(name));
        propNode.appendChild(nameNode);
      
        Element valueNode = doc.createElement("value");
        valueNode.appendChild(doc.createTextNode(value));
        propNode.appendChild(valueNode);

        conf.appendChild(doc.createTextNode("\n"));
      }
    
      DOMSource source = new DOMSource(doc);
      StreamResult result = new StreamResult(out);
      TransformerFactory transFactory = TransformerFactory.newInstance();
      Transformer transformer = transFactory.newTransformer();
      transformer.transform(source, result);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  public String toString() {
    StringBuffer sb = new StringBuffer();
    sb.append("Configuration: ");
    sb.append("defaults: ");
    toString(defaultResources, sb);
    sb.append("final: ");
    toString(finalResources, sb);
    return sb.toString();
  }

  private void toString(ArrayList resources, StringBuffer sb) {
    ListIterator i = resources.listIterator();
    while (i.hasNext()) {
      if (i.nextIndex() != 0) {
        sb.append(" , ");
      }
      Object obj = i.next();
      if (obj instanceof File) {
        sb.append((File)obj);
      } else {
        sb.append((String)obj);
      }
    }
  }

  /** For debugging.  List non-default properties to the terminal and exit. */
  public static void main(String[] args) throws Exception {
    new Configuration().write(System.out);
  }

}