configuration.java

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/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.conf;

import java.util.*;
import java.net.URL;
import java.io.*;
import java.util.logging.Logger;

import javax.xml.parsers.*;

import org.w3c.dom.*;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.apache.hadoop.util.LogFormatter;

/** Provides access to configuration parameters.  Configurations are specified
 * by resources.  A resource contains a set of name/value pairs.
 *
 * <p>Each resources is named by either a String or by a File.  If named by a
 * String, then the classpath is examined for a file with that name.  If a
 * File, then the filesystem is examined directly, without referring to the
 * CLASSPATH.
 *
 * <p>Configuration resources are of two types: default and
 * final.  Default values are loaded first and final values are loaded last, and
 * thus override default values.
 *
 * <p>Hadoop's default resource is the String "hadoop-default.xml" and its
 * final resource is the String "hadoop-site.xml".  Other tools built on Hadoop
 * may specify additional resources.
 */
public class Configuration {
  private static final Logger LOG =
    LogFormatter.getLogger("org.apache.hadoop.conf.Configuration");

  private ArrayList defaultResources = new ArrayList();
  private ArrayList finalResources = new ArrayList();

  private Properties properties;
  private ClassLoader classLoader = 
    Thread.currentThread().getContextClassLoader();

  /** A new configuration. */
  public Configuration() {
    defaultResources.add("hadoop-default.xml");
    finalResources.add("hadoop-site.xml");
  }

  /** A new configuration with the same settings cloned from another. */
  public Configuration(Configuration other) {
    this.defaultResources = (ArrayList)other.defaultResources.clone();
    this.finalResources = (ArrayList)other.finalResources.clone();
    if (other.properties != null)
      this.properties = (Properties)other.properties.clone();
  }

  /** Add a default resource. */
  public void addDefaultResource(String name) {
    addResource(defaultResources, name);
  }

  /** Add a default resource. */
  public void addDefaultResource(File file) {
    addResource(defaultResources, file);
  }

  /** Add a final resource. */
  public void addFinalResource(String name) {
    addResource(finalResources, name);
  }

  /** Add a final resource. */
  public void addFinalResource(File file) {
    addResource(finalResources, file);
  }

  private synchronized void addResource(ArrayList resources, Object resource) {
    resources.add(resource);                      // add to resources
    properties = null;                            // trigger reload
  }
  
  /**
   * Returns the value of the <code>name</code> property, or null if no such
   * property exists.
   */
  public Object getObject(String name) { return getProps().get(name);}

  /** Sets the value of the <code>name</code> property. */
  public void setObject(String name, Object value) {
    getProps().put(name, value);
  }

  /** Returns the value of the <code>name</code> property.  If no such property
   * exists, then <code>defaultValue</code> is returned.
   */
  public Object get(String name, Object defaultValue) {
    Object res = getObject(name);
    if (res != null) return res;
    else return defaultValue;
  }
  
  /** Returns the value of the <code>name</code> property, or null if no
   * such property exists. */
  public String get(String name) { return getProps().getProperty(name);}

  /** Sets the value of the <code>name</code> property. */
  public void set(String name, Object value) {
    getProps().setProperty(name, value.toString());
  }
  
  /** Returns the value of the <code>name</code> property.  If no such property
   * exists, then <code>defaultValue</code> is returned.
   */
  public String get(String name, String defaultValue) {
     return getProps().getProperty(name, defaultValue);
  }
  
  /** Returns the value of the <code>name</code> property as an integer.  If no
   * such property is specified, or if the specified value is not a valid
   * integer, then <code>defaultValue</code> is returned.
   */
  public int getInt(String name, int defaultValue) {
    String valueString = get(name);
    if (valueString == null)
      return defaultValue;
    try {
      return Integer.parseInt(valueString);
    } catch (NumberFormatException e) {
      return defaultValue;
    }
  }

  /** Sets the value of the <code>name</code> property to an integer. */
  public void setInt(String name, int value) {
    set(name, Integer.toString(value));
  }


  /** Returns the value of the <code>name</code> property as a long.  If no
   * such property is specified, or if the specified value is not a valid
   * long, then <code>defaultValue</code> is returned.
   */
  public long getLong(String name, long defaultValue) {
    String valueString = get(name);
    if (valueString == null)
      return defaultValue;
    try {
      return Long.parseLong(valueString);
    } catch (NumberFormatException e) {
      return defaultValue;
    }
  }

  /** Sets the value of the <code>name</code> property to a long. */
  public void setLong(String name, long value) {
    set(name, Long.toString(value));
  }

  /** Returns the value of the <code>name</code> property as a float.  If no
   * such property is specified, or if the specified value is not a valid
   * float, then <code>defaultValue</code> is returned.
   */
  public float getFloat(String name, float defaultValue) {
    String valueString = get(name);
    if (valueString == null)
      return defaultValue;
    try {
      return Float.parseFloat(valueString);
    } catch (NumberFormatException e) {
      return defaultValue;
    }
  }

  /** Returns the value of the <code>name</code> property as an boolean.  If no
   * such property is specified, or if the specified value is not a valid
   * boolean, then <code>defaultValue</code> is returned.  Valid boolean values
   * are "true" and "false".
   */
  public boolean getBoolean(String name, boolean defaultValue) {
    String valueString = get(name);
    if ("true".equals(valueString))
      return true;
    else if ("false".equals(valueString))
      return false;
    else return defaultValue;
  }

  /** Sets the value of the <code>name</code> property to an integer. */
  public void setBoolean(String name, boolean value) {
    set(name, Boolean.toString(value));
  }

  /** Returns the value of the <code>name</code> property as an array of
   * strings.  If no such property is specified, then <code>null</code>
   * is returned.  Values are whitespace or comma delimted.
   */
  public String[] getStrings(String name) {
    String valueString = get(name);
    if (valueString == null)
      return null;
    StringTokenizer tokenizer = new StringTokenizer (valueString,", \t\n\r\f");
    List values = new ArrayList();
    while (tokenizer.hasMoreTokens()) {
      values.add(tokenizer.nextToken());
    }
    return (String[])values.toArray(new String[values.size()]);
  }

  /** Returns the value of the <code>name</code> property as a Class.  If no
   * such property is specified, then <code>defaultValue</code> is returned.
   */
  public Class getClass(String name, Class defaultValue) {
    String valueString = get(name);
    if (valueString == null)
      return defaultValue;
    try {
      return Class.forName(valueString);
    } catch (ClassNotFoundException e) {
      throw new RuntimeException(e);
    }
  }

  /** Returns the value of the <code>name</code> property as a Class.  If no
   * such property is specified, then <code>defaultValue</code> is returned.