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/*
 *
 *  *
 *  *  * Copyright 2015 Skymind,Inc.
 *  *  *
 *  *  *    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.canova.api.conf;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Serializable;
import java.io.Writer;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;

import org.canova.api.util.ReflectionUtils;
import org.canova.api.util.StringUtils;
import org.canova.api.writable.Writable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;
import org.xml.sax.SAXException;

/**
 * Provides access to configuration parameters.
 *
 * 
Resources

 *
 * 
Configurations are specified by resources. A resource contains a set of
 * name/value pairs as XML data. Each resource is named by either a 
 * String. If named by a String,
 * then the classpath is examined for a file with that name.  If named by a 
 * Path, then the local filesystem is examined directly, without 
 * referring to the classpath.
 *
 * 
Unless explicitly turned off, Hadoop by default specifies two 
 * resources, loaded in-order from the classpath: 
    
 * 
  1. core-default.xml
 * : Read-only defaults for hadoop.
    2. 
 * 
  2. core-site.xml: Site-specific configuration for a given hadoop
 * installation.
    3. 
 * 

 * Applications may add additional resources, which are loaded
 * subsequent to these resources in the order they are added.
 *
 * 
Final Parameters

 *
 * 
Configuration parameters may be declared final. 
 * Once a resource declares a value final, no subsequently-loaded 
 * resource can alter that value.  
 * For example, one might define a final parameter with:
 * 
 *  <property>
 *    <name>dfs.client.buffer.dir</name>
 *    <value>/tmp/hadoop/dfs/client</value>
 *    <final>true</final>
 *  </property>

 *
 * Administrators typically define parameters as final in 
 * core-site.xml for values that user applications may not alter.
 *
 * 
Variable Expansion

 *
 * 
Value strings are first processed for variable expansion. The
 * available properties are:
    
 * 
  1. Other properties defined in this Configuration; and, if a name is
 * undefined here,
    2. 
 * 
  2. Properties in {@link System#getProperties()}.
    3. 
 * 

 *
 * 
For example, if a configuration resource contains the following property
 * definitions: 
 * 
 *  <property>
 *    <name>basedir</name>
 *    <value>/user/${user.name}</value>
 *  </property>
 *
 *  <property>
 *    <name>tempdir</name>
 *    <value>${basedir}/tmp</value>
 *  </property>

 *
 * When conf.get("tempdir") is called, then ${basedir}
 * will be resolved to another property in this Configuration, while
 * ${user.name} would then ordinarily be resolved to the value
 * of the System property with that name.
 */
public class Configuration implements Iterable>,
        Writable, Serializable {
    private static final Logger LOG =
            LoggerFactory.getLogger(Configuration.class);

    private boolean quietmode = true;

    /**
     * List of configuration resources.
     */
    private ArrayList resources = new ArrayList<>();

    /**
     * List of configuration parameters marked final.
     */
    private Set finalParameters = new HashSet<>();

    private boolean loadDefaults = true;

    /**
     * Configuration objects
     */
    private static final WeakHashMap REGISTRY =
            new WeakHashMap<>();

    /**
     * List of default Resources. Resources are loaded in the order of the list
     * entries
     */
    private static final CopyOnWriteArrayList defaultResources =
            new CopyOnWriteArrayList<>();

    private static final ConcurrentMap>>
            CACHE_CLASSES = new ConcurrentHashMap<>();

    /**
     * Flag to indicate if the storage of resource which updates a key needs
     * to be stored for each key
     */
    private boolean storeResource;

    /**
     * Stores the mapping of key to the resource which modifies or loads
     * the key most recently
     */
    private HashMap updatingResource;

    static{
        //print deprecation warning if hadoop-site.xml is found in classpath
        ClassLoader cL = Thread.currentThread().getContextClassLoader();
        if (cL == null) {
            cL = Configuration.class.getClassLoader();
        }
        if(cL.getResource("hadoop-site.xml")!=null) {
            LOG.warn("DEPRECATED: hadoop-site.xml found in the classpath. " +
                    "Usage of hadoop-site.xml is deprecated. Instead use core-site.xml, "
                    + "mapred-site.xml and hdfs-site.xml to override properties of " +
                    "core-default.xml, mapred-default.xml and hdfs-default.xml " +
                    "respectively");
        }
        addDefaultResource("core-default.xml");
        addDefaultResource("core-site.xml");
    }

    private Properties properties;
    private Properties overlay;
    private transient ClassLoader classLoader;
    {
        classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            classLoader = Configuration.class.getClassLoader();
        }
    }




    /** A new configuration. */
    public Configuration() {
        this(true);
    }

    /** A new configuration where the behavior of reading from the default
     * resources can be turned off.
     *
     * If the parameter {@code loadDefaults} is false, the new instance
     * will not load resources from the default files.
     * @param loadDefaults specifies whether to load from the default files
     */
    public Configuration(boolean loadDefaults) {
        this.loadDefaults = loadDefaults;
        synchronized(Configuration.class) {
            REGISTRY.put(this, null);
        }
        this.storeResource = false;
    }

    /**
     * A new configuration with the same settings and additional facility for
     * storage of resource to each key which loads or updates
     * the key most recently
     * @param other the configuration from which to clone settings
     * @param storeResource flag to indicate if the storage of resource to
     * each key is to be stored
     */
    private Configuration(Configuration other, boolean storeResource) {
        this(other);
        this.loadDefaults = other.loadDefaults;
        this.storeResource = storeResource;
        if (storeResource) {
            updatingResource = new HashMap<>();
        }
    }

    /**
     * A new configuration with the same settings cloned from another.
     *
     * @param other the configuration from which to clone settings.
     */
    @SuppressWarnings("unchecked")
    public Configuration(Configuration other) {
        this.resources = (ArrayList)other.resources.clone();
        synchronized(other) {
            if (other.properties != null) {
                this.properties = (Properties)other.properties.clone();
            }

            if (other.overlay!=null) {
                this.overlay = (Properties)other.overlay.clone();
            }
        }

        this.finalParameters = new HashSet<>(other.finalParameters);
        synchronized(Configuration.class) {
            REGISTRY.put(this, null);
        }
    }

    /**
     * Add a default resource. Resources are loaded in the order of the resources
     * added.
     * @param name file name. File should be present in the classpath.
     */
    public static void addDefaultResource(String name) {
        // The lock hierarchy is that we must always lock
        // instances before locking the class. Since reloadConfiguration
        // is synchronized on the instance, we must not call conf.reloadConfiguration
        // while holding a lock on Configuration.class. Otherwise we could deadlock
        // if that conf is attempting to lock the Class
        ArrayList toReload;
        synchronized (Configuration.class) {
            if(defaultResources.contains(name)) {
                return;
            }
            defaultResources.add(name);
            // Make a copy so we don't iterate while not holding the lock
            toReload = new ArrayList<>(REGISTRY.size());
            toReload.addAll(REGISTRY.keySet());
        }
        for(Configuration conf : toReload) {
            if(conf.loadDefaults) {
                conf.reloadConfiguration();
            }
        }
    }

    /**
     * Add a configuration resource.
     *
     * The properties of this resource will override properties of previously
     * added resources, unless they were marked final.
     *
     * @param name resource to be added, the classpath is examined for a file
     *             with that name.
     */
    public void addResource(String name) {
        addResourceObject(name);
    }

    /**
     * Add a configuration resource.
     *
     * The properties of this resource will override properties of previously
     * added resources, unless they were marked final.
     *
     * @param url url of the resource to be added, the local filesystem is
     *            examined directly to find the resource, without referring to
     *            the classpath.
     */
    public void addResource(URL url) {
        addResourceObject(url);
    }


    /**
     * Add a configuration resource.
     *
     * The properties of this resource will override properties of previously
     * added resources, unless they were marked final.
     *
     * @param in InputStream to deserialize the object from.
     */
    public void addResource(InputStream in) {
        addResourceObject(in);
    }


    /**
     * Reload configuration from previously added resources.
     *
     * This method will clear all the configuration read from the added
     * resources, and final parameters. This will make the resources to
     * be read again before accessing the values. Values that are added
     * via set methods will overlay values read from the resources.
     */
    public synchronized void reloadConfiguration() {
        properties = null;                            // trigger reload
        finalParameters.clear();                      // clear site-limits
    }

    private synchronized void addResourceObject(Object resource) {
        resources.add(resource);                      // add to resources
        reloadConfiguration();
    }

    private static Pattern varPat = Pattern.compile("\\$\\{[^\\}\\$\u0020]+\\}");

  private String substituteVars(String expr) {
        if (expr == null) {
            return null;
        }
        Matcher match = varPat.matcher("");
        String eval = expr;
        int MAX_SUBST = 20;
        for(int s=0; s< MAX_SUBST; s++) {
            match.reset(eval);
            if (!match.find()) {
                return eval;
            }
            String var = match.group();
            var = var.substring(2, var.length()-1); // remove ${ .. }
            String val = null;
            try {
                val = System.getProperty(var);
            } catch(SecurityException se) {
                LOG.warn("Unexpected SecurityException in Configuration", se);
            }
            if (val == null) {
                val = getRaw(var);
            }
            if (val == null) {
                return eval; // return literal ${var}: var is unbound
            }
            // substitute
            eval = eval.substring(0, match.start())+val+eval.substring(match.end());
        }
        throw new IllegalStateException("Variable substitution depth too large: "
                + MAX_SUBST + " " + expr);
    }

    /**
     * Get the value of the name property, null if
     * no such property exists.
     *
     * Values are processed for variable expansion
     * before being returned.
     *
     * @param name the property name.
     * @return the value of the name property,
     *         or null if no such property exists.
     */
    public String get(String name) {
        return substituteVars(getProps().getProperty(name));
    }

    /**
     * Get the value of the name property, without doing
     * variable expansion.
     *
     * @param name the property name.
     * @return the value of the name property,
     *         or null if no such property exists.
     */
    public String getRaw(String name) {
        return getProps().getProperty(name);
    }

    /**
     * Set the value of the name property.
     *
     * @param name property name.
     * @param value property value.
     */
    public void set(String name, String value) {
        getOverlay().setProperty(name, value);
        getProps().setProperty(name, value);
    }

    /**
     * Sets a property if it is currently unset.
     * @param name the property name
     * @param value the new value
     */
    public void setIfUnset(String name, String value) {
        if (get(name) == null) {
            set(name, value);
        }
    }

    private synchronized Properties getOverlay() {
        if (overlay==null){
            overlay=new Properties();
        }
        return overlay;
    }

    /**
     * Get the value of the name property. If no such property
     * exists, then defaultValue is returned.
     *
     * @param name property name.
     * @param defaultValue default value.
     * @return property value, or defaultValue if the property
     *         doesn't exist.
     */
    public String get(String name, String defaultValue) {
        return substituteVars(getProps().getProperty(name, defaultValue));
    }

    /**
     * Get the value of the name property as an int.
     *
     * If no such property exists, or if the specified value is not a valid
     * int, then defaultValue is returned.
     *
     * @param name property name.
     * @param defaultValue default value.
     * @return property value as an int,
     *         or defaultValue.
     */
    public int getInt(String name, int defaultValue) {
        String valueString = get(name);
        if (valueString == null)
            return defaultValue;
        try {
            String hexString = getHexDigits(valueString);
            if (hexString != null) {
                return Integer.parseInt(hexString, 16);
            }
            return Integer.parseInt(valueString);
        } catch (NumberFormatException e) {
            return defaultValue;
        }
    }

    /**
     * Set the value of the name property to an int.
     *
     * @param name property name.
     * @param value int value of the property.
     */
    public void setInt(String name, int value) {
        set(name, Integer.toString(value));
    }


    /**
     * Get the value of the name property as a long.
     * If no such property is specified, or if the specified value is not a valid
     * long, then defaultValue is returned.
     *
     * @param name property name.
     * @param defaultValue default value.
     * @return property value as a long,
     *         or defaultValue.
     */
    public long getLong(String name, long defaultValue) {
        String valueString = get(name);
        if (valueString == null)
            return defaultValue;
        try {
            String hexString = getHexDigits(valueString);
            if (hexString != null) {
                return Long.parseLong(hexString, 16);
            }
            return Long.parseLong(valueString);
        } catch (NumberFormatException e) {
            return defaultValue;
        }
    }

    private String getHexDigits(String value) {
        boolean negative = false;
        String str = value;
        String hexString;
        if (value.startsWith("-")) {
            negative = true;
            str = value.substring(1);
        }
        if (str.startsWith("0x") || str.startsWith("0X")) {
            hexString = str.substring(2);
            if (negative) {
                hexString = "-" + hexString;
            }
            return hexString;
        }
        return null;
    }

    /**
     * Set the value of the name property to a long.
     *
     * @param name property name.
     * @param value long value of the property.
     */
    public void setLong(String name, long value) {
        set(name, Long.toString(value));
    }

    /**
     * Get the value of the name property as a float.
     * If no such property is specified, or if the specified value is not a valid
     * float, then defaultValue is returned.
     *
     * @param name property name.
     * @param defaultValue default value.
     * @return property value as a float,
     *         or defaultValue.
     */
    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;
        }
    }
    /**
     * Set the value of the name property to a float.
     *
     * @param name property name.
     * @param value property value.
     */
    public void setFloat(String name, float value) {
        set(name,Float.toString(value));
    }

    /**
     * Get the value of the name property as a boolean.
     * If no such property is specified, or if the specified value is not a valid
     * boolean, then defaultValue is returned.
     *
     * @param name property name.
     * @param defaultValue default value.
     * @return property value as a boolean,
     *         or defaultValue.
     */
    public boolean getBoolean(String name, boolean defaultValue) {
      String valueString = get(name);
      return "true".equals(valueString) ||
          !"false".equals(valueString) && defaultValue;
    }

    /**
     * Set the value of the name property to a boolean.
     *
     * @param name property name.
     * @param value boolean value of the property.
     */
    public void setBoolean(String name, boolean value) {
        set(name, Boolean.toString(value));
    }

    /**
     * Set the given property, if it is currently unset.
     * @param name property name
     * @param value new value
     */
    public void setBooleanIfUnset(String name, boolean value) {
        setIfUnset(name, Boolean.toString(value));
    }

    /**
     * Get the value of the name property as a Pattern.
     * If no such property is specified, or if the specified value is not a valid
     * Pattern, then DefaultValue is returned.
     *
     * @param name property name
     * @param defaultValue default value
     * @return property value as a compiled Pattern, or defaultValue
     */
    public Pattern getPattern(String name, Pattern defaultValue) {
        String valString = get(name);
        if (null == valString || "".equals(valString)) {
            return defaultValue;
        }
        try {
            return Pattern.compile(valString);
        } catch (PatternSyntaxException pse) {
            LOG.warn("Regular expression '" + valString + "' for property '" +
                    name + "' not valid. Using default", pse);
            return defaultValue;
        }
    }

    /**
     * Set the given property to Pattern.
     * If the pattern is passed as null, sets the empty pattern which results in
     * further calls to getPattern(...) returning the default value.
     *
     * @param name property name
     * @param pattern new value
     */
    public void setPattern(String name, Pattern pattern) {
        if (null == pattern) {
            set(name, null);
        } else {
            set(name, pattern.pattern());
        }
    }

    @Override
    public void write(DataOutput out) throws IOException {

    }

    @Override
    public void readFields(DataInput in) throws IOException {

    }

    /**
     * A class that represents a set of positive integer ranges. It parses
     * strings of the form: "2-3,5,7-" where ranges are separated by comma and
     * the lower/upper bounds are separated by dash. Either the lower or upper
     * bound may be omitted meaning all values up to or over. So the string
     * above means 2, 3, 5, and 7, 8, 9, ...
     */
    public static class IntegerRanges {
        private static class Range {
            int start;
            int end;
        }

        List ranges = new ArrayList();

        public IntegerRanges() {
        }

        public IntegerRanges(String newValue) {
            StringTokenizer itr = new StringTokenizer(newValue, ",");
            while (itr.hasMoreTokens()) {
                String rng = itr.nextToken().trim();
                String[] parts = rng.split("-", 3);
                if (parts.length < 1 || parts.length > 2) {
                    throw new IllegalArgumentException("integer range badly formed: " +
                            rng);
                }
                Range r = new Range();
                r.start = convertToInt(parts[0], 0);
                if (parts.length == 2) {
                    r.end = convertToInt(parts[1], Integer.MAX_VALUE);
                } else {
                    r.end = r.start;
                }
                if (r.start > r.end) {
                    throw new IllegalArgumentException("IntegerRange from " + r.start +
                            " to " + r.end + " is invalid");
                }
                ranges.add(r);
            }
        }

        /**
         * Convert a string to an int treating empty strings as the default value.
         * @param value the string value
         * @param defaultValue the value for if the string is empty
         * @return the desired integer
         */
        private static int convertToInt(String value, int defaultValue) {
            String trim = value.trim();
            if (trim.length() == 0) {
                return defaultValue;
            }
            return Integer.parseInt(trim);
        }

        /**
         * Is the given value in the set of ranges
         * @param value the value to check
         * @return is the value in the ranges?
         */
        public boolean isIncluded(int value) {
            for(Range r: ranges) {
                if (r.start <= value && value <= r.end) {
                    return true;
                }
            }
            return false;
        }

        @Override
        public String toString() {
            StringBuilder result = new StringBuilder();
            boolean first = true;
            for(Range r: ranges) {
                if (first) {
                    first = false;
                } else {
                    result.append(',');
                }
                result.append(r.start);
                result.append('-');
                result.append(r.end);
            }
            return result.toString();
        }
    }

    /**
     * Parse the given attribute as a set of integer ranges
     * @param name the attribute name
     * @param defaultValue the default value if it is not set
     * @return a new set of ranges from the configured value
     */
    public IntegerRanges getRange(String name, String defaultValue) {
        return new IntegerRanges(get(name, defaultValue));
    }

    /**
     * Get the comma delimited values of the name property as
     * a collection of Strings.
     * If no such property is specified then empty collection is returned.
     * 

     * This is an optimized version of {@link #getStrings(String)}
     *
     * @param name property name.
     * @return property value as a collection of Strings.
     */
    public Collection getStringCollection(String name) {
        String valueString = get(name);
        return StringUtils.getStringCollection(valueString);
    }

    /**
     * Get the comma delimited values of the name property as
     * an array of Strings.
     * If no such property is specified then null is returned.
     *
     * @param name property name.
     * @return property value as an array of Strings,
     *         or null.
     */
    public String[] getStrings(String name) {
        String valueString = get(name);
        return StringUtils.getStrings(valueString);
    }

    /**
     * Get the comma delimited values of the name property as
     * an array of Strings.
     * If no such property is specified then default value is returned.
     *
     * @param name property name.
     * @param defaultValue The default value
     * @return property value as an array of Strings,
     *         or default value.
     */
    public String[] getStrings(String name, String... defaultValue) {
        String valueString = get(name);
        if (valueString == null) {
            return defaultValue;
        } else {
            return StringUtils.getStrings(valueString);
        }
    }

    /**
     * Get the comma delimited values of the name property as
     * a collection of Strings, trimmed of the leading and trailing whitespace.
     * If no such property is specified then empty Collection is returned.
     *
     * @param name property name.
     * @return property value as a collection of Strings, or empty Collection
     */
    public Collection getTrimmedStringCollection(String name) {
        String valueString = get(name);
        if (null == valueString) {
          return Collections.emptyList();
        }
        return StringUtils.getTrimmedStringCollection(valueString);
    }

    /**
     * Get the comma delimited values of the name property as
     * an array of Strings, trimmed of the leading and trailing whitespace.
     * If no such property is specified then an empty array is returned.
     *
     * @param name property name.
     * @return property value as an array of trimmed Strings,
     *         or empty array.
     */
    public String[] getTrimmedStrings(String name) {
        String valueString = get(name);
        return StringUtils.getTrimmedStrings(valueString);
    }

    /**
     * Get the comma delimited values of the name property as
     * an array of Strings, trimmed of the leading and trailing whitespace.
     * If no such property is specified then default value is returned.
     *
     * @param name property name.
     * @param defaultValue The default value
     * @return property value as an array of trimmed Strings,
     *         or default value.
     */
    public String[] getTrimmedStrings(String name, String... defaultValue) {
        String valueString = get(name);
        if (null == valueString) {
            return defaultValue;
        } else {
            return StringUtils.getTrimmedStrings(valueString);
        }
    }

    /**
     * Set the array of string values for the name property as
     * as comma delimited values.
     *
     * @param name property name.
     * @param values The values
     */
    public void setStrings(String name, String... values) {
        set(name, StringUtils.arrayToString(values));
    }

    /**
     * Load a class by name.
     *
     * @param name the class name.
     * @return the class object.
     * @throws ClassNotFoundException if the class is not found.
     */
    public Class getClassByName(String name) throws ClassNotFoundException {
        Map> map = CACHE_CLASSES.get(classLoader);
        if (map == null) {
            Map> newMap = new ConcurrentHashMap<>();
            map = CACHE_CLASSES.putIfAbsent(classLoader, newMap);
            if (map == null) {
                map = newMap;
            }
        }

        Class clazz = map.get(name);
        if (clazz == null) {
            clazz = Class.forName(name, true, classLoader);
            if (clazz != null) {
                map.put(name, clazz);
            }
        }

        return clazz;
    }

    /**
     * Get the value of the name property
     * as an array of Class.
     * The value of the property specifies a list of comma separated class names.
     * If no such property is specified, then defaultValue is
     * returned.
     *
     * @param name the property name.
     * @param defaultValue default value.
     * @return property value as a Class[],
     *         or defaultValue.
     */
    public Class[] getClasses(String name, Class ... defaultValue) {
        String[] classnames = getStrings(name);
        if (classnames == null)
            return defaultValue;
        try {
            Class[] classes = new Class[classnames.length];
            for(int i = 0; i < classnames.length; i++) {
                classes[i] = getClassByName(classnames[i]);
            }
            return classes;
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Get the value of the name property as a Class.
     * If no such property is specified, then defaultValue is
     * returned.
     *
     * @param name the class name.
     * @param defaultValue default value.
     * @return property value as a Class,
     *         or defaultValue.
     */
    public Class getClass(String name, Class defaultValue) {
        String valueString = get(name);
        if (valueString == null)
            return defaultValue;
        try {
            return getClassByName(valueString);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Get the value of the name property as a Class
     * implementing the interface specified by xface.
     *
     * If no such property is specified, then defaultValue is
     * returned.
     *
     * An exception is thrown if the returned class does not implement the named
     * interface.
     *
     * @param name the class name.
     * @param defaultValue default value.
     * @param xface the interface implemented by the named class.
     * @return property value as a Class,
     *         or defaultValue.
     */
    public  Class getClass(String name,
                                           Class defaultValue,
                                           Class xface) {
        try {
            Class theClass = getClass(name, defaultValue);
            if (theClass != null && !xface.isAssignableFrom(theClass))
                throw new RuntimeException(theClass+" not "+xface.getName());
            else if (theClass != null)
                return theClass.asSubclass(xface);
            else
                return null;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Get the value of the name property as a List
     * of objects implementing the interface specified by xface.
     *
     * An exception is thrown if any of the classes does not exist, or if it does
     * not implement the named interface.
     *
     * @param name the property name.
     * @param xface the interface implemented by the classes named by
     *        name.
     * @return a List of objects implementing xface.
     */
    @SuppressWarnings("unchecked")
    public  List getInstances(String name, Class xface) {
        List ret = new ArrayList<>();
        Class[] classes = getClasses(name);
        for (Class cl: classes) {
            if (!xface.isAssignableFrom(cl)) {
                throw new RuntimeException(cl + " does not implement " + xface);
            }
            ret.add((U) ReflectionUtils.newInstance(cl, this));
        }
        return ret;
    }

    /**
     * Set the value of the name property to the name of a
     * theClass implementing the given interface xface.
     *
     * An exception is thrown if theClass does not implement the
     * interface xface.
     *
     * @param name property name.
     * @param theClass property value.
     * @param xface the interface implemented by the named class.
     */
    public void setClass(String name, Class theClass, Class xface) {
        if (!xface.isAssignableFrom(theClass))
            throw new RuntimeException(theClass+" not "+xface.getName());
        set(name, theClass.getName());
    }



    /**
     * Get a local file name under a directory named in dirsProp with
     * the given path.  If dirsProp contains multiple directories,
     * then one is chosen based on path's hash code.  If the selected
     * directory does not exist, an attempt is made to create it.
     *
     * @param dirsProp directory in which to locate the file.
     * @param path file-path.
     * @return local file under the directory with the given path.
     */
    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);
            File dir = file.getParentFile();
            if (dir.exists() || dir.mkdirs()) {
                return file;
            }
        }
        throw new IOException("No valid local directories in property: "+dirsProp);
    }

    /**
     * Get the {@link URL} for the named resource.
     *
     * @param name resource name.
     * @return the url for the named resource.
     */
    public URL getResource(String name) {
        return classLoader.getResource(name);
    }

    /**
     * Get an input stream attached to the configuration resource with the
     * given name.
     *
     * @param name configuration resource name.
     * @return an input stream attached to the resource.
     */
    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;
        }
    }

    /**
     * Get a {@link Reader} attached to the configuration resource with the
     * given name.
     *
     * @param name configuration resource name.
     * @return a reader attached to the resource.
     */
    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 = new Properties();
            loadResources(properties, resources, quietmode);
            if (overlay!= null) {
                properties.putAll(overlay);
                if (storeResource) {
                    for (Map.Entry item: overlay.entrySet()) {
                        updatingResource.put((String) item.getKey(), "Unknown");
                    }
                }
            }
        }
        return properties;
    }

    /**
     * Return the number of keys in the configuration.
     *
     * @return number of keys in the configuration.
     */
    public int size() {
        return getProps().size();
    }

    /**
     * Clears all keys from the configuration.
     */
    public void clear() {
        getProps().clear();
        getOverlay().clear();
    }

    /**
     * Get an {@link Iterator} to go through the list of String
     * key-value pairs in the configuration.
     *
     * @return an iterator over the entries.
     */
    public Iterator> iterator() {
        // Get a copy of just the string to string pairs. After the old object
        // methods that allow non-strings to be put into configurations are removed,
        // we could replace properties with a Map and get rid of this
        // code.
        Map result = new HashMap<>();
        for(Map.Entry item: getProps().entrySet()) {
            if (item.getKey() instanceof String &&
                    item.getValue() instanceof String) {
                result.put((String) item.getKey(), (String) item.getValue());
            }
        }
        return result.entrySet().iterator();
    }

    private void loadResources(Properties properties,
                               ArrayList resources,
                               boolean quiet) {
        if(loadDefaults) {
            // To avoid addResource causing a ConcurrentModificationException
            ArrayList toLoad;
            synchronized (Configuration.class) {
                toLoad = new ArrayList<>(defaultResources);
            }
            for (String resource : toLoad) {
                loadResource(properties, resource, quiet);
            }

            //support the hadoop-site.xml as a deprecated case
            if(getResource("hadoop-site.xml")!=null) {
                loadResource(properties, "hadoop-site.xml", quiet);
            }
        }

        for (Object resource : resources) {
            loadResource(properties, resource, quiet);
        }
    }

    private void loadResource(Properties properties, Object name, boolean quiet) {
        try {
            DocumentBuilderFactory docBuilderFactory
                    = DocumentBuilderFactory.newInstance();
            //ignore all comments inside the xml file
            docBuilderFactory.setIgnoringComments(true);

            //allow includes in the xml file
            docBuilderFactory.setNamespaceAware(true);
            try {
                docBuilderFactory.setXIncludeAware(true);
            } catch (UnsupportedOperationException e) {
                LOG.error("Failed to set setXIncludeAware(true) for parser "
                                + docBuilderFactory
                                + ":" + e,
                        e);
            }
            DocumentBuilder builder = docBuilderFactory.newDocumentBuilder();
            Document doc = null;
            Element root = null;

            if (name instanceof URL) {                  // an URL resource
                URL url = (URL)name;
                if (url != null) {
                    if (!quiet) {
                        LOG.info("parsing " + url);
                    }
                    doc = builder.parse(url.toString());
                }
            } else if (name instanceof String) {        // a CLASSPATH resource
                URL url = getResource((String)name);
                if (url != null) {
                    if (!quiet) {
                        LOG.info("parsing " + url);
                    }
                    doc = builder.parse(url.toString());
                }
            }  else if (name instanceof InputStream) {
                try {
                    doc = builder.parse((InputStream)name);
                } finally {
                    ((InputStream)name).close();
                }
            } else if (name instanceof Element) {
                root = (Element)name;
            }

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

            if (root == null) {
                root = doc.getDocumentElement();
            }
            if (!"configuration".equals(root.getTagName()))
                LOG.error("bad conf file: top-level element not ");
            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 ("configuration".equals(prop.getTagName())) {
                    loadResource(properties, prop, quiet);
                    continue;
                }
                if (!"property".equals(prop.getTagName()))
                    LOG.warn("bad conf file: element not ");
                NodeList fields = prop.getChildNodes();
                String attr = null;
                String value = null;
                boolean finalParameter = false;
                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()) && field.hasChildNodes())
                        attr = ((Text)field.getFirstChild()).getData().trim();
                    if ("value".equals(field.getTagName()) && field.hasChildNodes())
                        value = ((Text)field.getFirstChild()).getData();
                    if ("final".equals(field.getTagName()) && field.hasChildNodes())
                        finalParameter = "true".equals(((Text)field.getFirstChild()).getData());
                }

                // Ignore this parameter if it has already been marked as 'final'
                if (attr != null && value != null) {
                    if (!finalParameters.contains(attr)) {
                        properties.setProperty(attr, value);
                        if (storeResource) {
                            updatingResource.put(attr, name.toString());
                        }
                        if (finalParameter)
                            finalParameters.add(attr);
                    } else {
                        LOG.warn(name+":a attempt to override final parameter: "+attr
                                +";  Ignoring.");
                    }
                }
            }

        } catch (IOException | ParserConfigurationException | SAXException | DOMException e) {
            LOG.error("error parsing conf file: " + e);
            throw new RuntimeException(e);
        }
    }

    /**
     * Write out the non-default properties in this configuration to the give
     * {@link OutputStream}.
     *
     * @param out the output stream to write to.
     */
    public void writeXml(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;
                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);
        }
    }

    /**
     *  Writes out all the parameters and their properties (final and resource) to
     *  the given {@link Writer}
     *  The format of the output would be
     *  { "properties" : [ {key1,value1,key1.isFinal,key1.resource}, {key2,value2,
     *  key2.isFinal,key2.resource}... ] }
     *  It does not output the parameters of the configuration object which is
     *  loaded from an input stream.
     * @param out the Writer to write to
     * @throws IOException
     */
    public static void dumpConfiguration(Configuration conf,
                                         Writer out) throws IOException {
        Configuration config = new Configuration(conf,true);
        config.reloadConfiguration();
        JsonFactory dumpFactory = new JsonFactory();
        JsonGenerator dumpGenerator = dumpFactory.createGenerator(out);
        dumpGenerator.writeStartObject();
        dumpGenerator.writeFieldName("properties");
        dumpGenerator.writeStartArray();
        dumpGenerator.flush();
        for (Map.Entry item: config.getProps().entrySet()) {
            dumpGenerator.writeStartObject();
            dumpGenerator.writeStringField("key", (String) item.getKey());
            dumpGenerator.writeStringField("value",
                    config.get((String) item.getKey()));
            dumpGenerator.writeBooleanField("isFinal",
                    config.finalParameters.contains(item.getKey()));
            dumpGenerator.writeStringField("resource",
                    config.updatingResource.get(item.getKey()));
            dumpGenerator.writeEndObject();
        }
        dumpGenerator.writeEndArray();
        dumpGenerator.writeEndObject();
        dumpGenerator.flush();
    }

    /**
     * Get the {@link ClassLoader} for this job.
     *
     * @return the correct class loader.
     */
    public ClassLoader getClassLoader() {
        return classLoader;
    }

    /**
     * Set the class loader that will be used to load the various objects.
     *
     * @param classLoader the new class loader.
     */
    public void setClassLoader(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Configuration: ");
        if(loadDefaults) {
            synchronized (Configuration.class) {
                toString(defaultResources, sb);
            }
            if(resources.size()>0) {
                sb.append(", ");
            }
        }
        toString(resources, sb);
        return sb.toString();
    }

    private void toString(List resources, StringBuilder sb) {
        ListIterator i = resources.listIterator();
        while (i.hasNext()) {
            if (i.nextIndex() != 0) {
                sb.append(", ");
            }
            sb.append(i.next());
        }
    }

    /**
     * Set the quietness-mode.
     *
     * In the quiet-mode, error and informational messages might not be logged.
     *
     * @param quietmode true to set quiet-mode on, false
     *              to turn it off.
     */
    public synchronized void setQuietMode(boolean quietmode) {
        this.quietmode = quietmode;
    }

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


}    

    

    

            

    

            



    
    






    
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