src/main/java/org/apache/log4j/helpers/OptionConverter.java - logging-log4j1 - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You 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.log4j.helpers;

 import java.io.InputStream;
 import java.io.InterruptedIOException;
 import java.net.URL;
 import java.util.Properties;

 import org.apache.log4j.Level;
 import org.apache.log4j.PropertyConfigurator;
 import org.apache.log4j.spi.Configurator;
 import org.apache.log4j.spi.LoggerRepository;

 // Contributors:   Avy Sharell (sharell@online.fr)
 //                 Matthieu Verbert (mve@zurich.ibm.com)
 //                 Colin Sampaleanu

 /**
    A convenience class to convert property values to specific types.

    @author Ceki G&uuml;lc&uuml;
    @author Simon Kitching;
    @author Anders Kristensen
 */
 public class OptionConverter {

   static String DELIM_START = "${";
   static char   DELIM_STOP  = '}';
   static int DELIM_START_LEN = 2;
   static int DELIM_STOP_LEN  = 1;

   /** OptionConverter is a static class. */
   private OptionConverter() {}

   public
   static
   String[] concatanateArrays(String[] l, String[] r) {
     int len = l.length + r.length;
     String[] a = new String[len];

     System.arraycopy(l, 0, a, 0, l.length);
     System.arraycopy(r, 0, a, l.length, r.length);

     return a;
   }

   public
   static
   String convertSpecialChars(String s) {
     char c;
     int len = s.length();
     StringBuffer sbuf = new StringBuffer(len);

     int i = 0;
     while(i < len) {
       c = s.charAt(i++);
       if (c == '\\') {
 	c =  s.charAt(i++);
 	if(c == 'n')      c = '\n';
 	else if(c == 'r') c = '\r';
 	else if(c == 't') c = '\t';
 	else if(c == 'f') c = '\f';
 	else if(c == '\b') c = '\b';
 	else if(c == '\"') c = '\"';
 	else if(c == '\'') c = '\'';
 	else if(c == '\\') c = '\\';
       }
       sbuf.append(c);
     }
     return sbuf.toString();
   }


   /**
      Very similar to <code>System.getProperty</code> except
      that the {@link SecurityException} is hidden.

      @param key The key to search for.
      @param def The default value to return.
      @return the string value of the system property, or the default
      value if there is no property with that key.

      @since 1.1 */
   public
   static
   String getSystemProperty(String key, String def) {
     try {
       return System.getProperty(key, def);
     } catch(Throwable e) { // MS-Java throws com.ms.security.SecurityExceptionEx
       LogLog.debug("Was not allowed to read system property \""+key+"\".");
       return def;
     }
   }


   public
   static
   Object instantiateByKey(Properties props, String key, Class superClass,
 				Object defaultValue) {

     // Get the value of the property in string form
     String className = findAndSubst(key, props);
     if(className == null) {
       LogLog.error("Could not find value for key " + key);
       return defaultValue;
     }
     // Trim className to avoid trailing spaces that cause problems.
     return OptionConverter.instantiateByClassName(className.trim(), superClass,
 						  defaultValue);
   }

   /**
      If <code>value</code> is "true", then <code>true</code> is
      returned. If <code>value</code> is "false", then
      <code>true</code> is returned. Otherwise, <code>default</code> is
      returned.

      <p>Case of value is unimportant.  */
   public
   static
   boolean toBoolean(String value, boolean dEfault) {
     if(value == null)
       return dEfault;
     String trimmedVal = value.trim();
     if("true".equalsIgnoreCase(trimmedVal))
       return true;
     if("false".equalsIgnoreCase(trimmedVal))
       return false;
     return dEfault;
   }

   public
   static
   int toInt(String value, int dEfault) {
     if(value != null) {
       String s = value.trim();
       try {
 	return Integer.valueOf(s).intValue();
       }
       catch (NumberFormatException e) {
 	 LogLog.error("[" + s + "] is not in proper int form.");
 	e.printStackTrace();
       }
     }
     return dEfault;
   }

   /**
      Converts a standard or custom priority level to a Level
      object.  <p> If <code>value</code> is of form
      "level#classname", then the specified class' toLevel method
      is called to process the specified level string; if no '#'
      character is present, then the default {@link org.apache.log4j.Level}
      class is used to process the level value.

      <p>As a special case, if the <code>value</code> parameter is
      equal to the string "NULL", then the value <code>null</code> will
      be returned.

      <p> If any error occurs while converting the value to a level,
      the <code>defaultValue</code> parameter, which may be
      <code>null</code>, is returned.

      <p> Case of <code>value</code> is insignificant for the level level, but is
      significant for the class name part, if present.

      @since 1.1 */
   public
   static
   Level toLevel(String value, Level defaultValue) {
     if(value == null)
       return defaultValue;

     value = value.trim();

     int hashIndex = value.indexOf('#');
     if (hashIndex == -1) {
       if("NULL".equalsIgnoreCase(value)) {
 	return null;
       } else {
 	// no class name specified : use standard Level class
 	return(Level) Level.toLevel(value, defaultValue);
       }
     }

     Level result = defaultValue;

     String clazz = value.substring(hashIndex+1);
     String levelName = value.substring(0, hashIndex);

     // This is degenerate case but you never know.
     if("NULL".equalsIgnoreCase(levelName)) {
 	return null;
     }

     LogLog.debug("toLevel" + ":class=[" + clazz + "]"
 		 + ":pri=[" + levelName + "]");

     try {
       Class customLevel = Loader.loadClass(clazz);

       // get a ref to the specified class' static method
       // toLevel(String, org.apache.log4j.Level)
       Class[] paramTypes = new Class[] { String.class,
 					 org.apache.log4j.Level.class
                                        };
       java.lang.reflect.Method toLevelMethod =
                       customLevel.getMethod("toLevel", paramTypes);

       // now call the toLevel method, passing level string + default
       Object[] params = new Object[] {levelName, defaultValue};
       Object o = toLevelMethod.invoke(null, params);

       result = (Level) o;
     } catch(ClassNotFoundException e) {
       LogLog.warn("custom level class [" + clazz + "] not found.");
     } catch(NoSuchMethodException e) {
       LogLog.warn("custom level class [" + clazz + "]"
         + " does not have a class function toLevel(String, Level)", e);
     } catch(java.lang.reflect.InvocationTargetException e) {
         if (e.getTargetException() instanceof InterruptedException
                 || e.getTargetException() instanceof InterruptedIOException) {
             Thread.currentThread().interrupt();
         }
       LogLog.warn("custom level class [" + clazz + "]"
 		   + " could not be instantiated", e);
     } catch(ClassCastException e) {
       LogLog.warn("class [" + clazz
         + "] is not a subclass of org.apache.log4j.Level", e);
     } catch(IllegalAccessException e) {
       LogLog.warn("class ["+clazz+
 		   "] cannot be instantiated due to access restrictions", e);
     } catch(RuntimeException e) {
       LogLog.warn("class ["+clazz+"], level ["+levelName+
 		   "] conversion failed.", e);
     }
     return result;
    }

   public
   static
   long toFileSize(String value, long dEfault) {
     if(value == null)
       return dEfault;

     String s = value.trim().toUpperCase();
     long multiplier = 1;
     int index;

     if((index = s.indexOf("KB")) != -1) {
       multiplier = 1024;
       s = s.substring(0, index);
     }
     else if((index = s.indexOf("MB")) != -1) {
       multiplier = 1024*1024;
       s = s.substring(0, index);
     }
     else if((index = s.indexOf("GB")) != -1) {
       multiplier = 1024*1024*1024;
       s = s.substring(0, index);
     }
     if(s != null) {
       try {
 	return Long.valueOf(s).longValue() * multiplier;
       }
       catch (NumberFormatException e) {
 	LogLog.error("[" + s + "] is not in proper int form.");
 	LogLog.error("[" + value + "] not in expected format.", e);
       }
     }
     return dEfault;
   }

   /**
      Find the value corresponding to <code>key</code> in
      <code>props</code>. Then perform variable substitution on the
      found value.

  */
   public
   static
   String findAndSubst(String key, Properties props) {
     String value = props.getProperty(key);
     if(value == null)
       return null;

     try {
       return substVars(value, props);
     } catch(IllegalArgumentException e) {
       LogLog.error("Bad option value ["+value+"].", e);
       return value;
     }
   }

   /**
      Instantiate an object given a class name. Check that the
      <code>className</code> is a subclass of
      <code>superClass</code>. If that test fails or the object could
      not be instantiated, then <code>defaultValue</code> is returned.

      @param className The fully qualified class name of the object to instantiate.
      @param superClass The class to which the new object should belong.
      @param defaultValue The object to return in case of non-fulfillment
    */
   public
   static
   Object instantiateByClassName(String className, Class superClass,
 				Object defaultValue) {
     if(className != null) {
       try {
 	Class classObj = Loader.loadClass(className);
 	if(!superClass.isAssignableFrom(classObj)) {
 	  LogLog.error("A \""+className+"\" object is not assignable to a \""+
 		       superClass.getName() + "\" variable.");
 	  LogLog.error("The class \""+ superClass.getName()+"\" was loaded by ");
 	  LogLog.error("["+superClass.getClassLoader()+"] whereas object of type ");
 	  LogLog.error("\"" +classObj.getName()+"\" was loaded by ["
 		       +classObj.getClassLoader()+"].");
 	  return defaultValue;
 	}
 	return classObj.newInstance();
       } catch (ClassNotFoundException e) {
 	    LogLog.error("Could not instantiate class [" + className + "].", e);
       } catch (IllegalAccessException e) {
 	    LogLog.error("Could not instantiate class [" + className + "].", e);
       } catch (InstantiationException e) {
         LogLog.error("Could not instantiate class [" + className + "].", e);
       } catch (RuntimeException e) {
 	    LogLog.error("Could not instantiate class [" + className + "].", e);
       }
     }
     return defaultValue;
   }


   /**
      Perform variable substitution in string <code>val</code> from the
      values of keys found in the system propeties.

      <p>The variable substitution delimeters are <b>${</b> and <b>}</b>.

      <p>For example, if the System properties contains "key=value", then
      the call
      <pre>
      String s = OptionConverter.substituteVars("Value of key is ${key}.");
      </pre>

      will set the variable <code>s</code> to "Value of key is value.".

      <p>If no value could be found for the specified key, then the
      <code>props</code> parameter is searched, if the value could not
      be found there, then substitution defaults to the empty string.

      <p>For example, if system propeties contains no value for the key
      "inexistentKey", then the call

      <pre>
      String s = OptionConverter.subsVars("Value of inexistentKey is [${inexistentKey}]");
      </pre>
      will set <code>s</code> to "Value of inexistentKey is []"

      <p>An {@link java.lang.IllegalArgumentException} is thrown if
      <code>val</code> contains a start delimeter "${" which is not
      balanced by a stop delimeter "}". </p>

      <p><b>Author</b> Avy Sharell</a></p>

      @param val The string on which variable substitution is performed.
      @throws IllegalArgumentException if <code>val</code> is malformed.

   */
   public static
   String substVars(String val, Properties props) throws
                         IllegalArgumentException {

     StringBuffer sbuf = new StringBuffer();

     int i = 0;
     int j, k;

     while(true) {
       j=val.indexOf(DELIM_START, i);
       if(j == -1) {
 	// no more variables
 	if(i==0) { // this is a simple string
 	  return val;
 	} else { // add the tail string which contails no variables and return the result.
 	  sbuf.append(val.substring(i, val.length()));
 	  return sbuf.toString();
 	}
       } else {
 	sbuf.append(val.substring(i, j));
 	k = val.indexOf(DELIM_STOP, j);
 	if(k == -1) {
 	  throw new IllegalArgumentException('"'+val+
 		      "\" has no closing brace. Opening brace at position " + j
 					     + '.');
 	} else {
 	  j += DELIM_START_LEN;
 	  String key = val.substring(j, k);
 	  // first try in System properties
 	  String replacement = getSystemProperty(key, null);
 	  // then try props parameter
 	  if(replacement == null && props != null) {
 	    replacement =  props.getProperty(key);
 	  }

 	  if(replacement != null) {
 	    // Do variable substitution on the replacement string
 	    // such that we can solve "Hello ${x2}" as "Hello p1"
             // the where the properties are
 	    // x1=p1
             // x2=${x1}
 	    String recursiveReplacement = substVars(replacement, props);
 	    sbuf.append(recursiveReplacement);
 	  }
 	  i = k + DELIM_STOP_LEN;
 	}
       }
     }
   }

     /**
      * Configure log4j given an {@link InputStream}.
      *
      * <p>
      * The InputStream will be interpreted by a new instance of a log4j configurator.
      * </p>
      * <p>
      * All configurations steps are taken on the <code>hierarchy</code> passed as a parameter.
      * </p>
      *
      * @param inputStream
      *            The configuration input stream.
      * @param clazz
      *            The class name, of the log4j configurator which will parse the <code>inputStream</code>. This must be a
      *            subclass of {@link Configurator}, or null. If this value is null then a default configurator of
      *            {@link PropertyConfigurator} is used.
      * @param hierarchy
      *            The {@link org.apache.log4j.Hierarchy} to act on.
      * @since 1.2.17
      */

 static
 public
 void selectAndConfigure(InputStream inputStream, String clazz, LoggerRepository hierarchy) {
 Configurator configurator = null;

 if(clazz != null) {
   LogLog.debug("Preferred configurator class: " + clazz);
   configurator = (Configurator) instantiateByClassName(clazz,
                            Configurator.class,
                            null);
   if(configurator == null) {
    LogLog.error("Could not instantiate configurator ["+clazz+"].");
    return;
   }
 } else {
   configurator = new PropertyConfigurator();
 }

 configurator.doConfigure(inputStream, hierarchy);
 }


   /**
      Configure log4j given a URL.

      <p>The url must point to a file or resource which will be interpreted by
      a new instance of a log4j configurator.

      <p>All configurations steps are taken on the
      <code>hierarchy</code> passed as a parameter.

      <p>
      @param url The location of the configuration file or resource.
      @param clazz The classname, of the log4j configurator which will parse
      the file or resource at <code>url</code>. This must be a subclass of
      {@link Configurator}, or null. If this value is null then a default
      configurator of {@link PropertyConfigurator} is used, unless the
      filename pointed to by <code>url</code> ends in '.xml', in which case
      {@link org.apache.log4j.xml.DOMConfigurator} is used.
      @param hierarchy The {@link org.apache.log4j.Hierarchy} to act on.

      @since 1.1.4 */

   static
   public
   void selectAndConfigure(URL url, String clazz, LoggerRepository hierarchy) {
    Configurator configurator = null;
    String filename = url.getFile();

    if(clazz == null && filename != null && filename.endsWith(".xml")) {
      clazz = "org.apache.log4j.xml.DOMConfigurator";
    }

    if(clazz != null) {
      LogLog.debug("Preferred configurator class: " + clazz);
      configurator = (Configurator) instantiateByClassName(clazz,
 							  Configurator.class,
 							  null);
      if(configurator == null) {
    	  LogLog.error("Could not instantiate configurator ["+clazz+"].");
    	  return;
      }
    } else {
      configurator = new PropertyConfigurator();
    }

    configurator.doConfigure(url, hierarchy);
   }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You 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.log4j.helpers;

	import java.io.InputStream;
	import java.io.InterruptedIOException;
	import java.net.URL;
	import java.util.Properties;

	import org.apache.log4j.Level;
	import org.apache.log4j.PropertyConfigurator;
	import org.apache.log4j.spi.Configurator;
	import org.apache.log4j.spi.LoggerRepository;

	// Contributors: Avy Sharell (sharell@online.fr)
	// Matthieu Verbert (mve@zurich.ibm.com)
	// Colin Sampaleanu

	/**
	A convenience class to convert property values to specific types.

	@author Ceki Gülcü
	@author Simon Kitching;
	@author Anders Kristensen
	*/
	public class OptionConverter {

	static String DELIM_START = "${";
	static char DELIM_STOP = '}';
	static int DELIM_START_LEN = 2;
	static int DELIM_STOP_LEN = 1;

	/** OptionConverter is a static class. */
	private OptionConverter() {}

	public
	static
	String[] concatanateArrays(String[] l, String[] r) {
	int len = l.length + r.length;
	String[] a = new String[len];

	System.arraycopy(l, 0, a, 0, l.length);
	System.arraycopy(r, 0, a, l.length, r.length);

	return a;
	}

	public
	static
	String convertSpecialChars(String s) {
	char c;
	int len = s.length();
	StringBuffer sbuf = new StringBuffer(len);

	int i = 0;
	while(i < len) {
	c = s.charAt(i++);
	if (c == '\\') {
	c = s.charAt(i++);
	if(c == 'n') c = '\n';
	else if(c == 'r') c = '\r';
	else if(c == 't') c = '\t';
	else if(c == 'f') c = '\f';
	else if(c == '\b') c = '\b';
	else if(c == '\"') c = '\"';
	else if(c == '\'') c = '\'';
	else if(c == '\\') c = '\\';
	}
	sbuf.append(c);
	}
	return sbuf.toString();
	}


	/**
	Very similar to <code>System.getProperty</code> except
	that the {@link SecurityException} is hidden.

	@param key The key to search for.
	@param def The default value to return.
	@return the string value of the system property, or the default
	value if there is no property with that key.

	@since 1.1 */
	public
	static
	String getSystemProperty(String key, String def) {
	try {
	return System.getProperty(key, def);
	} catch(Throwable e) { // MS-Java throws com.ms.security.SecurityExceptionEx
	LogLog.debug("Was not allowed to read system property \""+key+"\".");
	return def;
	}
	}


	public
	static
	Object instantiateByKey(Properties props, String key, Class superClass,
	Object defaultValue) {

	// Get the value of the property in string form
	String className = findAndSubst(key, props);
	if(className == null) {
	LogLog.error("Could not find value for key " + key);
	return defaultValue;
	}
	// Trim className to avoid trailing spaces that cause problems.
	return OptionConverter.instantiateByClassName(className.trim(), superClass,
	defaultValue);
	}

	/**
	If <code>value</code> is "true", then <code>true</code> is
	returned. If <code>value</code> is "false", then
	<code>true</code> is returned. Otherwise, <code>default</code> is
	returned.

	<p>Case of value is unimportant. */
	public
	static
	boolean toBoolean(String value, boolean dEfault) {
	if(value == null)
	return dEfault;
	String trimmedVal = value.trim();
	if("true".equalsIgnoreCase(trimmedVal))
	return true;
	if("false".equalsIgnoreCase(trimmedVal))
	return false;
	return dEfault;
	}

	public
	static
	int toInt(String value, int dEfault) {
	if(value != null) {
	String s = value.trim();
	try {
	return Integer.valueOf(s).intValue();
	}
	catch (NumberFormatException e) {
	LogLog.error("[" + s + "] is not in proper int form.");
	e.printStackTrace();
	}
	}
	return dEfault;
	}

	/**
	Converts a standard or custom priority level to a Level
	object. <p> If <code>value</code> is of form
	"level#classname", then the specified class' toLevel method
	is called to process the specified level string; if no '#'
	character is present, then the default {@link org.apache.log4j.Level}
	class is used to process the level value.

	<p>As a special case, if the <code>value</code> parameter is
	equal to the string "NULL", then the value <code>null</code> will
	be returned.

	<p> If any error occurs while converting the value to a level,
	the <code>defaultValue</code> parameter, which may be
	<code>null</code>, is returned.

	<p> Case of <code>value</code> is insignificant for the level level, but is
	significant for the class name part, if present.

	@since 1.1 */
	public
	static
	Level toLevel(String value, Level defaultValue) {
	if(value == null)
	return defaultValue;

	value = value.trim();

	int hashIndex = value.indexOf('#');
	if (hashIndex == -1) {
	if("NULL".equalsIgnoreCase(value)) {
	return null;
	} else {
	// no class name specified : use standard Level class
	return(Level) Level.toLevel(value, defaultValue);
	}
	}

	Level result = defaultValue;

	String clazz = value.substring(hashIndex+1);
	String levelName = value.substring(0, hashIndex);

	// This is degenerate case but you never know.
	if("NULL".equalsIgnoreCase(levelName)) {
	return null;
	}

	LogLog.debug("toLevel" + ":class=[" + clazz + "]"
	+ ":pri=[" + levelName + "]");

	try {
	Class customLevel = Loader.loadClass(clazz);

	// get a ref to the specified class' static method
	// toLevel(String, org.apache.log4j.Level)
	Class[] paramTypes = new Class[] { String.class,
	org.apache.log4j.Level.class
	};
	java.lang.reflect.Method toLevelMethod =
	customLevel.getMethod("toLevel", paramTypes);

	// now call the toLevel method, passing level string + default
	Object[] params = new Object[] {levelName, defaultValue};
	Object o = toLevelMethod.invoke(null, params);

	result = (Level) o;
	} catch(ClassNotFoundException e) {
	LogLog.warn("custom level class [" + clazz + "] not found.");
	} catch(NoSuchMethodException e) {
	LogLog.warn("custom level class [" + clazz + "]"
	+ " does not have a class function toLevel(String, Level)", e);
	} catch(java.lang.reflect.InvocationTargetException e) {
	if (e.getTargetException() instanceof InterruptedException
	\|\| e.getTargetException() instanceof InterruptedIOException) {
	Thread.currentThread().interrupt();
	}
	LogLog.warn("custom level class [" + clazz + "]"
	+ " could not be instantiated", e);
	} catch(ClassCastException e) {
	LogLog.warn("class [" + clazz
	+ "] is not a subclass of org.apache.log4j.Level", e);
	} catch(IllegalAccessException e) {
	LogLog.warn("class ["+clazz+
	"] cannot be instantiated due to access restrictions", e);
	} catch(RuntimeException e) {
	LogLog.warn("class ["+clazz+"], level ["+levelName+
	"] conversion failed.", e);
	}
	return result;
	}

	public
	static
	long toFileSize(String value, long dEfault) {
	if(value == null)
	return dEfault;

	String s = value.trim().toUpperCase();
	long multiplier = 1;
	int index;

	if((index = s.indexOf("KB")) != -1) {
	multiplier = 1024;
	s = s.substring(0, index);
	}
	else if((index = s.indexOf("MB")) != -1) {
	multiplier = 1024*1024;
	s = s.substring(0, index);
	}
	else if((index = s.indexOf("GB")) != -1) {
	multiplier = 102410241024;
	s = s.substring(0, index);
	}
	if(s != null) {
	try {
	return Long.valueOf(s).longValue() * multiplier;
	}
	catch (NumberFormatException e) {
	LogLog.error("[" + s + "] is not in proper int form.");
	LogLog.error("[" + value + "] not in expected format.", e);
	}
	}
	return dEfault;
	}

	/**
	Find the value corresponding to <code>key</code> in
	<code>props</code>. Then perform variable substitution on the
	found value.

	*/
	public
	static
	String findAndSubst(String key, Properties props) {
	String value = props.getProperty(key);
	if(value == null)
	return null;

	try {
	return substVars(value, props);
	} catch(IllegalArgumentException e) {
	LogLog.error("Bad option value ["+value+"].", e);
	return value;
	}
	}

	/**
	Instantiate an object given a class name. Check that the
	<code>className</code> is a subclass of
	<code>superClass</code>. If that test fails or the object could
	not be instantiated, then <code>defaultValue</code> is returned.

	@param className The fully qualified class name of the object to instantiate.
	@param superClass The class to which the new object should belong.
	@param defaultValue The object to return in case of non-fulfillment
	*/
	public
	static
	Object instantiateByClassName(String className, Class superClass,
	Object defaultValue) {
	if(className != null) {
	try {
	Class classObj = Loader.loadClass(className);
	if(!superClass.isAssignableFrom(classObj)) {
	LogLog.error("A \""+className+"\" object is not assignable to a \""+
	superClass.getName() + "\" variable.");
	LogLog.error("The class \""+ superClass.getName()+"\" was loaded by ");
	LogLog.error("["+superClass.getClassLoader()+"] whereas object of type ");
	LogLog.error("\"" +classObj.getName()+"\" was loaded by ["
	+classObj.getClassLoader()+"].");
	return defaultValue;
	}
	return classObj.newInstance();
	} catch (ClassNotFoundException e) {
	LogLog.error("Could not instantiate class [" + className + "].", e);
	} catch (IllegalAccessException e) {
	LogLog.error("Could not instantiate class [" + className + "].", e);
	} catch (InstantiationException e) {
	LogLog.error("Could not instantiate class [" + className + "].", e);
	} catch (RuntimeException e) {
	LogLog.error("Could not instantiate class [" + className + "].", e);
	}
	}
	return defaultValue;
	}


	/**
	Perform variable substitution in string <code>val</code> from the
	values of keys found in the system propeties.

	<p>The variable substitution delimeters are <b>${</b> and <b>}</b>.

	<p>For example, if the System properties contains "key=value", then
	the call
	<pre>
	String s = OptionConverter.substituteVars("Value of key is ${key}.");
	</pre>

	will set the variable <code>s</code> to "Value of key is value.".

	<p>If no value could be found for the specified key, then the
	<code>props</code> parameter is searched, if the value could not
	be found there, then substitution defaults to the empty string.

	<p>For example, if system propeties contains no value for the key
	"inexistentKey", then the call

	<pre>
	String s = OptionConverter.subsVars("Value of inexistentKey is [${inexistentKey}]");
	</pre>
	will set <code>s</code> to "Value of inexistentKey is []"

	<p>An {@link java.lang.IllegalArgumentException} is thrown if
	<code>val</code> contains a start delimeter "${" which is not
	balanced by a stop delimeter "}". </p>

	<p><b>Author</b> Avy Sharell</a></p>

	@param val The string on which variable substitution is performed.
	@throws IllegalArgumentException if <code>val</code> is malformed.

	*/
	public static
	String substVars(String val, Properties props) throws
	IllegalArgumentException {

	StringBuffer sbuf = new StringBuffer();

	int i = 0;
	int j, k;

	while(true) {
	j=val.indexOf(DELIM_START, i);
	if(j == -1) {
	// no more variables
	if(i==0) { // this is a simple string
	return val;
	} else { // add the tail string which contails no variables and return the result.
	sbuf.append(val.substring(i, val.length()));
	return sbuf.toString();
	}
	} else {
	sbuf.append(val.substring(i, j));
	k = val.indexOf(DELIM_STOP, j);
	if(k == -1) {
	throw new IllegalArgumentException('"'+val+
	"\" has no closing brace. Opening brace at position " + j
	+ '.');
	} else {
	j += DELIM_START_LEN;
	String key = val.substring(j, k);
	// first try in System properties
	String replacement = getSystemProperty(key, null);
	// then try props parameter
	if(replacement == null && props != null) {
	replacement = props.getProperty(key);
	}

	if(replacement != null) {
	// Do variable substitution on the replacement string
	// such that we can solve "Hello ${x2}" as "Hello p1"
	// the where the properties are
	// x1=p1
	// x2=${x1}
	String recursiveReplacement = substVars(replacement, props);
	sbuf.append(recursiveReplacement);
	}
	i = k + DELIM_STOP_LEN;
	}
	}
	}
	}

	/**
	* Configure log4j given an {@link InputStream}.
	*
	* <p>
	* The InputStream will be interpreted by a new instance of a log4j configurator.
	* </p>
	* <p>
	* All configurations steps are taken on the <code>hierarchy</code> passed as a parameter.
	* </p>
	*
	* @param inputStream
	* The configuration input stream.
	* @param clazz
	* The class name, of the log4j configurator which will parse the <code>inputStream</code>. This must be a
	* subclass of {@link Configurator}, or null. If this value is null then a default configurator of
	* {@link PropertyConfigurator} is used.
	* @param hierarchy
	* The {@link org.apache.log4j.Hierarchy} to act on.
	* @since 1.2.17
	*/

	static
	public
	void selectAndConfigure(InputStream inputStream, String clazz, LoggerRepository hierarchy) {
	Configurator configurator = null;

	if(clazz != null) {
	LogLog.debug("Preferred configurator class: " + clazz);
	configurator = (Configurator) instantiateByClassName(clazz,
	Configurator.class,
	null);
	if(configurator == null) {
	LogLog.error("Could not instantiate configurator ["+clazz+"].");
	return;
	}
	} else {
	configurator = new PropertyConfigurator();
	}

	configurator.doConfigure(inputStream, hierarchy);
	}


	/**
	Configure log4j given a URL.

	<p>The url must point to a file or resource which will be interpreted by
	a new instance of a log4j configurator.

	<p>All configurations steps are taken on the
	<code>hierarchy</code> passed as a parameter.

	<p>
	@param url The location of the configuration file or resource.
	@param clazz The classname, of the log4j configurator which will parse
	the file or resource at <code>url</code>. This must be a subclass of
	{@link Configurator}, or null. If this value is null then a default
	configurator of {@link PropertyConfigurator} is used, unless the
	filename pointed to by <code>url</code> ends in '.xml', in which case
	{@link org.apache.log4j.xml.DOMConfigurator} is used.
	@param hierarchy The {@link org.apache.log4j.Hierarchy} to act on.

	@since 1.1.4 */

	static
	public
	void selectAndConfigure(URL url, String clazz, LoggerRepository hierarchy) {
	Configurator configurator = null;
	String filename = url.getFile();

	if(clazz == null && filename != null && filename.endsWith(".xml")) {
	clazz = "org.apache.log4j.xml.DOMConfigurator";
	}

	if(clazz != null) {
	LogLog.debug("Preferred configurator class: " + clazz);
	configurator = (Configurator) instantiateByClassName(clazz,
	Configurator.class,
	null);
	if(configurator == null) {
	LogLog.error("Could not instantiate configurator ["+clazz+"].");
	return;
	}
	} else {
	configurator = new PropertyConfigurator();
	}

	configurator.doConfigure(url, hierarchy);
	}
	}