/*
 * 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.empire.commons;

import java.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.List;
import java.util.Locale;

import org.apache.commons.beanutils.MethodUtils;
import org.apache.empire.exceptions.EmpireException;
import org.apache.empire.exceptions.InternalException;
import org.apache.empire.exceptions.InvalidArgumentException;
import org.apache.empire.exceptions.ItemNotFoundException;
import org.apache.empire.exceptions.NotSupportedException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class contains common functions for comparing and converting values of type Object. 
 * 
 */
public final class ObjectUtils
{
    /**
     * This class explicitly defines that an Object has not been assigned a value.<BR>
     * This may be used in cases where the value of null may be a valid value.
     */
    private static final class NoValue implements Serializable
    {
        private static final long serialVersionUID = 1L;
        private NoValue()
        { /* dummy */
        }
        @Override
        public String toString()
        {
        	return "[NO-VALUE]";
        }
    }
    
    /**
     * Constant that defines a object of type NoValue.
     * This may be used in cases where the value of null is a valid value.
     */
    public static final NoValue NO_VALUE = new NoValue();
    
    // Logger
    private static final Logger log = LoggerFactory.getLogger(ObjectUtils.class);

    private static final String DATE_FORMAT = "yyyy-MM-dd";
	private static final String DATETIME_FORMAT = "yyyy-MM-dd HH:mm:ss";
	
    // DateOnly Formatter
    private static final ThreadLocal<SimpleDateFormat> dateOnlyFormatter = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue()
        {
            return new SimpleDateFormat(DATE_FORMAT);
        }
    };

    // DateTime Formatter
    private static final ThreadLocal<SimpleDateFormat> dateTimeFormatter = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue()
        {
            return new SimpleDateFormat(DATETIME_FORMAT);
        }
    };

    // Interal literal for NULL
    private static final String NULL = "NULL";
    
    private ObjectUtils()
    {
        // Static Function only
        // No instance may be created
    }
    
    /**
     * Checks whether an object has no value.
     * A Object is empty if and only if the Object is null or if its an empty string. 
     * @param o the object to check
     * @return true if the Object is null or if its an empty string. 
     */
    public static boolean isEmpty(Object o)
    {
        if (o==null || o==ObjectUtils.NO_VALUE)
            return true;
        if ((o instanceof String) && ((String)o).length()==0)
            return true;
        // not empty
        return false;
    }
    
    /**
     * Checks whether an object has a value.
     * A Object is considered to have a value if it is not null and not an empty string 
     * @param o the object to check
     * @return true if the Object is neither null nor an empty string. 
     */
    public static boolean isNotEmpty(Object o)
    {
        return !isEmpty(o);
    }
    
    /**
     * Checks whether a number is null or zero
     * @param value the number to check
     * @return true if the value is null or zero 
     */
    public static boolean isZero(Number value)
    {
        if (value==null)
            return true;
        if (value instanceof BigDecimal)
            return (BigDecimal.ZERO.compareTo((BigDecimal)value) == 0);
        if (value instanceof Float)
            return (((Float) value).compareTo(0.0f)==0);
        if (value instanceof Double)
            return (((Float) value).compareTo(0.0f)==0);
        if (value instanceof Long)
            return (value.longValue()==0l);
        // default: check int value
        return (value.intValue()==0);
    }

    /**
     * Checks whether a number is NOT null or zero
     * @param value the number to check
     * @return true if the value is NOT null or zero 
     */
    public static boolean isNonZero(Number value)
    {
        return !isZero(value);
    }
    
    /**
     * returns the string length of an object
     * @param o the object to check
     * @return the string length of the object
     */
    public static int lengthOf(Object o)
    {
        if (o==null || o==ObjectUtils.NO_VALUE)
            return 0;
        if ((o instanceof String))
            return ((String)o).length();
        // convert
        return o.toString().length();
    }
    
    /**
     * Compares two objects for equality 
     * 
     * @param o1 the first object
     * @param o2 the second object
     * 
     * @return true if both objects are equal or false otherwise
     */
    @SuppressWarnings("unchecked")
    public static boolean compareEqual(Object o1, Object o2)
    {
    	// simple case
    	if (o1==o2)
    		return true;
        // Check for Empty Values
        if (isEmpty(o1))
            return isEmpty(o2);
        if (isEmpty(o2))
            return isEmpty(o1);
        // Check classes
        if (o1.getClass().equals(o2.getClass()))
        {   // Check if object implements comparable
            if (o1 instanceof Comparable)
                return (((Comparable<Object>)o1).compareTo(o2)==0);
            else
                return o1.equals(o2);
        }
        // Classes don't match
        // Use equal check first
        if (o1.equals(o2) || o2.equals(o1))
            return true;
        // Compare Numbers
        if (o1 instanceof Number && o2 instanceof Number)
        {   // boolean test = obj1.equals(obj2);
            double d1 = ((Number)o1).doubleValue();
            double d2 = ((Number)o2).doubleValue(); 
            return (d1==d2);
        }
        // Enum
        if (o1 instanceof Enum<?>)
        {   // Special enum handling   
            if (o2 instanceof Number)
                return ((Enum<?>)o1).ordinal()==((Number)o2).intValue();
            // Compare Strings
            String strVal = StringUtils.coalesce(getString((Enum<?>)o1), NULL);
            return strVal.equals(getString(o2));
        }
        else if (o2 instanceof Enum<?>)
        {   // Special enum handling   
            if (o1 instanceof Number)
                return ((Enum<?>)o2).ordinal()==((Number)o1).intValue();
            // Compare Strings
            String strVal = StringUtils.coalesce(getString((Enum<?>)o2), NULL); 
            return strVal.equals(getString(o1));
        }
        // Compare Strings
        return o1.toString().equals(o2.toString());
    }

    /**
     * Compares two object arrrays for equality
     *
     * @param array1    the first array
     * @param array2    the second array
     *
     * @return true if both arrays are equal or false otherwise
     */
    public static boolean compareEqual(Object[] array1, Object[] array2)
    {   // Compare Length
        int len1 = (array1!=null ? array1.length : 0);
        int len2 = (array2!=null ? array2.length : 0);
        if (len1!= len2)
            return false;
        // Compare Key Values
        for (int i = 0; i < len1; i++)
        {   // Check String Values
            if (!ObjectUtils.compareEqual(array1[i], array2[i]))
                return false;
        }
        return true;
    }
    
    /**
     * Checks whether a preferred value is valid and returns an alternative value if not.
     * @param <T> the type of the values
     * @param preferred the preferred return value
     * @param alternative the alternative return value used if the preferred value is null 
     * @return the preferred value if it is not null or the alternative value otherwise
     */
    public static <T> T coalesce(T preferred, T alternative)
    {
        return (preferred!=null ? preferred : alternative);
    }

    /**
     * converts an object to an integer. If conversion is not possible, an error is thrown
     * @param v the value to convert
     * @return the integer value
     */
    public static int toInteger(Object v)
    {
        if (ObjectUtils.isEmpty(v))
            return 0;
        if (v instanceof Number)
            return ((Number)v).intValue();
        // Try to convert
        String str = v.toString();
        return Integer.parseInt(str);
    }
    
    /**
     * Converts an object value to an integer.
     * <P>
     * If the object value supplied is null or if conversion is not possible then the default value is returned.
     * @param v the obect to convert
     * @param defValue the default value if o is null or conversion is not possible 
     * @return the Integer value of o or a default value
     */
    public static int getInteger(Object v, int defValue)
    {
        // Check empty
        if (ObjectUtils.isEmpty(v))
            return defValue;
        // Try to convert
        try
        {   // Try to convert
            return toInteger(v);
        } catch (Exception e)
        {
        	log.warn(String.format("Cannot convert value [%s] to int!", v));
            return defValue;
        }
    }
    
    /**
     * Converts an object value to an integer.
     * <P>
     * If the object value supplied is null or if conversion is not possible then 0 is returned.
     * @param v the object value to convert
     * @return the Integer value of o or 0
     */
    public static int getInteger(Object v)
    {
        return getInteger(v, 0); 
    }

    /**
     * converts an object to a long. If conversion is not possible, an error is thrown
     * @param v the value to convert
     * @return the long value
     */
    public static long toLong(Object v)
    {
        if (ObjectUtils.isEmpty(v))
            return 0;
        if (v instanceof Number)
            return ((Number)v).longValue();
        // Try to convert
        String str = v.toString();
        return Long.parseLong(str);
    }
    
    /**
     * Converts an object value to a long.
     * <P>
     * If the object value supplied is null or if conversion is not possible then the default value is returned.
     * @param v the obect to convert
     * @param defValue the default value if o is null or conversion is not possible 
     * @return the Integer value of o or a default value
     */
    public static long getLong(Object v, long defValue)
    {
        // Check empty
        if (ObjectUtils.isEmpty(v))
            return defValue;
        // Try to convert
        try
        {   // Try to convert
            return toLong(v);
        } catch (Exception e)
        {
        	log.warn(String.format("Cannot convert value [%s] to long!", v));
            return defValue;
        }
    }
    
    /**
     * Converts an object value to a long.
     * <P>
     * If the object value supplied is null or if conversion is not possible then 0 is returned.
     * @param v the object value to convert
     * @return the Long value of o or 0
     */
    public static long getLong(Object v)
    {
        return getLong(v, 0); 
    }

    /**
     * converts an object to a double. If conversion is not possible, an error is thrown
     * @param v the value to convert
     * @return the double value
     */
    public static double toDouble(Object v)
    {
        // Get Double value
        if (ObjectUtils.isEmpty(v))
            return 0.0;
        if (v instanceof Number)
            return ((Number)v).doubleValue();
        // parse String for Integer value
        String val = v.toString(); 
        return Double.parseDouble(val);
    }
    
    /**
     * Converts an object value to a double.
     * <P>
     * If the object value supplied is null or if conversion is not possible then defValue is returned.
     * @param v the object value to convert
     * @param defValue the default value
     * @return the Long value of o or defValue
     */
    public static double getDouble(Object v, double defValue)
    {
        // Check empty
        if (ObjectUtils.isEmpty(v))
            return defValue;
        try
        {   // Try to convert
            return toDouble(v);
        } catch (Exception e)
        {
            log.warn(String.format("Cannot convert value [%s] to double!", v));
            return defValue;
        }
    }

    /**
     * Converts an object value to a double.
     * <P>
     * If the object value supplied is null or if conversion is not possible then 0.0 is returned.
     * @param v the object value to convert
     * @return the Long value of o or 0
     */
    public static double getDouble(Object v)
    {
        return getDouble(v, 0.0);
    }

    /**
     * converts an object to a decimal. If conversion is not possible, an error is thrown
     * @param v the value to convert
     * @return the decimal value
     */
    public static BigDecimal toDecimal(Object v)
    {
        // Get Double value
        if (ObjectUtils.isEmpty(v))
            return null;
        if (v instanceof BigDecimal)
            return ((BigDecimal)v);
        // Find a suitable converter
        if (v instanceof Number)
        {   // check other number types
            if (v instanceof BigInteger)
                return new BigDecimal((BigInteger)v);
            if (v instanceof Integer)
                return BigDecimal.valueOf(((Number)v).intValue());
            if (v instanceof Long)
                return BigDecimal.valueOf(((Number)v).longValue());
            // Default: convert via double
            return BigDecimal.valueOf(((Number)v).doubleValue());
        }
        // parse String for Integer value
        // Last-Chance > Try a string conversion
        return new BigDecimal(v.toString());
    }
    
    /**
     * Converts an object value to a BigDecimal.
     * <P>
     * If the object value supplied is null or if conversion is not possible then defValue is returned.
     * @param v the object value to convert
     * @param defValue the default value
     * @return the BigDecimal value of v or defValue
     */
    public static BigDecimal getDecimal(Object v, BigDecimal defValue)
    {
        // Check empty
        if (ObjectUtils.isEmpty(v))
            return defValue;
        try
        {   // Try to convert
            return toDecimal(v);
        } catch (Exception e)
        {   // Error
            log.warn(String.format("Cannot convert value [%s] to BigDecimal!", v));
            return defValue;
        }
    }

    /**
     * Converts an object value to a BigDecimal.
     * <P>
     * If the object value supplied is null or if conversion is not possible then 0.0 is returned.
     * @param v the object value to convert
     * @return the Long value of o or 0
     */
    public static BigDecimal getDecimal(Object v)
    {
        return getDecimal(v, BigDecimal.ZERO);
    }
    
    /**
     * Converts an object value to a boolean.
     * <P>
     * If the object value supplied is null or if conversion is not possible then false is returned.
     * @param v the object to convert
     * @return the boolean value of o (true or false)
     */
    public static boolean getBoolean(Object v)
    {
        // Get Boolean value
        if (ObjectUtils.isEmpty(v))
            return false;
        if (v instanceof Boolean)
            return ((Boolean)v).booleanValue();
        if (v instanceof Number)
            return (((Number)v).intValue()!=0);
        // parse String for boolean value
        String  val = v.toString(); 
        return (val.equalsIgnoreCase("Y") || val.equalsIgnoreCase("true"));
    }
    
    /**
     * Converts an object to an enum of the given type
     * @param enumType the enum type
     * @param value the value to convert
     * @return the enum
     */
    @SuppressWarnings("unchecked")
    public static <T extends Enum<?>> T getEnum(Class<T> enumType, Object value)
    {   // check for null
        if (isEmpty(value))
            return null;
        // check enum
        if (value instanceof Enum<?>)
        {   // already an enum: Check type
            if (value.getClass().equals(enumType))
                return (T)value;
            // try to match names
            value = ((Enum<?>)value).name();
        }
        // check column data type
        boolean numeric = (value instanceof Number);
        T[] items = enumType.getEnumConstants();
        if (items.length>0 && (items[0] instanceof EnumValue))
        {   // custom conversion
            for (T e : items)
            {
                Object eVal = ((EnumValue)e).toValue(numeric);
                if (ObjectUtils.compareEqual(eVal, value))
                    return e;
            }
            // error: not found
            throw new ItemNotFoundException(StringUtils.toString(value));
        }
        else if (numeric)
        {   // by ordinal
            int ordinal = ((Number)value).intValue();
            // check range
            if (ordinal<0 || ordinal>=items.length)
                throw new ItemNotFoundException(String.valueOf(ordinal));
            // return enum
            return items[ordinal]; 
        }
        else
        {   // by name
            String name = StringUtils.toString(value);
            // find name
            for (T e : items)
                if (e.name().equals(name))
                    return e;
            // error: not found
            throw new ItemNotFoundException(name);
        }
    }

    /**
     * find by name
     * @param enumType the enum type
     * @param name the enum name
     * @return the enum
     */
    public static <T extends Enum<?>> T getEnumByName(Class<T> enumType, String name)
    {   // check for null
        if (isEmpty(name))
            return null;
        // check column data type
        T[] items = enumType.getEnumConstants();
        for (T e : items)
            if (e.name().equals(name))
                return e;
        // error: not found
        throw new ItemNotFoundException(name);
    }
    
    /**
     * Convert Enum to Object
     */
    public static Object getEnumValue(Enum<?> enumValue, boolean isNumeric)
    {
        // convert
        if (enumValue instanceof EnumValue)
            return ((EnumValue)enumValue).toValue(isNumeric);
        // default
        return (isNumeric ? enumValue.ordinal() : getString(enumValue));
    }
    
    /**
     * Convert Enum to String
     */
    public static String getString(Enum<?> enumValue)
    {
        // convert
        if (enumValue instanceof EnumValue)
            return StringUtils.toString(((EnumValue)enumValue).toValue(false));
        /* special case */
        if (enumValue==null || enumValue.name().equals(NULL))
            return null;
        /* use name */
        return enumValue.name();
    }
    
    /**
     * Convert Object to String
     */
    public static String getString(Object value)
    {
        if (value==null)
            return null;
        if (value instanceof String)
            return (String)value;
        // convert
        if (value==NO_VALUE)
            throw new NotSupportedException(value, "getString");
        if (value instanceof Enum<?>)
            return getString((Enum<?>)value);
        if (value instanceof Date)
            return formatDate((Date)value, true);
        // default
        return value.toString();
    }
    
    /**
     * Converts an object value to a Date.
     * <P>
     * If the object value supplied is null or if conversion is not possible then null is returned.
     * @param v the object to convert
     * @param locale the locale used for conversion
     * @return the Date value of o or null
     */
    public static Date getDate(Object v, Locale locale)
    {
        // Get DateTime value
        if (ObjectUtils.isEmpty(v))
            return null;
        if (v instanceof Date)
            return ((Date)v);
        // Get Calendar
        if (v instanceof Number)
        {   // Get Date from a number
            long l = ((Number)v).longValue();
            if (l==0)
                return DateUtils.getDateNow();
            // Year or full date/time?
            /*
            if (l<10000)
            {   // Year only
                Calendar calendar = Calendar.getInstance(getSafeLocale(locale));
                calendar.set((int)l, 1, 1);
                return calendar.getTime();
            }
            */
            // Date from long
            return new Date(l);
        }
        // Try to parse
        return DateUtils.parseDate(v.toString(), locale);
    }
    
    /**
     * Converts an object value to a Date.
     * <P>
     * @param v the object to convert
     * @return the Date value of o or null
     */
    public static Date getDate(Object v)
    {
        // Get DateTime value
        if (ObjectUtils.isEmpty(v))
            return null;
        if (v instanceof java.util.Date)
            return ((java.util.Date)v);
        // Convert from String
        try
        {   String str = v.toString();
            if (str.length() > 10)
                return dateTimeFormatter.get().parse(str);
            else
                return dateOnlyFormatter.get().parse(str);
        } catch (Exception e)
        {
            log.error("Cannot convert value to date!", e);
            return null;
        }
    }
    
    /**
     * Formats a given date object to a standard date string.
     * The date string is locale independent and has the follwowing format:
     *  "yyyy-MM-dd hh:mm:ss"      
     * 
     * @param date the date to be formated
     * @param withTime indicates whether the date string should include the time or not
     * @return the date string
     */
    public static String formatDate(Date date, boolean withTime)
    {
    	if (withTime)
    		return dateTimeFormatter.get().format(date);
    	else
    		return dateOnlyFormatter.get().format(date);
    }
    
    /**
     * Generic conversion function that will convert a object to another value type.
     * 
     * @param <T> the type to convert to
     * @param c the class type to convert to
     * @param v the object to convert
     * 
     * @return the Date value of o or null
     * 
     * @throws ClassCastException if the object is not null and is not assignable to the type T.
     */
    @SuppressWarnings("unchecked")
    public static <T> T convert(Class<T> c, Object v)
        throws ClassCastException
    {
        if (v==null || c.isInstance(v))
            return (T)v;
        // Get Class form Primitive Type
        if (c.isPrimitive())
        {   // Get's the Java Class representing the primitive type
            c = (Class<T>) MethodUtils.getPrimitiveWrapper(c);
        }    
        // Convert
        if (c.isEnum())
        {   // convert to enum
            Object ev = getEnum((Class<? extends Enum<?>>)c, v); 
            return (T)ev;
        }
        if (c.isAssignableFrom(Boolean.class))
            return c.cast(getBoolean(v));
        if (c.isAssignableFrom(Integer.class))
            return c.cast(getInteger(v));
        if (c.isAssignableFrom(Long.class))
            return c.cast(getLong(v));
        if(c.isAssignableFrom(Double.class))
        	return c.cast(getDouble(v));
        if(c.isAssignableFrom(BigDecimal.class))
            return c.cast(getDecimal(v));
        if (c.isAssignableFrom(String.class))
            return c.cast(v.toString());
        // other
        return c.cast(v);
    }

    public static boolean isAssignmentCompatible(Class<?> target, Class<?> source)
    {
        // try plain assignment
        if (target.isAssignableFrom(source))
            return true;
        // Get Class form Primitive Type
        if (source.isPrimitive())
        {   // Get's the Java Class representing the primitive type
            source = MethodUtils.getPrimitiveWrapper(source);
            if (source == null)
                return false;
            if (target.isAssignableFrom(source))
                return true;
        }
        // Get Class form Primitive Type
        if (target.isPrimitive())
        {   // Get's the Java Class representing the primitive type
            target = MethodUtils.getPrimitiveWrapper(target);
            if (target == null)
                return false;
            if (target.isAssignableFrom(source))
                return true;
        }
        // Assume all numeric types can be converted to target class
        Class<Number> numberClass = Number.class;
        if (numberClass.isAssignableFrom(target) &&
            numberClass.isAssignableFrom(source))
        {   // Both are numeric
            return true;
        }
        // Special case: Allow character to string assignment
        if (source==Character.class && target==String.class)
        {
            return true;
        }    
        // Not compatible
        return false;
    }
    
    /**
     * Generic conversion function that will convert a list to another list type.
     * 
     * @param <T> the type of elements
     * @param t the type class
     * @param source the source collection
     * 
     * @return the new list type
     */
    public static <T> List<T> convert(Class<T> t, Collection<? extends T> source)
    {
        List<T> target = new ArrayList<T>();
        target.addAll(source);
        return target;
    }
    
    /**
     * Converts an Object array to a String array.
     * @param objArray the object array to convert
     * @param defValue default value which will be set for all null objects 
     * @return the String array
     */
    public static String[] toStringArray(Object[] objArray, String defValue)
    {
        if (objArray==null)
            return null;
        String[] strArray = new String[objArray.length];
        for (int i=0; i<objArray.length; i++)
        {
            if (objArray[i]!=null)
                strArray[i]=objArray[i].toString();
            else 
                strArray[i]=defValue;
        }
        return strArray;
    }
    
    /**
     * returns wheter or not a array contains a certain item
     * 
     * @param <T> the ype of the objects in the array
     * @param array the array to search
     * @param item the item to search for
     * 
     * @return true if the array contains the item or false otherwise
     */
    public static <T> boolean contains(T[] array, T item)
    {
        if (array==null)
            return false;
        for (int i=0; i<array.length; i++)
        {
            if (array[i]==item)
                return true;
            if (array[i]!=null && array[i].equals(item))
                return true;
        }
        return false;
    }

    /**
     * Retrieve a field value using reflection
     * @param clazz the class from which to obtain the field
     * @param object the object instance from which to obtain the field
     * @param property the property to obtain 
     * @param includePrivateFields flag whether or not to include private fields
     * @return the property value
     */
    public static synchronized Object getFieldValue(Class<?> clazz, Object object, String property, boolean includePrivateFields)
    {
        // check arguments
        if (clazz==null || (object!=null && !clazz.isInstance(object)))
            throw new InvalidArgumentException("clazz", clazz);
        if (StringUtils.isEmpty(property))
            throw new InvalidArgumentException("property", property);
        // begin
        boolean accessible = true; 
        Field field = null;
        try
        { // find and invoke
            field = (includePrivateFields ? clazz.getDeclaredField(property) : clazz.getField(property));
            accessible = field.isAccessible();
            if (includePrivateFields && accessible==false)
                field.setAccessible(true);
            // invoke
            return field.get(object);
        }
        catch (NoSuchFieldException e)
        {   // No such Method
            if (includePrivateFields)
            {   // try superclass
                clazz = clazz.getSuperclass();
                if (clazz!=null && !clazz.equals(java.lang.Object.class))
                    return getFieldValue(clazz, object, property, true);
            }
            // not found
            return null;
        }
        catch (IllegalAccessException e)
        {   // Invalid Method definition   
            throw new NotSupportedException(object, property, e);
        }
        finally {
            // restore accessible
            if (field!=null && accessible==false)
                field.setAccessible(false);
        }
    }

    /**
     * Retrieve a field value using reflection
     * The field accessor must be public
     * @param object the object instance from which to obtain the field
     * @param property the property to obtain 
     * @return the property value
     */
    public static Object getFieldValue(Object object, String property)
    {
        if (object==null)
            throw new InvalidArgumentException("object", object);
        // begin
        return getFieldValue(object.getClass(), object, property, false);
    }

    /**
     * Retrieve a field value using reflection 
     * @param object the object instance from which to obtain the field
     * @param property the property to obatin 
     * @return the property value
     */
    public static Object getPrivateFieldValue(Object object, String property)
    {
        if (object==null)
            throw new InvalidArgumentException("object", object);
        // begin
        return getFieldValue(object.getClass(), object, property, true);
    }
    
    /**
     * Invoke a simple method (without parameters) on an object using reflection
     * @param clazz the class from which to obtain the field
     * @param object the object instance on which to invoke the method
     * @param methodName the name of the method to invoke 
     * @param includePrivateMethods flag whether or not to include private methods
     * @return the return value of the method
     */
    public static synchronized Object invokeSimpleMethod(Class<?> clazz, Object object, String methodName, boolean includePrivateMethods)
    {
        // check arguments
        if (object==null)
            throw new InvalidArgumentException("object", object);
        if (clazz==null || !clazz.isInstance(object))
            throw new InvalidArgumentException("clazz", clazz);
        if (StringUtils.isEmpty(methodName))
            throw new InvalidArgumentException("methodName", methodName);
        // begin
        boolean accessible = true; 
        Method method = null;
        try
        { // find and invoke
            method = (includePrivateMethods ? clazz.getDeclaredMethod(methodName) : clazz.getMethod(methodName));
            accessible = method.isAccessible();
            if (includePrivateMethods && accessible==false)
                method.setAccessible(true);
            // invoke
            return method.invoke(object);
        }
        catch (NoSuchMethodException e)
        {   // No such Method
            if (includePrivateMethods)
            {   // try superclass
                clazz = clazz.getSuperclass();
                if (clazz!=null && !clazz.equals(java.lang.Object.class))
                    return invokeSimpleMethod(clazz, object, methodName, true);
            }
            // not found
            return null;
        }
        catch (SecurityException e)
        {   // Invalid Method definition   
            throw new NotSupportedException(object, methodName, e);
        }
        catch (IllegalAccessException e)
        {   // Invalid Method definition   
            throw new NotSupportedException(object, methodName, e);
        }
        catch (IllegalArgumentException e)
        {   // Invalid Method definition   
            throw new NotSupportedException(object, methodName, e);
        }
        catch (InvocationTargetException e)
        {   // Error inside Method
            Throwable cause = e.getCause();
            if (cause instanceof EmpireException)
                throw (EmpireException)cause;
            // wrap    
            throw new InternalException(cause);
        }
        finally {
            // restore accessible
            if (method!=null && accessible==false)
                method.setAccessible(false);
        }
    }

    /**
     * Invoke a simple method (without parameters) on an object using reflection
     * @param object the object instance on which to invoke the method
     * @param methodName the name of the method to invoke 
     * @return the return value of the method
     */
    public static Object invokeSimpleMethod(Object object, String methodName)
    {
        if (object==null)
            throw new InvalidArgumentException("object", object);
        // begin
        return invokeSimpleMethod(object.getClass(), object, methodName, false);
    }

    /**
     * Invoke a simple method (without parameters) on an object using reflection
     * @param object the object instance on which to invoke the method
     * @param methodName the name of the method to invoke 
     * @return the return value of the method
     */
    public static Object invokeSimplePrivateMethod(Object object, String methodName)
    {
        if (object==null)
            throw new InvalidArgumentException("object", object);
        // begin
        return invokeSimpleMethod(object.getClass(), object, methodName, true);
    }
    
}