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package org.fax4j.util;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

/**
 * Holds general functions for working with reflection and dynamic invocation
 * of code/classes. 
 * 
 * @author 	Sagie Gur-Ari
 * @version 1.0
 * @since	0.40.6
 */
public final class ReflectionHelper
{
	/**
	 * This is the default constructor.
	 */
	private ReflectionHelper()
	{
		super();
	}

	/**
	 * This function returns the thread context class loader.
	 * 
	 * @return	The thread context class loader
	 */
	public static ClassLoader getThreadContextClassLoader()
	{
		Thread thread=Thread.currentThread();
		ClassLoader classLoader=thread.getContextClassLoader();
		
		return classLoader;
	}
	
	/**
	 * This function returns the class based on the class name.
	 * 
	 * @param 	className
	 * 			The class name of the requested type
	 * @return	The type
	 * @throws	Exception
	 * 			Any exception during the loading of the type definition
	 */
	public static Class getType(String className) throws Exception
	{
		ClassLoader classLoader=ReflectionHelper.getThreadContextClassLoader();
		Class type=classLoader.loadClass(className);
		
		return type;
	}
	
	/**
	 * This function creates a new instance of the requested type.
	 * 
	 * @param 	type
	 * 			The class type
	 * @return	The instance
	 * @throws	Exception
	 * 			Any exception during the creation of the instance
	 */
	public static Object createInstance(Class type) throws Exception
	{
		//create instance
		Object instance=type.newInstance();
		
		return instance;
	}
	
	/**
	 * This function invokes the requested method.
	 * 
	 * @param 	type
	 * 			The class type
	 * @param 	instance
	 * 			The instance
	 * @param 	methodName
	 * 			The method name to invoke
	 * @param 	inputTypes
	 * 			An array of input types
	 * @param 	input
	 * 			The method input
	 * @return	The method output
	 * @throws	Exception
	 * 			Any exception while locating/running the method
	 */
	public static Object invokeMethod(Class type,Object instance,String methodName,Class[] inputTypes,Object[] input) throws Exception
	{
		//get method
		Method method=type.getMethod(methodName,inputTypes);

		//set accessible
		method.setAccessible(true);

		//invoke method
		Object output=method.invoke(instance,input);
		
		return output;
	}
	
	/**
	 * This function returns the field wrapper for the requested field
	 * 
	 * @param 	type
	 * 			The class type
	 * @param	fieldName
	 * 			The field name
	 * @return	The field
	 * @throws	Exception
	 * 			Any exception while locating/running the method
	 */
	public static Field getField(Class type,String fieldName) throws Exception
	{
		//get field
		Field field=type.getDeclaredField(fieldName);

		//set accessible
		field.setAccessible(true);

		return field;
	}
}