ReflectionUtils.java

/*
 * @(#)ReflectionUtils.java 2012-8-1 下午10:00:00
 *
 * Copyright (c) 2011-2012 Makersoft.org all rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *
 */
package org.makersoft.shards.utils;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;

/**
 * 反射工具类.
 * 
 * 提供访问私有变量,获取泛型类型Class, 提取集合中元素的属性, 转换字符串到对象等Util函数.
 * 
 */
public class ReflectionUtils {

	private static final Log log = LogFactory.getLog(ReflectionUtils.class);
	
	private ReflectionUtils(){
		
	}
	
	/**
	 * 通过反射, 获得Class定义中声明的父类的泛型参数的类型. 如无法找到, 返回Object.class. eg. public UserDao
	 * extends HibernateDao<User>
	 * 
	 * @param clazz
	 *            The class to introspect
	 * @return the first generic declaration, or Object.class if cannot be
	 *         determined
	 */
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public static <T> Class<T> getSuperClassGenricType(final Class clazz) {
		return getSuperClassGenricType(clazz, 0);
	}

	/**
	 * 通过反射, 获得Class定义中声明的父类的泛型参数的类型. 如无法找到, 返回Object.class.
	 * 
	 * 如public UserDao extends HibernateDao<User,Long>
	 * 
	 * @param clazz
	 *            clazz The class to introspect
	 * @param index
	 *            the Index of the generic ddeclaration,start from 0.
	 * @return the index generic declaration, or Object.class if cannot be
	 *         determined
	 */
	@SuppressWarnings("rawtypes")
	public static Class getSuperClassGenricType(final Class clazz,
			final int index) {

		Type genType = clazz.getGenericSuperclass();

		if (!(genType instanceof ParameterizedType)) {
			log.warn(clazz.getSimpleName()+ "'s superclass not ParameterizedType");
			return Object.class;
		}

		Type[] params = ((ParameterizedType) genType).getActualTypeArguments();

		if (index >= params.length || index < 0) {
			log.warn("Index: " + index + ", Size of "
					+ clazz.getSimpleName() + "'s Parameterized Type: "
					+ params.length);
			return Object.class;
		}
		if (!(params[index] instanceof Class)) {
			log.warn(clazz.getSimpleName()
					+ " not set the actual class on superclass generic parameter");
			return Object.class;
		}

		return (Class) params[index];
	}
}