ReflectionUtils.java

package com.cabletech.common.util;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.Assert;

/**
 * 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.
 * 
 * @author calvin
 */
public class ReflectionUtils {
 
	private static Logger logger = LoggerFactory.getLogger(ReflectionUtils.class);

	/**
	 * 调用Getter方法. 
	 * @param obj obj
	 * @param propertyName propertyName
	 * @return
	 */
	public static Object invokeGetterMethod(Object obj, String propertyName) {
		String getterMethodName = "get" + StringUtils.capitalize(propertyName);
		return invokeMethod(obj, getterMethodName, new Class[] {}, new Object[] {});
	}

	/**
	 * 调用Setter方法.使用value的Class来查找Setter方法.
	 * @param obj obj
	 * @param propertyName propertyName
	 * @param value value
	 */
	public static void invokeSetterMethod(Object obj, String propertyName, Object value) {
		invokeSetterMethod(obj, propertyName, value, null);
	}


	/**
	 * 调用Setter方法.
	 * @param obj obj
	 * @param propertyName propertyName
	 * @param value value
	 * @param propertyType propertyType
	 */
	public static void invokeSetterMethod(Object obj, String propertyName, Object value, Class<?> propertyType) {
		Class<?> type = propertyType != null ? propertyType : value.getClass();
		String setterMethodName = "set" + StringUtils.capitalize(propertyName);
		invokeMethod(obj, setterMethodName, new Class[] { type }, new Object[] { value });
	}


	/**
	 * 直接读取对象属性值 无视private/protected修饰符 不经过getter函数.
	 * @param obj obj
	 * @param fieldName fieldName
	 * @return
	 */
	public static Object getFieldValue(final Object obj, final String fieldName) {
		Field field = getAccessibleField(obj, fieldName);

		if (field == null) {
			throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + obj + "]");
		}

		Object result = null;
		try {
			result = field.get(obj);
		} catch (IllegalAccessException e) {
			logger.error("不可能抛出的异常{}", e.getMessage());
		}
		return result;
	}

	/**
	 * 直接设置对象属性值 无视private/protected修饰符 不经过setter函数.
	 * @param obj obj
	 * @param fieldName fieldName
	 * @param value value
	 */
	public static void setFieldValue(final Object obj, final String fieldName, final Object value) {
		Field field = getAccessibleField(obj, fieldName);

		if (field == null) {
			throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + obj + "]");
		}

		try {
			field.set(obj, value);
		} catch (IllegalAccessException e) {
			logger.error("不可能抛出的异常:{}", e.getMessage());
		}
	}

	/**
	 * 循环向上转型, 获取对象的DeclaredField
	 * 如向上转型到Object仍无法找到 返回null.
	 * @param obj obj
	 * @param fieldName fieldName
	 * @return
	 */
	public static Field getAccessibleField(final Object obj, final String fieldName) {
		Assert.notNull(obj, "object不能为空");
		Assert.hasText(fieldName, "fieldName");
		for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()) {
			try {
				Field field = superClass.getDeclaredField(fieldName);
				field.setAccessible(true);
				return field;
			} catch (NoSuchFieldException e) {//NOSONAR
				// Field不在当前类定义继续向上转型
			}
		}
		return null;
	}


	/**
	 *  直接调用对象方法, 无视private/protected修饰符
	 * 用于属性调用的情况.
	 * @param obj obj
	 * @param methodName methodName
	 * @param parameterTypes parameterTypes
	 * @param args args
	 * @return
	 */
	public static Object invokeMethod(final Object obj, final String methodName, final Class<?>[] parameterTypes,
			final Object[] args) {
		Method method = getAccessibleMethod(obj, methodName, parameterTypes);
		if (method == null) {
			throw new IllegalArgumentException("Could not find method [" + methodName + "] on target [" + obj + "]");
		}

		try {
			return method.invoke(obj, args);
		} catch (Exception e) {
			throw convertReflectionExceptionToUnchecked(e);
		}
	}


	/**
	 * 
	 * 循环向上转型, 获取对象的DeclaredMethod,并强制设置为可访问
	 * 如向上转型到Object仍无法找到 返回null.
	 * 
	 * 用于方法被多次调用的情况. 先使用本函数先取得Method,然后调用Method.invoke(Object obj, Object... args)
	 * @param obj obj
	 * @param methodName methodName
	 * @param parameterTypes parameterTypes
	 * @return
	 */
	public static Method getAccessibleMethod(final Object obj, final String methodName,
			final Class<?>... parameterTypes) {
		Assert.notNull(obj, "object不能为空");

		for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()) {
			try {
				Method method = superClass.getDeclaredMethod(methodName, parameterTypes);

				method.setAccessible(true);

				return method;

			} catch (NoSuchMethodException e) {//NOSONAR
				// Method不在当前类定义继续向上转型
			}
		}
		return null;
	}

	/**
	 * 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 <T> t
	 * @param clazz The class to introspect
	 * @return the first generic declaration, or Object.class if cannot be determined
	 */
	@SuppressWarnings("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("unchecked")
	public static Class getSuperClassGenricType(final Class clazz, final int index) {

		Type genType = clazz.getGenericSuperclass();

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

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

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

		return (Class) params[index];
	}

	/**
	 * 将反射时的checked exception转换为unchecked exception.
	 * @param e e
	 * @return
	 */
	public static RuntimeException convertReflectionExceptionToUnchecked(Exception e) {
		if (e instanceof IllegalAccessException || e instanceof IllegalArgumentException
				|| e instanceof NoSuchMethodException) {
			return new IllegalArgumentException("Reflection Exception.", e);
		} else if (e instanceof InvocationTargetException) {
			return new RuntimeException("Reflection Exception.", ((InvocationTargetException) e).getTargetException());
		} else if (e instanceof RuntimeException) {
			return (RuntimeException) e;
		}
		return new RuntimeException("Unexpected Checked Exception.", e);
	}
}