通过反射获取对象的值

 今天突然想到原先写过的一个反射类的效率问题，通过测试发现反射获取值的时间为直接获取值时间的9倍左右，于是加一个map缓存一部分结果，效率获得明显的提升取值时间大概为直接取值的三倍左右。

 

测试代码不贴了

测试结果

循环100000次

反射：890ms左右

加入map：300ms左右

直接调用：100ms左右

 

下面贴出改进代码

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

public class ReflectHelper {

	private static Map<Class<?>, Map<String, Field>> map = new HashMap<Class<?>, Map<String, Field>>();

	/**
	 * 获取obj对象fieldName的Field
	 * 
	 * @param obj
	 * @param fieldName
	 * @return
	 */
	public static Field getFieldByFieldName(Object obj, String fieldName) {
		Class<?> objClass = obj.getClass();
		Map<String, Field> cMap = map.get(objClass);
		if (cMap != null) {
			Field f = cMap.get(fieldName);
			if (f != null) {
				return f;
			}
		} else {
			cMap = new HashMap<String, Field>();
			map.put(objClass, cMap);
		}
		for (Class<?> superClass = objClass; superClass != Object.class; superClass = superClass.getSuperclass()) {
			try {
				Field field = superClass.getDeclaredField(fieldName);
				cMap.put(fieldName, field);
				return field;
			} catch (NoSuchFieldException e) {
			}
		}

		return null;
	}

	/**
	 * 获取obj对象fieldName的属性值
	 * 
	 * @param obj
	 * @param fieldName
	 * @return
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static Object getValueByFieldName(Object obj, String fieldName) throws SecurityException,
			NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
		Field field = getFieldByFieldName(obj, fieldName);
		Object value = null;
		if (field != null) {
			if (field.isAccessible()) {
				value = field.get(obj);
			} else {
				field.setAccessible(true);
				value = field.get(obj);
				field.setAccessible(false);
			}
		}
		return value;
	}

	/**
	 * 设置obj对象fieldName的属性值
	 * 
	 * @param obj
	 * @param fieldName
	 * @param value
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static void setValueByFieldName(Object obj, String fieldName, Object value) throws SecurityException,
			NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
		Field field = obj.getClass().getDeclaredField(fieldName);
		if (field.isAccessible()) {
			field.set(obj, value);
		} else {
			field.setAccessible(true);
			field.set(obj, value);
			field.setAccessible(false);
		}
	}
}