Web框架学习:反射工具

2016-03-16

反射的作用

在Web框架中,反转控制(IOC)的实例化,依赖注入的赋值以及接口Handle函数的触发都是利用了反射机制,如同OC的字符串反射一样,Java里的反射也是通过类或Class进行内存的运行时(Runtime)操作.

反射的三个基本类

在Smart框架中,反射用到三个概念

Instance: 实例class.newInstance()来新建实例
Field: 成员变量field.set(Instance,value)来对具体实例的成员变量赋值
Method: 成员方法,使用method.invoke(Instance,args)触发某个成员方法

Example-ReflectionUtil

package org.smart4j.framework.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

public class ReflectionUtil {

    private static final Logger LOGGER = LoggerFactory.getLogger(ReflectionUtil.class);

    public static  Object newInstance(Class<?> cls) {
        Object instance = null;
        try {
            instance = cls.newInstance();
        } catch (InstantiationException e) {
            LOGGER.error("new instance failure",e);
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return instance;
    }

    public static Object invokeMethod(Object obj, Method method, Object args) {
        Object result = null;
        try {
            method.setAccessible(true);
            result = method.invoke(obj,args);
        } catch (IllegalAccessException e) {
            LOGGER.error("invoke method failure",e);
            throw new RuntimeException(e);
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        return result;
    }

    public static void setField(Object obj, Field field, Object value) {
        try {
            field.setAccessible(true);
            field.set(obj, value);
        } catch (IllegalAccessException e) {
            LOGGER.error("set field failure",e);
            throw new RuntimeException(e);
        }
    }
}