通过反射生成对象和调用方法

一、通过反射生成无参对象，通过反射调用有参方法

package com.ss.learn.chapter2;

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

public class ReflectServiceImpl {
	public void sayHello(String name) {
		System.out.println("Hello" + name);
	}
	
	public static void main(String[] args) {
		ReflectServiceImpl object = null;
		Method method;
		try {
			object = (ReflectServiceImpl) Class.forName("com.ss.learn.chapter2.ReflectServiceImpl").newInstance();
			method = object.getClass().getMethod("sayHello", String.class);
			method.invoke(object, "张三");
		} catch (InstantiationException | IllegalAccessException | ClassNotFoundException | NoSuchMethodException
				| SecurityException | IllegalArgumentException | InvocationTargetException e) {
			e.printStackTrace();
		}
	}
}

二、通过反射生成有参对象，通过反射调用无参函数

package com.ss.learn.chapter2;

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

public class ReflectServiceImpl2 {
	private String name;
	public ReflectServiceImpl2(String name) {
		this.name = name;
	}
	public void sayHello() {
		System.out.println("Hello" + name);
	}
	public static void main(String[] args) {
		ReflectServiceImpl2 object = null;
		try {
			object = (ReflectServiceImpl2) Class.forName("com.ss.learn.chapter2.ReflectServiceImpl2").getConstructor(String.class).newInstance("张三");
			Method method = object.getClass().getDeclaredMethod("sayHello");
			method.invoke(object);
		} catch (InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException
				| NoSuchMethodException | SecurityException | ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
}

三、拓展相关知识

用到的几个API：

.getConstructor(形参类.class , ....)

.getMethod(方法名, 形参.class)

.getDeclareMethod()

.invoke(实例, 参数) // 参数是对象没有的

/invoke(实例) // 实例里已经有实参

反射生成对象的时候

可以用变量Class<?> cls = Class.forName(类的全限定名)来保存类。

Class<?> cls = Class.forName("com.ss.learn.chapter2.ReflectServiceImpl2");
			object = (ReflectServiceImpl2) cls.getConstructor(String.class).newInstance("张三");
			Method method = cls.getDeclaredMethod("sayHello");
			method.invoke(object);

Class.forName(类的全限定名)  等价于 这个类的对象.getClass() 等价于  类名.class

说白了，就是这个“类”的Class实例