反射机制：java.lang.reflect
面向对象编程的基本特点：封装、继承和多态。因此下面的例子就用到了接口、抽象类和子类等。
Animal接口：
package com.taobao.demo;public interface Animal {void eat();void say();}AbstractAnimal抽象类：
package com.taobao.demo;public abstract class AbstractAnimal implements Animal {public String name;private Gender gender;public AbstractAnimal() {}public AbstractAnimal(String name, Gender gender) {this.name = name;this.gender = gender;}@Overridepublic void eat() {System.out.println("eat...");}@Overridepublic void say() {System.out.println("say...");}public String getName() {return name;}public void setName(String name) {this.name = name;}public Gender getGender() {return gender;}public void setGender(Gender gender) {this.gender = gender;}public enum Gender {MALE, FEMALE;}}Cat类：
package com.taobao.demo;public class Cat extends AbstractAnimal implements Animal {//给猫添加一个私有属性private Color eyeColor;public Cat() {}public Cat(String name, Gender gender, Color eyeColor) {super(name, gender);this.eyeColor = eyeColor;}@Overridepublic void eat() {System.out.println("I like to eat fish.");}@Overridepublic void say() {System.out.println("miao...miao...miao...");}public Color getEyeColor() {return eyeColor;}public void setEyeColor(Color eyeColor) {this.eyeColor = eyeColor;}public enum Color {WHITE,BLUE,YELLOW,BLACK;}}Dog类：
package com.taobao.demo;public class Dog extends AbstractAnimal implements Animal {//给狗添加一个私有属性private int age;public Dog() {}public Dog(String name, Gender gender, int age) {super(name, gender);this.age = age;}@Overridepublic void eat() {System.out.println("I like to eat bone.");}@Overridepublic void say() {System.out.println("wang...wang...wang...");}public void setAge(int age) {this.age = age;}public int getAge() {return age;}}上面这些类都是基础类，为了做实验用的基本类。也是为了实践而专门写的无意义的类。
AnimalFactory类：
package com.taobao.demo.factory;import com.taobao.demo.Animal;public class AnimalFactory {public static Animal getInstance(String className) throws InstantiationException, IllegalAccessException, ClassNotFoundException {return (Animal) Class.forName(className).newInstance();}}
测试反射实践：
package com.taobao.demo.reflect;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.Method;import com.taobao.demo.AbstractAnimal;import com.taobao.demo.Animal;import com.taobao.demo.Cat;import com.taobao.demo.factory.AnimalFactory;public class ReflectPractice {public static void main(String[] args) throws Exception {//所有类的对象都是Class的实例Class<?> clazz1 = Class.forName("com.taobao.demo.Cat");Class<?> clazz2 = new Cat().getClass();Class<?> clazz3 = Cat.class;//判断以上三个是不是同一个类System.out.println(clazz1.equals(clazz2) && clazz1.equals(clazz3));//输出类名System.out.println(clazz1.getName());//通过多种方式获得一个类的实例对象Cat cat0 = (Cat) clazz1.newInstance();Cat cat1 = new Cat();//通过class调用Cat类的构造方法，默认获得的构造方法的顺序比较奇怪Cat cat2 = (Cat) clazz1.getConstructors()[1].newInstance("miaomiao", AbstractAnimal.Gender.MALE, Cat.Color.YELLOW);//通过指定参数类型来获取对应的构造器Constructor<?> csr = clazz1.getConstructor(String.class, AbstractAnimal.Gender.class, Cat.Color.class);//打印该构造器的方法定义，返回值、参数类型等System.out.println(csr.toGenericString());//通过该构造器构造出实例对象Cat cat3 = (Cat) csr.newInstance("miaomiao", AbstractAnimal.Gender.MALE, Cat.Color.YELLOW);//获取父类和接口信息Class<?> superClass = clazz2.getSuperclass();System.out.println("父类名为："+superClass.getName());Class<?> clazz4 = Class.forName(clazz2.getSuperclass().getName());System.out.println(clazz4.getName());Class<?>[] interfaces = clazz3.getInterfaces();for(Class<?> interf: interfaces) {System.out.println(interf.getName());}//获取成员属性Field[] fields = clazz3.getDeclaredFields();for(Field field : fields) {System.out.println(field.getName());}//获取父类的属性，private和protected类型的获取不到Field[] fields2 = clazz3.getFields();System.out.println("父类属性"+fields2.length);for(Field field : fields2) {System.out.println(field);}//获取成员方法Method[] meths = clazz3.getMethods();for(Method method : meths) {System.out.println(method);}//调用其它类的方法Method method = clazz1.getMethod("say");Cat catt = (Cat) clazz1.newInstance();method.invoke(catt);method = clazz1.getMethod("setEyeColor", Cat.Color.class);method.invoke(catt, Cat.Color.YELLOW);System.out.println(catt.getEyeColor());//通过反射操作属性Field field = clazz1.getField("name");field.set(cat0, "xiaomao");System.out.println(field.get(cat0));//测试工厂方法Animal animal = AnimalFactory.getInstance("com.taobao.demo.Cat");animal.getClass().newInstance().say();}}