利用反射实现简单工厂类，可以任意增加子类

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1.基础的简单工厂类

//简单工厂设计模式interface Vehicle        //写一个接口，但是我更喜欢叫它标准，所有符合这个标准的类均归为同一类{    public void howToWork();}class Car implements Vehicle      //汽车类实现交通工具接口（或者说是汽车类符合交通工具标准）{    public void howToWork()    {        System.out.println("开车去!");    }}class Bike implements Vehicle {    public void howToWork()    {        System.out.println("骑车去!");    }}class Airplane implements Vehicle{    public void howToWork()    {        System.out.println("坐飞机去!");    }}class Factory             //工厂类{     public static Vehicle create(String vehicle)  //实现一个静态方法用于创建实例    {        Vehicle sample = null;        switch(vehicle)        {            case "car":                sample = new Car();                break;            case "bike":                sample = new Bike();                break;            case "airplane" :                sample = new Airplane();                break;        }        return sample;    }}public class SimpleFactory{    public static void main(String args[])    {        Vehicle vehicle = Factory.create(args[0]);        vehicle.howToWork();    }}

2.利用反射实现简单工厂类的解耦合

package reflect;//工厂设计模式升级版，简单工厂也可以解决之前难以维护的问题interface Fruit // 定义接口{public void eat();}class Apple implements Fruit{@Overridepublic void eat(){// TODO Auto-generated method stubSystem.out.println("eat Apple");}}class Banana implements Fruit{@Overridepublic void eat(){// TODO Auto-generated method stubSystem.out.println("eat Banana");}}class Orange implements Fruit{@Overridepublic void eat(){// TODO Auto-generated method stubSystem.out.println("eat Orange");}}class Factory{public static Fruit getInstance(String className) throws Exception{Fruit f = null;f = (Fruit) Class.forName(className).newInstance();  //利用反射实现实例化Fruit的子类return f;}}public class TestFactory{public static void main(String[] args) throws Exception{// TODO Auto-generated method stubFruit f = Factory.getInstance("reflect.Orange");f.eat();}}

3.总结：

基础的简单工厂类最大的问题就是新增子类后，修改代码的问题，但是有了反射机制的引入，实现了可以任意增加子类且不会增加代码的维护难度。

4.使用属性配置文件让类的创建更加灵活

还是拿水果来举例子

Fruit.java

package cn.limbo.study;/** * Created by limbo on 2016/10/31. */public interface Fruit {    void eat();}

Apple.java

package cn.limbo.study;/** * Created by limbo on 2016/10/31. */public class Apple implements Fruit {    @Override    public void eat() {        System.out.println("eat apple");    }}

Orange.java

package cn.limbo.study;/** * Created by limbo on 2016/10/31. */public class Orange implements Fruit {    @Override    public void eat() {        System.out.println("Orange");    }}

FruitFactory.java

package cn.limbo.study;/** * Created by limbo on 2016/10/31. */public class FruitFactory {    public static Fruit getFruit(String className) throws ClassNotFoundException, IllegalAccessException, InstantiationException {        Fruit fruit = (Fruit) Class.forName(className).newInstance();        return fruit;    }}

ReadProperties.java

package cn.limbo.study;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.Properties;/** * Created by limbo on 2016/10/31. */public class ReadProperties {    public static Properties getProperties() throws IOException {        Properties pro = new Properties();        File f = new File("src/fruit.properties");        if(f.exists()) {            pro.load(new FileInputStream(f));        }else{            System.out.println("null");        }        return pro;    }}

fruit.properties

apple=cn.limbo.study.Appleorange=cn.limbo.study.Orange

test.java

 @Test    public void eatFruit() {        Properties pro = null;        Fruit apple = null;        try {            pro = ReadProperties.getProperties();            apple = FruitFactory.getFruit(pro.getProperty("apple"));        } catch (IOException e) {            e.printStackTrace();        } catch (IllegalAccessException e) {            e.printStackTrace();        } catch (InstantiationException e) {            e.printStackTrace();        } catch (ClassNotFoundException e) {            e.printStackTrace();        }        if(apple != null){            apple.eat();        }else{            System.out.println("null");        }    }

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