Java 反射之工厂模式

一.简单工厂模式

//接口package Factory;public interface Fruit {    public void eat(); //吃}

//实现接口类package Factory;public class Apple implements Fruit{    public Apple() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃苹果！");    }}package Factory;public class Banana implements Fruit{    public Banana() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃香蕉！");    }}

package Factory;public class Orange implements Fruit{    public Orange() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃橘子");    }}

//工厂类package Factory;public class Factory {    public Factory() {        // TODO Auto-generated constructor stub    }    public static Fruit getInstance(String className){        if("apple".equals(className))            return new Apple(); //返回一个对象        if("banana".equals(className))            return new Banana();        if("orange".equals(className))            return new Orange();        return null;    }}

//主方法package Factory;import java.util.Scanner;public class FactoryTest {    public FactoryTest() {        // TODO Auto-generated constructor stub    }    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner scanner=new Scanner(System.in);        String className=scanner.nextLine();//输入想要创建对象的名字       Fruit f=Factory.getInstance( className); //调用并接收      f.eat();    }}

运行结果：


这个工厂类是最简单的工厂类，可以体会到工厂模式的设计思想，但是每次想添加一个类都需要更改大量的代码，所以后来演变了一个更方便使用的工厂模式，利用反射机制创建对象，从而减少对代码的修改。

如果想再添加一个葡萄类
package Factory;

public class Grape implements Fruit{

public Grape() {    // TODO Auto-generated constructor stub}@Overridepublic void eat() {    // TODO Auto-generated method stub    System.out.println("吃葡萄！");}

}

//要在返回对象那多加一个创建葡萄类

package Factory;public class Factory {    public Factory() {        // TODO Auto-generated constructor stub    }    public static Fruit getInstance(String className){        if("apple".equals(className))            return new Apple();        if("banana".equals(className))            return new Banana();        if("orange".equals(className))            return new Orange();        if("grape".equals(className))            return new Grape(); //这里还要修改        return null;    }}

运行结果：

这样对代码的修改量会增大，这只是一个简单的工厂模式，若果放到一个项目当中那修改的代码量远远比这个要多很多。

二.反射之工厂模式

//接口package fanshe;public interface Fruit {    public void eat(); //吃}

//实现接口的类package fanshe;public class Apple implements Fruit {    public Apple() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃苹果~！");    }}

package fanshe;public class Banana implements Fruit{    public Banana() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃香蕉~！");    }}

package fanshe;public class Orange implements Fruit {    public Orange() {        // TODO Auto-generated constructor stub    }    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃橘子~！");    }}

//工厂类package fanshe;public class Factory {    public Factory() {        // TODO Auto-generated constructor stub    }    public static Fruit getInstance(String className)    {        /*if("orange".equals(className))            return new Orange();        return null;*/        Fruit fruit=null;        try {            fruit=(Fruit) Class.forName(className).newInstance();//创建对象        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return fruit;       }}

//主方法package fanshe;import java.util.Scanner;public class FactortDemo {    public FactortDemo() {        // TODO Auto-generated constructor stub    }    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner scanner=new Scanner(System.in);        String className=scanner.nextLine(); //输入想要创建类的名字     Fruit fruit=Factory.getInstance("fanshe."+className);     fruit.eat();    }}

运行结果：

如果再想添加一个葡萄类直接添加类就可以了，不用再修改其他代码，减少了代码的修改量

package fanshe;public class Grape implements Fruit{    public Grape() {        // TODO Auto-generated constructor stub    }    @Override    public void eat() {        // TODO Auto-generated method stub        System.out.println("吃葡萄~！");    }}

运行结果：