工厂模式 | 易学教程

例子1：开发一个类似植物大战僵尸的游戏，有三种不同的植物：绿豆，蓝冰，坚果

　　分析：可以使用简单工厂模式：因为每个植物都需使用new（）方法创建实例，所以我们将所以不同的植物实现一个名叫植物的接口，然后在在工厂类中判断所需创建的植物，若要创建指定的植物只需调用工厂类中的createPlant方法即可

package org.imooc.factory;

import org.imooc.component.Arms;
import org.imooc.component.Hair;
import org.imooc.component.Shell;
import org.imooc.plant.*;

public class SimpleFactory {
    
       /**
    * 创建植物对象的静态方法
    */
   public static Plant createPlant(String name) {
       Plant plant = null;
       if(PlantNameConstant.BEAN_NAME.equals(name)) {
           plant = new Bean();
       } else if (PlantNameConstant.ICE_NAME.equals(name)) {
           plant = new Ice();
       } else if (PlantNameConstant.WALL_NAME.equals(name)) {
           plant = new Wall();
       }
       return plant;
   }

    public static Plant createPlantByClassName(String name) throws Exception {                  //使用反射可使代码更加简洁
        return (Plant)Class.forName(name).newInstance();
    }
}

例子2：开发一个类似植物大战僵尸的游戏，有三种不同的植物：绿豆，蓝冰，坚果；每个植物有不同的装备和武器

　　分析：此时再使用上述的简单工厂模式会使原来代码变为以下样子：

package org.imooc.factory;

import org.imooc.component.Arms;
import org.imooc.component.Hair;
import org.imooc.component.Shell;
import org.imooc.plant.*;

public class SimpleFactory {

    /**
     * 创建植物对象的静态方法
     */
    public static Plant createPlant(String name) {
        Plant plant = null;
        if(PlantNameConstant.BEAN_NAME.equals(name)) {
            Bean bean = new Bean();
            Hair hair = new Hair();
            hair.setColor("绿色");
            bean.setHair(hair);
            Arms arms = new Arms();
            arms.setBulletType("普通的豆子");
            bean.setArms(arms);
            plant = bean;
        } else if (PlantNameConstant.ICE_NAME.equals(name)) {
            Ice ice = new Ice();
            Hair hair = new Hair();
            hair.setColor("蓝色");
            ice.setHair(hair);
            Arms arms = new Arms();
            arms.setBulletType("冰冻的豆子");
            ice.setArms(arms);
            plant = ice;
        } else if (PlantNameConstant.WALL_NAME.equals(name)) {
            Wall wall = new Wall();
            Shell shell = new Shell();
            shell.setHardness(5);
            wall.setShell(shell);
            plant = wall;
        } else if ("new_Wall".equals(name)) {
            Wall wall = new Wall();
            Shell shell = new Shell();
            shell.setHardness(10);
            wall.setShell(shell);
            plant = wall;
        }
        return plant;
    }

}

　　分析：此时代码变得过于复杂且复用性会变差，所以便可以把每个植物设为工厂类并且实现一个公共的工厂接口（都需要有create（）方法），然后再由一个总工厂来创建这些植物工厂：

绿豆植物的工厂类：

package org.imooc.factory;

import org.imooc.component.Arms;
import org.imooc.component.Hair;
import org.imooc.plant.Bean;
import org.imooc.plant.Plant;

public class BeanFactory implements Factory {
    public Plant createPlant() {
        Bean bean = new Bean();
        Hair hair = new Hair();
        hair.setColor("绿色");
        bean.setHair(hair);
        Arms arms = new Arms();
        arms.setBulletType("普通的豆子");
        bean.setArms(arms);
        return bean;
    }
}

蓝冰植物的工厂类：

package org.imooc.factory;

import org.imooc.component.Arms;
import org.imooc.component.Hair;
import org.imooc.plant.Ice;
import org.imooc.plant.Plant;

public class IceFactory implements Factory {
    public Plant createPlant() {
        Ice ice = new Ice();
        Hair hair = new Hair();
        hair.setColor("蓝色");
        ice.setHair(hair);
        Arms arms = new Arms();
        arms.setBulletType("冰冻的豆子");
        ice.setArms(arms);
        return ice;
    }
}

坚果植物的工厂类：

package org.imooc.factory;

import org.imooc.component.Shell;
import org.imooc.plant.Plant;
import org.imooc.plant.Wall;

public class WallFactory implements Factory {
    public Plant createPlant() {
        Wall wall = new Wall();
        Shell shell = new Shell();
        shell.setHardness(5);
        wall.setShell(shell);
        return wall;
    }
}

所以植物类需实现的接口：

package org.imooc.factory;

import org.imooc.plant.Plant;

public interface Factory {
    public Plant createPlant();
}

创建植物工厂的总工厂类：

package org.imooc.factory;

import org.imooc.plant.PlantNameConstant;

public class  FactoryBuilder {
    public static Factory build(String name) {
        Factory factory = null;
        if(PlantNameConstant.BEAN_NAME.equals(name)) {
            factory = new BeanFactory();
        } else if (PlantNameConstant.ICE_NAME.equals(name)) {
            factory = new IceFactory();
        } else if (PlantNameConstant.WALL_NAME.equals(name)) {
            factory = new WallFactory();
        }
        return factory;
    }

    public static Factory buildByClassName(String name) throws Exception {
        return (Factory)Class.forName(name).newInstance();
    }
}