定義

抽象工廠模式提供一個(gè)創(chuàng)建一系列相關(guān)或相互依賴對(duì)象的接口，而無需指定它們具體的類

角色

• 抽象產(chǎn)品類A
• 抽象產(chǎn)品類B
• 抽象工廠類
• 具體工廠類C（生成A）
• 具體工廠類D（生產(chǎn)B）

UML類圖

抽象工廠模式UML類圖

代碼

• IBenz.java

public interface IBenz {
    void run();
}

• IBWM.java

public interface IBWM {
    void run();
}

• HomeUseBenz.java

public class HomeUseBenz implements IBenz {
    @Override
    public void run() {
        System.out.println("first.HomeUseBenz run");
    }
}

• HomeUseBWM.java

public class HomeUseBWM implements IBWM {
    @Override
    public void run() {
        System.out.println("first.HomeUseBWM run");
    }
}

• BusinessUseBenz.java

public class BusinessUseBenz implements IBenz {
    @Override
    public void run() {
        System.out.println("first.BusinessUseBenz run");
    }
}

• BusinessUseBWM.java

public class BusinessUseBWM implements IBWM {
    @Override
    public void run() {
        System.out.println("first.BusinessUseBWM run");
    }
}

• AbstarctFactory.java

public abstract class AbstarctFactory {
    public abstract IBWM createBWM();
    public abstract IBenz createBenz();
}

• HomeUseFactory.java

public class HomeUseFactory extends AbstarctFactory {
    @Override
    public IBWM createBWM() {
        return new HomeUseBWM();
    }
    @Override
    public IBenz createBenz() {
        return new HomeUseBenz();
    }
}

• BusinessFactory.java

public class BusinessFactory extends AbstarctFactory {
    @Override
    public IBWM createBWM() {
        return new BusinessUseBWM();
    }              
    @Override
    public IBenz createBenz() {
        return new BusinessUseBenz();
    }
}

抽象工廠模式的優(yōu)點(diǎn)

• 1 易于交換產(chǎn)品系列，由于具體工廠類，在一個(gè)應(yīng)用中只需要在初始化的時(shí)候出現(xiàn)一次，這就使得改變一個(gè)應(yīng)用的具體工廠變得非常容易，它只需要改變具體工廠即可使用不同的產(chǎn)品配置
• 2 它讓具體的創(chuàng)建實(shí)例的過程與客戶端分離，客戶端是通過它們的抽象接口操作實(shí)例，產(chǎn)品的具體類名也被具體工廠的實(shí)現(xiàn)分離，不會(huì)出現(xiàn)在客戶代碼中

抽象工廠模式的缺點(diǎn)

如果想要增加一個(gè)不同的車型，則需要增加三個(gè)類以及修改三個(gè)工廠，比較繁瑣！

使用簡(jiǎn)單工廠改進(jìn)抽象工廠

UML類圖

簡(jiǎn)單工廠改進(jìn)抽象工廠UML.png

代碼

• AllFactory.java

public class AllFactory {
    private static final String type = "home";
    //private static final String type = "business";
    public static IBenz createBenz(){
        IBenz benz = null;
        switch (type){
            case "home":
                benz = new HomeUseBenz();
                break;
            case "business":
                benz = new BusinessUseBenz();
                break;
        }
        return benz;
    }
    public static IBWM createBWM(){
        IBWM bwm = null;
        switch (type){
            case "home":
                bwm = new HomeUseBWM();
                break;
            case "business":
                bwm = new BusinessUseBWM();
                break;
        }
        return bwm;
    }
}

使用反射改進(jìn)抽象工廠方法

public class AllFactory {
    private final static String type="homeUse";
    //private final static String type="businessUse";

    public static IBenz createBenz() throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        String className = type.substring(0, 1).toUpperCase() + type.substring(1) + "Benz";
        //獲取包路徑
        String packageName = new Object() {
            public String getPackageName() {
                return this.getClass().getPackage().getName();
            }
        }.getPackageName();
        Class<? extends IBenz> clazz = (Class<? extends IBenz>) Class.forName(packageName+"."+className);
        return clazz.newInstance();
    }
    public static IBWM createBWM() throws IllegalAccessException, InstantiationException, ClassNotFoundException {
        String className = type.substring(0, 1).toUpperCase() + type.substring(1) + "BWM";
        //獲取包路徑
        String packageName = new Object() {
            public String getPackageName() {
                return this.getClass().getPackage().getName();
            }
        }.getPackageName();
        Class<? extends IBWM> clazz = (Class<? extends IBWM>) Class.forName(packageName +"."+className);
        return clazz.newInstance();
    }
}