工厂模式

1. 工厂模式 (Factory Pattern)

核心目的：创建对象

专注于如何创建对象，隐藏对象创建的复杂细节。

典型实现：

java

// 产品接口
public interface Payment {
    void pay(BigDecimal amount);
}

// 具体产品
public class WechatPay implements Payment {
    public void pay(BigDecimal amount) {
        System.out.println("微信支付: " + amount);
    }
}

public class Alipay implements Payment {
    public void pay(BigDecimal amount) {
        System.out.println("支付宝: " + amount);
    }
}

// 工厂类 - 负责创建对象
public class PaymentFactory {
    public static Payment createPayment(PaymentType type) {
        switch (type) {
            case WECHAT_PAY:
                return new WechatPay();
            case ALIPAY:
                return new Alipay();
            default:
                throw new IllegalArgumentException("不支持的支付类型");
        }
    }
}

// 使用
Payment payment = PaymentFactory.createPayment(PaymentType.WECHAT_PAY);
payment.pay(new BigDecimal("100.00"));

工厂模式使用Spring Bean的几种方式

方式1：工厂类本身是Spring Bean

java

@Component
public class PaymentFactory {
    
    @Autowired
    private WechatPay wechatPay;
    
    @Autowired
    private Alipay alipay;
    
    @Autowired
    private BankCardPay bankCardPay;
    
    public Payment createPayment(PaymentType type) {
        switch (type) {
            case WECHAT_PAY:
                return wechatPay;  // 返回Spring管理的Bean
            case ALIPAY:
                return alipay;
            case BANK_CARD:
                return bankCardPay;
            default:
                throw new IllegalArgumentException("不支持的支付类型");
        }
    }
}

方式2：使用ApplicationContext

java

@Component
public class PaymentFactory {
    
    @Autowired
    private ApplicationContext applicationContext;
    
    public Payment createPayment(PaymentType type) {
        switch (type) {
            case WECHAT_PAY:
                return applicationContext.getBean(WechatPay.class);
            case ALIPAY:
                return applicationContext.getBean(Alipay.class);
            case BANK_CARD:
                return applicationContext.getBean(BankCardPay.class);
            default:
                throw new IllegalArgumentException("不支持的支付类型");
        }
    }
}

方式3：使用@Bean方法工厂（配置类方式）

java

@Configuration
public class PaymentConfig {
    
    @Bean
    @ConditionalOnProperty(name = "payment.wechat.enabled", havingValue = "true")
    public WechatPay wechatPay() {
        return new WechatPay();
    }
    
    @Bean
    @ConditionalOnProperty(name = "payment.alipay.enabled", havingValue = "true")
    public Alipay alipay() {
        return new Alipay();
    }
    
    @Bean
    public PaymentFactory paymentFactory(List<Payment> payments) {
        return new PaymentFactory(payments);
    }
}