BeanFactoryAware

BeanFactoryAware是Spring提供的Aware接口之一，用于让Bean获取BeanFactory引用。

接口定义

public interface BeanFactoryAware extends Aware {
    void setBeanFactory(BeanFactory beanFactory) throws BeansException;
}

实现示例

@Component
public class MyBeanFactoryAwareBean implements BeanFactoryAware {

    private BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }

    public void doSomething() {
        // 通过BeanFactory获取其他Bean
        UserService userService = beanFactory.getBean(UserService.class);

        // 检查Bean是否存在
        if (beanFactory.containsBean("orderService")) {
            OrderService orderService = beanFactory.getBean("orderService", OrderService.class);
        }

        // 获取Bean别名
        String[] aliases = beanFactory.getAliases("userService");

        // 判断是否单例
        boolean isSingleton = beanFactory.isSingleton("userService");
    }
}

调用时机

┌─────────────────────────────────────┐
│  Bean实例化                          │
├─────────────────────────────────────┤
│  属性注入                            │
├─────────────────────────────────────┤
│  Aware接口回调 ← 此时调用             │
│  (BeanFactoryAware.setBeanFactory)  │
├─────────────────────────────────────┤
│  BeanPostProcessor前置处理           │
├─────────────────────────────────────┤
│  InitializingBean.afterPropertiesSet │
├─────────────────────────────────────┤
│  @PostConstruct                      │
├─────────────────────────────────────┤
│  BeanPostProcessor后置处理           │
└─────────────────────────────────────┘

BeanFactory常用方法

// 获取Bean
Object getBean(String name);
T getBean(Class<T> requiredType);
T getBean(String name, Class<T> requiredType);

// 获取Provider（延迟获取）
ObjectProvider<T> getBeanProvider(Class<T> requiredType);

// 包含Bean判断
boolean containsBean(String name);

// 单例/原型判断
boolean isSingleton(String name);
boolean isPrototype(String name);

// 类型判断
boolean isTypeMatch(String name, Class<?> type);

// 获取类型
Class<?> getType(String name);

// 获取别名
String[] getAliases(String name);

与@Autowired对比

优先使用@Autowired，仅在需要容器功能时使用BeanFactoryAware。

使用场景

@Component
public class DynamicBeanLoader implements BeanFactoryAware {

    private BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }

    // 根据条件动态获取Bean
    public Object getBeanByType(String beanType) {
        switch (beanType) {
            case "user":
                return beanFactory.getBean(UserService.class);
            case "order":
                return beanFactory.getBean(OrderService.class);
            default:
                return beanFactory.getBean("defaultService");
        }
    }

    // 检查Bean可用性
    public boolean isServiceAvailable(String serviceName) {
        return beanFactory.containsBean(serviceName);
    }
}

要点总结

• BeanFactoryAware让Bean获取BeanFactory引用
• setBeanFactory在属性注入后、初始化前调用
• 可用于动态获取Bean、检查Bean存在性
• 优先使用@Autowired声明式注入
• 需容器级别操作时才使用此接口