簡介

spring在創(chuàng)建當(dāng)前bean時，會去調(diào)用ApplicationContextAware接口的擴(kuò)展點(diǎn)，ApplicationContextAware有個方法setApplicationContext。

實現(xiàn)ApplicationContextAware接口，可以獲取到Spring的ApplicationContext上下文對象。ApplicationContext上下文繼承了BeanFactory, 因而可以從上下文對象獲取指定bean。如果該bean尚未創(chuàng)建，會觸發(fā)bean的創(chuàng)建流程，功能跟BeanFactoryAware相同。

示例

@Service
public class BeanFactoryUtils implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        this.applicationContext = applicationContext;
    }

    public static <T> T getBean(String beanName) {
        Objects.requireNonNull(beanName, "beanName不能為空!");
        return (T) applicationContext.getBean(beanName);
    }

    public static <T> T getBean(Class<T> requiredType) {
        Objects.requireNonNull(requiredType, "requiredType不能為空!");
        return (T) applicationContext.getBean(requiredType);
    }

    public <T> Collection<T> getBeanList(Class<T> requiredType) {
        return MapUtils.emptyIfNull(applicationContext.getBeansOfType(requiredType)).values();
    }
}