Spring 中 ApplicationContextAware 的用法

当一个类实现了这个接口（ApplicationContextAware）之后，这个类就可以方便获得 ApplicationContext 中的所有bean。换句话说，就是这个类可以直接获取spring配置文件中，所有有引用到的bean对象

实现ApplicationContextAware方式

@Component
public class SpringContextUtils implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextService.applicationContext  = (SpringContextService.applicationContext == null) ?
                applicationContext : SpringContextService.applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name)
            throws BeansException {
        return (T) applicationContext.getBean(name);
    }

    public static <T> T getBean(Class<T> requiredType)
            throws BeansException {
        return applicationContext.getBean(requiredType);
    }

    public static <T> T getBean(String name, Class<T> requiredType)
            throws BeansException {
        return applicationContext.getBean(name, requiredType);
    }

    public static boolean containsBean(String name) {
        return applicationContext.containsBean(name);
    }

    public static boolean isSingleton(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.isSingleton(name);
    }

    public static Class getType(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.getType(name);
    }

    public static String[] getAliases(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.getAliases(name);
    }
}

在启动类中直接赋值

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        ApplicationContext applicationContext = SpringApplication.run(Application.class);
        SpringContextUtils.setApplicationContext(applicationContext);
    }

}

通过​​实现BeanFactoryAware接口​​实现