Spring中的Aware

• Spring框架中提供了許多實現了Aware介面的類，這些類主要是為了輔助Spring訪問容器中的資料，比如BeanNameAware，這個類能夠在Spring容器載入的過程中將Bean的名字（id）賦值給變數。

ApplicationContextAware

實現該類可以獲取到ApplicationContext，通過ApplicationContext就可以獲取到Bean

@Component
public class SpringUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        if(SpringUtil.applicationContext == null){
            SpringUtil.applicationContext = applicationContext;
        }
    }

    public static ApplicationContext getApplicationContext(){
        return applicationContext;
    }

    public static Object getBean(String name){
        return getApplicationContext().getBean(name);
    }

    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    public static <T> T getBean(String name,Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }

}
 

EmbeddedValueResolverAware

通過實現該類就可以獲取到spring核心配置檔案中的配置值（application.yml,application.properties）。

但是需要通過${key}獲取

/**
 * 非spring容器管理的類可以通過此類獲取配置值
 */
@Component
public class PropertiesUtil implements EmbeddedValueResolverAware {

    private static StringValueResolver resolver;

    @Override
    public void setEmbeddedValueResolver(StringValueResolver resolver) {
        PropertiesUtil.resolver = resolver;
    }

    public static String getPropertiesValue(String key){
        return resolver.resolveStringValue(key);
    }
}
 

舉例：

String name = PropertiesUtil.getPropertiesValue("${spring.application.name}")