Spring的Aware接口实现及执行顺序详解
刨红薯的小羊竿尔 人气:0一、实现了Aware的接口
Spring中有很多继承于aware中的接口,这些接口到底是做什么用到的,下面我们就一起来看看吧。
Aware 接口用于注入一些与容器相关信息,例如:
EnvironmentAware
:实现EnvironmentAware接口重写setEnvironment方法后,可以获得配置文件属性值
BeanClassLoaderAware
:注入加载当前 bean 的 ClassLoader
BeanNameAware
: 注入当前 bean 对应 beanName
BeanFactoryAware
: 注入 当前BeanFactory容器 的引用
ApplicationContextAware
: 获取容器本身ApplicationContext对象,可以在bean中得到bean所在的应用上下文
EmbeddedValueResolverAware
:获取properties文件单个属性值,一般使用@Value
属性值;EmbeddedValueResolverAware是另一种基于Spring解析获取 properties
文件单个属性值的方式
ApplicationEventPublisherAware
:事件发布器的接口,使用这个接口,我们自己的bean就拥有了发布事件的能力。
ResourceLoaderAware
:获取ResourceLoader实例,获取资源加载器读取资源文件
二、为什么要使用 Aware 接口
Aware接口是回调,监听器和观察者设计模式的混合,一般指具备由Spring 容器通过Aware回调方法通知的特定的bean对象,简单来说就是可以通过实现该接口拿到Spring容器内部的一些资源。实际的回调方法由各个子接口确定,通常应仅包含一个接受单个参数、返回 void 的方法;但是一般情况下,Spring不建议使用该接口,因为使用这种方式会将业务代码与Spring 耦合,有所违背IOC 原则。
1、BeanNameAware
public class MyBeanName implements BeanNameAware { @Override public void setBeanName(String beanName) { System.out.println(beanName); } }
2、BeanFactoryAware
public class MyBeanFactory implements BeanFactoryAware { private BeanFactory beanFactory; @Override public void setBeanFactory(BeanFactory beanFactory) throws BeansException { this.beanFactory = beanFactory; } public void getMyBeanName() { MyBeanName myBeanName = beanFactory.getBean(MyBeanName.class); System.out.println(beanFactory.isSingleton("myCustomBeanName")); } }
3、EnvironmentAware
@Configuration public class MyBatisConfig implements EnvironmentAware { private static Environment environment; @Override public void setEnvironment(Environment environment) { this.environment = environment; } @Bean public DataSource druidDataSource() throws Exception { Properties props = new Properties(); props.put("driverClassName", environment.getProperty("datasource.driverClassName")); props.put("url", environment.getProperty("datasource.url")); props.put("username", environment.getProperty("datasource.username")); props.put("password", environment.getProperty("datasource.password")); return DruidDataSourceFactory.createDataSource(props); } }
4、EmbeddedValueResolverAware
@Component public class PropertiesUtil implements EmbeddedValueResolverAware { private StringValueResolver resolver; @Override public void setEmbeddedValueResolver(StringValueResolver resolver) { this.resolver = resolver; } /** * 获取属性,直接传入属性名称即可 * @param key * @return */ public String getPropertiesValue(String key) { StringBuilder name = new StringBuilder("${").append(key).append("}"); return resolver.resolveStringValue(name); } }
public class MyBean implements BeanNameAware, ApplicationContextAware, InitializingBean { private static final Logger log = LoggerFactory.getLogger(MyBean.class); @Override public void setBeanName(String name) { log.debug("当前bean " + this + " 名字叫:" + name); } @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { log.debug("当前bean " + this + " 容器是:" + applicationContext); } @Override public void afterPropertiesSet() throws Exception { log.debug("当前bean " + this + " 初始化"); } }
三、Aware接口执行顺序
定义类SimpleAware实现了部分Aware的接口的自定义bean,经过程序运行测试其执行顺序如下:
@Component public class SimpleAware implements ApplicationContextAware, ApplicationEventPublisherAware, BeanClassLoaderAware, BeanFactoryAware, BeanNameAware, ResourceLoaderAware { @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { System.out.println("ApplicationContextAware 回调"); } @Override public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) { System.out.println("ApplicationEventPublisherAware 回调"); } @Override public void setBeanClassLoader(ClassLoader classLoader) { System.out.println("BeanClassLoaderAware 回调"); } @Override public void setBeanFactory(BeanFactory beanFactory) throws BeansException { System.out.println("BeanFactoryAware 回调"); } @Override public void setBeanName(String name) { System.out.println("BeanNameAware 回调"); } @Override public void setResourceLoader(ResourceLoader resourceLoader) { System.out.println("ResourceLoaderAware 回调"); } }
按照以下顺序执行:
BeanNameAware-->BeanClassLoaderAware-->BeanFactoryAware-->ResourceLoaderAware-->ApplicationEventPublisherAware-->ApplicationContextAware
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