spring探秘:通過BeanPostProcessor、@PostConstruct、InitializingBean在啟動前執行方法

springboot啟動前執行方法的3種方式：實現BeanPostProcessor接口、實現InitializingBean接口、使用@PostConstruct注解

示例：

第一種 實現BeanPostProcessor接口

@Configuration
public class Test3 implements BeanPostProcessor {

    @Autowired
    private Environment environment;

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        String property = environment.getProperty("aaa.bbb");
        System.out.println("test3"+property);
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

}

第二種 實現InitializingBean接口

@Configuration public class Test2 implements InitializingBean { @Autowired private Environment environment; @Override public void afterPropertiesSet() throws Exception { String property = environment.getProperty("aaa.bbb"); System.out.println("test2"+property); } }

第三種 使用@PostConstruct注解

@Configuration public class Test1 { @Autowired private Environment environment; @PostConstruct public void test(){ String property = environment.getProperty("aaa.bbb"); System.out.println("test1"+property); } }

 運行的優先級是：

啟動類前->BeanPostProcessor->@PostConstruct->InitializingBean

需注意：BeanPostProcessor的方式會讓實現類里的方法提前執行。BeanPostProcessor為每一個spring維護的對象調用前后做操作，實現了它我們當前類就會變成一個BeanPostProcessor對象，就可以像BeanPostProcessor一樣在容器加載最初的幾個階段被實例化，只要被實例化，PostConstruct注解的標注的方法就會立即執行。

 

參考： https://www.jianshu.com/p/1845fe64decd
https://www.jianshu.com/p/1417eefd2ab1