spring探秘:通过BeanPostProcessor、@PostConstruct、InitializingBean在启动前执行方法
spring探秘:通过BeanPostProcessor、@PostConstruct、InitializingBean在启动前执行方法
springboot启动前执行方法的3种方式：实现BeanPostProcessor接口、实现InitializingBean接口、使用@PostConstruct注解
示例：
第一种 实现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;
}
}
第二种 实现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);
}
}第三种 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);
}
}运行的优先级是：
启动类前->BeanPostProcessor->@PostConstruct->InitializingBean
需注意：BeanPostProcessor的方式会让实现类里的方法提前执行。BeanPostProcessor为每一个spring维护的对象调用前后做操作，实现了它我们当前类就会变成一个BeanPostProcessor对象，就可以像BeanPostProcessor一样在容器加载最初的几个阶段被实例化，只要被实例化，PostConstruct注解的标注的方法就会立即执行。
