BeanPostProcessor接口 和 InitializingBean接口

相同点：

1. 必须都被spring容器管理（对应注解或xml中配置bean），接口中的方法才会被使用生效；
2. 都是在bean实例化过程中调用接口对应的方法；

不同点：
InitializingBean
作用对象：只针对该接口的实现类bean；

BeanPostProcessor
作用对象：spring容器管理的所有bean；或可以在方法中自定义选择特定的bean处理业务逻辑

执行顺序：构造器->postProcessBeforeInitialization->@PostConstruct->afterPropertiesSet()->init-method属性->postProcessAfterInitialization

代码举例：

@Data
@ToString
public class Cart implements InitializingBean {

    public Cart() {
        System.out.println("构造器");
    }

    @FieldMapping("ID")
    private Integer id;

    @FieldMapping("DESC-lq")
    private String desc;

    @PostConstruct
    public void init() {
        System.out.println("init:" + this.getId());
    }

    private void initMethod() {
        System.out.println("initMethod:" + this.getId());
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("initializingBean:" + this.getId());
    }
}

@Configuration
public class CartConfiguration {

    @Bean(initMethod = "initMethod")
    public Cart cart() {
        return new Cart();
    }
}

@Component
public class BeanPostProcessorImpl implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization: " + beanName);
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization: " + beanName);
        return bean;
    }
}