SpringBoot中各类初始化方法顺序比较

r囧r小猫 2021-11-23 05:40 605阅读 0赞

在SpringBoot开发中想要在项目启动时执行一段代码，我们通常的做法有如下几种：  
1、实现接口ApplicationRunner

@Configuration
    public class TestApplicationRunner implements ApplicationRunner {
        @Override
        public void run(ApplicationArguments args) throws Exception {
            System.out.println("init ApplicationRunner");
        }
    }

2、实现接口CommandLineRunner

@Configuration
    public class TestCommandLineRunner implements CommandLineRunner {
    
        @Override
        public void run(String... args) throws Exception {
            System.out.println("init CommandLineRunner");
        }
    }

3、实现接口InitializingBean

@Configuration
    public class TestInitBean implements InitializingBean {
        @Override
        public void afterPropertiesSet() throws Exception {
            System.out.println("init InitializingBean");
        }
    }

4.实现接口ServletContextListener

@Configuration
    public class TestServletContextListener implements ServletContextListener {
    
        @Override
        public void contextInitialized(ServletContextEvent sce) {
            System.out.println("init ServletContextListener");
        }
    }

5、使用注解PostConstruct

@Configuration
    public class TestPostConstruct {
    
        @PostConstruct
        public void init(){
            System.out.println("init PostConstruct");
        }
    }

启动项目来看结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70]  
以上测试是基于springboot2.1.4.RELEASE进行的。  
还有一个接口BeanPostProcessor，经常用于在bean执行前后插入代码，例如

@Configuration
    public class TestBeanPostProcessor implements BeanPostProcessor {
    
        @Nullable
        @Override
        public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
            System.out.println("init bean:"+beanName + "before");
            return bean;
        }
    
        @Nullable
        @Override
        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
            System.out.println("init bean:"+beanName+" after");
            return bean;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70 1]  
虽然实现BeanPostProcessor后，执行会比实现ServletContextListener靠前很多，但是每个bean实例化都会执行，明显不适合用于做初始化。  
但是BeanPostProcessor和@PostConstruct组合使用会有意向不到的效果。

@Configuration
    public class TestBeanPostAndPostConstruct implements BeanPostProcessor {
    
        @PostConstruct
        public void init(){
            System.out.println("init BeanPostProcessor+PostConstruct");
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70 2]

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