Spring bean初始化方法的几种写法

野性酷女 2021-09-24 16:54 289阅读 0赞

项目路径：[https://gitee.com/wuhan1/spring-parent.git][https_gitee.com_wuhan1_spring-parent.git] 下的spring-06,

工程截图  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RoajE5OTE4MQ_size_16_color_FFFFFF_t_70][]  
1.指明initMethod和destroyMethod，新建Stu类，

public class Stu {
    
        public void myInit(){
            System.out.println("学生初始化");
        }
    
        public void myDestroy(){
            System.out.println("学生销毁");
        }
    }

把Stu注入当容器中，并增加初始化myInit和销毁方法myDestroy

@Configuration
    @ComponentScan("com.xqc")//扫描的包
    public class SpringConfig {
    
        @Bean(initMethod = "myInit",destroyMethod = "myDestroy")
        public Stu stu(){
            return new Stu();
        }
    }

启动和关闭容器，查看结果

public class SpringTest {
        public static void main(String[] args) {
            AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
            context.close();//关闭
    
        }
    }

![20200919174335695.png][]

2.@PostConstruct(初始化)+@PreDestroy(销毁方法)，JSR250提供的.。新建Stu2类，并用@PostConstruct和@PreDestroy注解表明初始化和销毁方法

public class Stu2 {
    
        /**
         * 初始化方法
         */
        @PostConstruct
        public void myInit(){
            System.out.println("学生初始化2");
        }
    
        /**
         * 销毁方法
         */
        @PreDestroy
        public void myDestroy(){
            System.out.println("学生销毁2");
        }
    }

在Config类中

@Bean
        public Stu2 stu2(){
            return new Stu2();
        }

打印结果  
![20200919175112127.png][]

3.实现InitializingBean和DisposableBean接口，实现接口对应的方法，新建学生类Stu3

public class Stu3 implements InitializingBean, DisposableBean {
    
        @Override
        public void afterPropertiesSet() throws Exception {
            System.out.println("学生初始化3");
        }
    
        @Override
        public void destroy() throws Exception {
            System.out.println("学生销毁3");
        }
    }

@Bean
        public Stu3 stu3(){
            return new Stu3();
        }

执行结果  
![20200919180205214.png][]

4.实现BeanPostProcessor接口,此接口会拦截所有的Bean,可以改bean的返回类型，新建MyBeanPostProcessor

@Component
    public class MyBeanPostProcessor implements BeanPostProcessor {
    
        /**
         * 拦截所有的bean
         */
        @Override
        public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    //        if(bean instanceof Stu4){
            System.out.println("MyBeanPostProcessor初始化4");
    //        }MyBeanPostProcessor
            return bean;
        }
    
        @Override
        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    //        if(bean instanceof Stu4){
            System.out.println("MyBeanPostProcessor销毁4");
    //        }
            System.out.println(bean);
            return bean;
        }
    }

[https_gitee.com_wuhan1_spring-parent.git]: https://gitee.com/wuhan1/spring-parent.git
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RoajE5OTE4MQ_size_16_color_FFFFFF_t_70]: /images/20210923/8de0846bd6764d6386cde27196a3b548.png
[20200919174335695.png]: /images/20210923/6a240fd103674151a32f1a65bc9dcc89.png
[20200919175112127.png]: /images/20210923/8617058787664c1690f2832cbf288204.png
[20200919180205214.png]: /images/20210923/6219d246d9664a5fb525091cf22a8482.png