IoC容器的单例(singleton)多例(prototype)问题，多例对象的生命周期问题

IoC容器可以自动管理Bean的初始化和销毁方法，用到的就是@PostConstruct(构造后)和@PreDestory(销毁前)注解.

@Service
//@Scope("singleton")//默认单例模式
public class AlphaService {
    public AlphaService(){
        System.out.println("实例化AlphaService");
    }
    @PostConstruct
    public void init(){
        System.out.println("初始化AlphaService");
    }
    @PreDestroy
    public void destory(){
        System.out.println("销毁AlphaService");
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = CommunityApplication.class)
//这个是为了在test中用main的环境，因为Spring容器的注入有两个条件：
//@SpringBootApplication所在包及其子包内，相应的注解这里就是@Service
public class CommunityApplicationTests implements ApplicationContextAware {
    public ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
        //上面就是构建IoCr
    @Test
    public void testManagementBean() {
        AlphaService alphaService = applicationContext.getBean(AlphaService.class);
        System.out.println(alphaService);
        alphaService = applicationContext.getBean(AlphaService.class);
        System.out.println(alphaService);
    }
 }

2019-12-22 10:30:10.211  INFO 35996 --- [           main] c.n.community.CommunityApplicationTests  : Starting CommunityApplicationTests on wan-HP with PID 35996 (started by wan in E:\牛客高薪项目课\所有素材和源码\第一章素材和源码\源码\community)
2019-12-22 10:30:10.212  INFO 35996 --- [           main] c.n.community.CommunityApplicationTests  : No active profile set, falling back to default profiles: default
实例化AlphaService
初始化AlphaSevice
2019-12-22 10:30:11.906  INFO 35996 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-12-22 10:30:12.094  WARN 35996 --- [           main] ion$DefaultTemplateResolverConfiguration : Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
2019-12-22 10:30:12.312  INFO 35996 --- [           main] c.n.community.CommunityApplicationTests  : Started CommunityApplicationTests in 2.451 seconds (JVM running for 3.52)
com.nowcoder.community.service.AlphaService@de81be1
com.nowcoder.community.service.AlphaService@de81be1
2019-12-22 10:30:12.833  INFO 35996 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'
销毁AlphaService

Process finished with exit code 0

这里我们可以看到两次的getBean我们只会实例化一次，即单例。如果我们希望每次getBean都实例化，那么我们就需要切换为多例模式(prototype)

@Service
@Scope("prototype")
public class AlphaService {
    public AlphaService(){
        System.out.println("实例化AlphaService");
    }
    @PostConstruct
    public void init(){
        System.out.println("初始化AlphaSevice");
    }
    @PreDestroy
    public void destory(){
        System.out.println("销毁AlphaService");
    }
}

2019-12-22 11:01:16.246  WARN 37288 --- [           main] ion$DefaultTemplateResolverConfiguration : Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
2019-12-22 11:01:16.505  INFO 37288 --- [           main] c.n.community.CommunityApplicationTests  : Started CommunityApplicationTests in 2.613 seconds (JVM running for 3.686)
实例化AlphaService
初始化AlphaSevice
com.nowcoder.community.service.AlphaService@568750b7
实例化AlphaService
初始化AlphaSevice
com.nowcoder.community.service.AlphaService@3e28fee1
2019-12-22 11:01:17.058  INFO 37288 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

Process finished with exit code 0

这里我们发现他实例化了两次， 但是我们发现并没有出现销毁方法，这是由于多例对象Spring容器只负责创建而不负责回收，因此不会调用销毁方法。

下面的链接中博主详细测试了多例方法的生命周期：
spring-多例对象prototype-生命周期方法问题