SpringBoot配置@Configuration注解和@bean注解

@Configuration //告诉SpringBoot这是一个配置类 == 配置文件
public class Config {
}

@Configuration //告诉SpringBoot这是一个配置类 == 配置文件
public class Config {
    @Bean   //给容器中添加组件。以方法名作为组件的id。返回类型就是组件类型。返回的值，就是组件在容器中的实例
    public Person person1(){
        return new Person("Mr.Yu",21,"male");
    }
    @Bean("customize")  //id值也可以指定
    public Person person2(){
        return new Person("小明",20,"male");
    }
}

@SpringBootApplication
public class MainApplication {
    public static void main(String[] args) {
        //1.返回我们IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
        //2.查看容器里面的组件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
    }
}

public static void main(String[] args) {
        //1.返回我们IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
        //2.查看容器里面的组件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        //单实例
        Person person1 = run.getBean("person1",Person.class);
        Person person2 = run.getBean("person1",Person.class);
        System.out.println("person1 == person2 :"+ (person1 == person2));
}

@SpringBootApplication
public class MainApplication {
    public static void main(String[] args) {
        //1.返回我们IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
        //2.查看容器里面的组件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        //配置类本身也是组件
        Config bean = run.getBean(Config.class);
        //com.ysw.boot.config.Config$$EnhancerBySprinGCGLIB$$4aa44992@381d7219
        System.out.println(bean);

    }
}

@SpringBootApplication
public class MainApplication {
    public static void main(String[] args) {
        //1.返回我们IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
        //2.查看容器里面的组件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        //配置类本身也是组件
        Config bean = run.getBean(Config.class);
        //获取到的本身就是代理对象
        //com.ysw.boot.config.Config$$EnhancerBySpringCGLIB$$4aa44992@381d7219
        System.out.println(bean);
        //如果我们直接调用person1方法，它是从IoC容器中拿还是直接new一个对象呢,
        //在new一个配置类出来的情况下，调用person1方法，它返回的是new出来的对象
        Config config = new Config();
        Person person3 = config.person1();
        Person person4 = config.person1();
        System.out.println("person3 == person4 :"+ (person3 == person4));
        //但是如果我们从容器中取得的配置类，无论再去掉用多少次person1方法，它始终返回的都是同一个单实例对象，也就是从IoC容器中拿的对象。
        //如果@Configuration(proxyBeanMethods = true)代理对象调用方法。SpringBoot总会检查这个组件是否在容器中有；
        //保持组件单实例
        Person person5 = bean.person1();
        Person person6 = bean.person1();
        System.out.println("person5 == person6 :"+ (person5 == person6));
    }
}