스프링 여러가지 의존성 주입(DI) 방법

public class A {
    B b;

    public void setB(B b) {
        this.b = b;
    }
}

<bean id="A" class="com.example.demo.BookService">
    <property name="bookRepository" ref="B"></property> --> 의존성 주입
</bean>

<bean id="B" class="com.example.demo.BookRepository"></bean>

혹은 ====================================================

@Bean
public class A{
    @Autowired --> 의존성 주입
    B b;
}

<context:component-scan base-package="com.example.demo"></context:component-scan>

혹은

@Configuration
public class AppConfig {

    @Bean
    public A a() {
        return new A();
    }

    @Bean
    public B b() {
        return new B();
    }
}

혹은

@Configuration
@ComponentScan(basePackages = "com.example.demo")
public class AppConfig {

}

혹은

@Configuration
@ComponentScan(basePackageClasses = AppConfig.class)
public class AppConfig {

}