@Configuration
@ComponentScan("com.baeldung.constructordi")： perform a context scan for additional beans.
@Bean
1 @Configuration 2 @ComponentScan("com.baeldung.constructordi") 3 public class Config { 4 5 @Bean 6 public Engine engine() { 7 return new Engine("v8", 5); 8 } 9 10 @Bean 11 public Transmission transmission() { 12 return new Transmission("sliding"); 13 } 14 }
其他Bean定义，通过上述@ComponentScan扫描得到
1 @Component 2 public class Car { 3 4 @Autowired 5 public Car(Engine engine, Transmission transmission) { 6 this.engine = engine; 7 this.transmission = transmission; 8 } 9 }
使用：AnnotationConfigApplicationContext
Spring will encounter our Car class while doing a package scan, and will initialize its instance by calling the @Autowired annotated constructor.
By calling the @Bean annotated methods of the Config class, we will obtain instances of Engine and Transmission. Finally, we need to bootstrap an ApplicationContext using our POJO configuration:
1 ApplicationContext context = new AnnotationConfigApplicationContext(Config.class); 2 Car car = context.getBean(Car.class);
定义构造器的XML Bean配置
<bean id="toyota" class="com.baeldung.constructordi.domain.Car"> <constructor-arg index="0" ref="engine"/> <constructor-arg index="1" ref="transmission"/> </bean> <bean id="engine" class="com.baeldung.constructordi.domain.Engine"> <constructor-arg index="0" value="v4"/> <constructor-arg index="1" value="2"/> </bean> <bean id="transmission" class="com.baeldung.constructordi.domain.Transmission"> <constructor-arg value="sliding"/> </bean>
使用ClassPathXmlApplicationContext
1 ApplicationContext context = new ClassPathXmlApplicationContext("baeldung.xml"); 2 Car car = context.getBean(Car.class);
原文：https://www.cnblogs.com/clarino/p/15227393.html