【Spring】IOC样例

一、注解方式

@Configuration

@ComponentScan("com.baeldung.constructordi")： perform a context scan for additional beans.

@Bean

@Configuration
@ComponentScan("com.baeldung.constructordi")
public class Config {

    @Bean
    public Engine engine() {
        return new Engine("v8", 5);
    }

    @Bean
    public Transmission transmission() {
        return new Transmission("sliding");
    }
}

其他Bean定义，通过上述@ComponentScan扫描得到

@Component
public class Car {

    @Autowired
    public Car(Engine engine, Transmission transmission) {
        this.engine = engine;
        this.transmission = transmission;
    }
}

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:

ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
Car car = context.getBean(Car.class);

二、XML配置

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

ApplicationContext context = new ClassPathXmlApplicationContext("baeldung.xml");
Car car = context.getBean(Car.class);