IOC装配Bean(注解方式)

时间:2024-01-18 21:21:08

Spring的注解装配Bean
  Spring2.5 引入使用注解去定义Bean
    @Component 描述Spring框架中Bean
  Spring的框架中提供了与@Component注解等效的三个注解
    @Repository 用于对DAO实现类进行标注
    @Service 用于对Service实现类进行标注
    @Controller 用于对Controller实现类进行标注
    ***** 三个注解为了后续版本进行增强的
  使用注解,那么applicationContext.xml配置文件要作出修改

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
      http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context.xsd">
  <context:annotation-config/>  <!--支持注解-->
  <context:component-scan base-package="cn.yzu.spring3"/>  <!--自动扫描-->
</beans>

Bean的属性注入
  普通属性

@Value(value="你好")
private String info;

  对象属性
    @Autowired:自动装配默认使用类型注入.
    @Qualifier("userDao"):按名称进行注入.

@Autowired
@Qualifier("userDao")
private UserDao userDao;

    等价于

@Resource(name="userDao")
private UserDao userDao;

Bean其他的属性的配置
  配置Bean初始化方法和销毁方法:init-method 和 destroy-method
    @PostConstruct 初始化
    @PreDestroy 销毁
  配置Bean的作用范围:@Scope("singleton")

@Service(value="userService")
@Scope("singleton")
public class UserService {
  @Value(value="你好")
  private String info;
  @Resource(name="userDao")
  private UserDao userDao;
  public void sayHello(){
    System.out.println("Hello Spring Annotation..."+info);
  }   @PostConstruct
  public void setup(){
    System.out.println("初始化...");
  }   @PreDestroy
  public void teardown(){
    System.out.println("销毁...");
  }
}

Spring3.0提供使用Java类定义Bean信息的方法(用的很少)

@Configuration
public class BeanConfig {
  @Bean(name="car")
  public Car showCar(){
    Car car = new Car();
    car.setName("长安");
    car.setPrice(40000d);
    return car;
  }   @Bean(name="product")
  public Product initProduct(){
    Product product = new Product();
    product.setName("空调");
    product.setPrice(3000d);
    return product;
  }
}
@Test
public void demo1(){
  ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
  Car car = (Car) applicationContext.getBean("car");
  Product product = (Product) applicationContext.getBean("product");
  System.out.println(car);
  System.out.println(product);
}

实际开发中使用XML还是注解?
  XML:有利于bean管理
  注解:注入属性的时候比较方便
  两种方式结合:一般使用XML注册Bean,使用注解进行属性的注入

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
      http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context.xsd">
  <!--使@Resource、@ PostConstruct、@ PreDestroy、@Autowired注解生效-->
  <context:annotation-config/>   <bean id="orderDao" class="cn.yzu.spring3.demo3.OrderDao"></bean>
  <bean id="customerService" class="cn.yzu.spring3.demo3.CustomerService"></bean>
</beans>
public class CustomerService {
  @Autowired
  @Qualifier("orderDao")
  private OrderDao orderDao;   @Override
  public String toString() {
    return "CustomerService [customerDao=" + customerDao + ", orderDao="+ orderDao + "]";
  }
}