《Spring in action》之装配Bean

创建应用对象之间协作关系的行为通常称为装配，这也是依赖注入的本质。Spring装配Bean的三种主要机制：1.在XML中进行显示配置2.在java中进行显示配置3.隐式的bean发现机制和自动装配1.自动化装配  1.组件扫描：spring会自动发现上下文中创建的Bean  2.自动装配：Spring自动满足bean之间的依赖组件扫描

public interface Phone {
    void speak();
}

@Component定义组件，@Component(“apple”)可以指定组件id

@Component
public class Apple implements Phone{
    @Override
    public void speak() {
        System.out.println("apple speak");
    }
}

 创建配置类:注解@ComponentScan启用了组件扫描，basePackages扫描指定单个包，多个包(basePackages ={“”,””})

@Configuration
//@ComponentScan(basePackages = "com.spring.ioc.autowiring")
@ComponentScan(basePackages = {"com.spring.ioc.autowiring","com.spring.di"})
public class PhoneConfig {
}

 这里也可以不用这个类配置@ComponentScan，可用xml配置

<!-- 启用组件扫描-->
<context:component-scan base-package="com.spring.ioc.autowiring"/>

测试:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = PhoneConfig.class)
public class PhoneTest {
    @Autowired
    private Phone phone;
    @Test
    public void checkPhone(){
        phone.speak();
        Assert.assertNotNull(phone);
    }
}

 自动装配

@Autowired

public class Xiaoming {
    private Phone phone;
    //这里不管是构造方法、set方法、普通方法@Autowired都能自动装配
    @Autowired
    public Xiaoming(Phone phone) {
        this.phone = phone;
    }    public void speak(){
        phone.speak();
    }
}

 2.通过java代码装配bean代码如下：

public class XiaoMi implements Phone{
    @Override
    public void speak() {
        System.out.println("小米。。。。。。");
    }
}

创建配置类:

@Configuration
public class JavaConfig {    @Bean
    public Phone getPhone(){
        return new XiaoMi();
    }
}　　

junit测试：

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = JavaConfig.class)
public class JavaConfigTest {
    @Autowired
    private Phone phone;
    @Test
    public void checkPhone(){
        phone.speak();
        Assert.assertNotNull(phone);
    }
}

也可以通过如下main测试

public static void main(String[] args) {
    //加载java配置类获取Spring应用上下文
    ApplicationContext ac = new AnnotationConfigApplicationContext(JavaConfig.class);
    XiaoMi xiaoMi= ac.getBean(XiaoMi.class);
    xiaoMi.speak();
}

3.在XML中进行显示配置声明bean用<bean id=”xxx” class=”xxx”>标签