2.3使用java代码进行装配bean

@Configuration：表明这是个配置类，该类应该包含在spring应用上下文中。如果@Bean修饰的方法被                                      @Configuration修饰，那么方法是单例的。

@Bean：注解会告诉spring这个返回返回一个对象。该对象要注册为spring应用上下文中的bean，方法体中

包含了最终产生bean实例。默认情况下，bean的ID与带有@Bean注解的方法名是一样的。可以通过name属性重命名。

public interface MediaPlayer {
}

public class CDplayer implements MediaPlayer{

    private CompactDisc compactDisc;

    public CDplayer(CompactDisc compactDisc) {
        this.compactDisc = compactDisc;
    }

    public void play(){
        compactDisc.play();
    }
}

public interface CompactDisc {

    void play();
}

public class SgtPeppers implements CompactDisc{

    private String title = "Sgt. Pepper's Lonely Hearts Club Band";
    private String artist = "The Beatles";

    public void play() {
        System.out.println("Playing "+title+" by"+artist);
    }
}

@Configuration
@ComponentScan
public class CDPlayConfig {

    @Bean
    public CompactDisc sgtPeppers(){
        return new SgtPeppers();
    }

//    @Bean
//    public CDplayer cdplayer(){
//        System.out.println(sgtPeppers());
//        return new CDplayer(sgtPeppers());
//    }

    @Bean
    public CDplayer cdplayer(CompactDisc compactDisc){
        System.out.println(compactDisc);
        return new CDplayer(compactDisc);
    }
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayConfig.class)
public class CDPlayTest {

    @Autowired
    private CompactDisc cd;

    @Autowired
    private CDplayer cdplayer;

    @Test
    public void cdShouldNotBeNull(){
        cd.play();
    }


    @Test
    public void file(){
        File file = new File("");
    }

    @Test
    public void testJavaConfig(){
        System.out.println(cd);        //在CDPlayConfig中配置的@Bean是单例的，所以这个cd与config中
                                        CompactDisc是一样的

        System.out.println(cdplayer);
        cdplayer.play();
    }

}

来自为知笔记(Wiz)