SPRING IN ACTION 第4版笔记-第二章-002-@ComponentScan、@Autowired的用法

一、@ComponentScan

1.

@Configuration    //说明此类是配置文件
@ComponentScan //开启扫描，会扫描当前类的包及其子包
public class CDPlayerConfig {
}

2.

@ComponentScan(basePackages={"soundsystem", "video"})//扫描多个包
public class CDPlayerConfig {
}

3.

@ComponentScan(basePackageClasses={CDPlayer.class,AAA.class})//指定要扫描的类
public class CDPlayerConfig {
}

二、@Autowired

1.可以在构造方法中用

@Component
public class CDPlayer implements MediaPlayer {
  private CompactDisc cd;

  @Autowired
  //@Inject
  public CDPlayer(CompactDisc cd) {
    this.cd = cd;
  }

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

}

2.在set方法中

@Autowired
public void setCompactDisc(CompactDisc cd) {
this.cd = cd;
}

3.在一般的方法中

@Autowired
public void insertDisc(CompactDisc cd) {
this.cd = cd;
}

4.如果依赖不是必需的，可设置属性

@Autowired(required=false)
public CDPlayer(CompactDisc cd) {
this.cd = cd;
}

5.可用@Inject替代

 package soundsystem;
 import javax.inject.Inject;
 import javax.inject.Named;
 @Named
 public class CDPlayer {
 ...
 @Inject
 public CDPlayer(CompactDisc cd) {
 this.cd = cd;
 }
 ...
 }