@Autowired 作用范围

@Component
public class Student{
    
    private Book book;

    public Book getBook() {
        return book;
    }
    
    //@Autowired 标注在方法上, Spring 容器在创建当前对象的时候,就会调用该方法,完成赋值
    //方法使用的参数,自定义类型的的值从容器中获取
    @Autowired
    public void setBook(Book book) {
        this.book = book;
    }
}

@Component
public class Student{
    
    private Book book;
    
    //容器启动会默认调用无参构造器,再进行初始化赋值等操作
    //@Autowired 加载构造方法上,容器启动的时候,就会调用该构造方法创建对象。构造器要用的参数,都是从容器中获取
    @Autowired
    public Student(Book book) {
        super();
        this.book = book;
    }

    public Book getBook() {
        return book;
    }
    
    public void setBook(Book book) {
        this.book = book;
    }
}

@Component
public class Student{
    
    private Book book;
    
    //容器启动会默认调用无参构造器,再进行初始化赋值等操作
    //@Autowired 加载构造方法上,容器启动的时候,就会调用该构造方法创建对象。构造器要用的参数,都是从容器中获取
    public Student(@Autowired Book book) {
        super();
        this.book = book;
    }

    public Book getBook() {
        return book;
    }
    
    public void setBook(Book book) {
        this.book = book;
    }
}

@Autowired
private Student student;