@Component
public class Student {
    private String name;
    public Student() {
        System.out.println("stu被例項化!!!");
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
}

public class Teacher {
    @Resource
    private
 
 Student student;
    public Teacher() {
        System.out.println("Teacher被例項化！！！！" + student);
        student.setName("小明");
        System.out.println("老師正在教學生" + student.getName());
    }
}

會報NullPointer錯誤！！！

**在spring的文件裡面有說明，建構函式的呼叫要早於setter注入和欄位注入的，所以在呼叫建構函式的時候student還沒有賦值。