@Service
public class BookService {
    @Autowired
    private BookDao bookDao;

    public void print(){
        System.out.println(bookDao);
    }
}

applicationContext.getBean(BookDao.class);

applicationContext.getBean("bookDao");

package com.sunxiaping.dao;

import org.springframework.stereotype.Repository;

@Repository
public class BookDao {
}

package com.sunxiaping.serivice;

import com.sunxiaping.dao.BookDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class BookService {
    @Autowired
    private BookDao bookDao;

    public void print(){
        System.out.println(bookDao);
    }
}

package com.sunxiaping.controller;

import com.sunxiaping.serivice.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class BookController {
    @Autowired
    private BookService bookService;

    public void print(){
        System.out.println(bookService);
    }
}

package com.sunxiaping.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;


@ComponentScan(value = "com.sunxiaping")
@Configuration //告诉Spring这是一个配置类
public class SpringConfig {


}

package com.sunxiaping.test;


import com.sunxiaping.config.SpringConfig;
import com.sunxiaping.controller.BookController;
import com.sunxiaping.serivice.BookService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class SpringTest {

    @Test
    public void test() {
        ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);

        BookController bookController = context.getBean(BookController.class);

        bookController.print();

        BookService bookService = context.getBean(BookService.class);

        bookService.print();

    }

}