本篇文章继续上篇文章讲解Ioc基础，这篇文章主要介绍零配置实现ioc，现在相信大家项目中也基本都是没有了xml配置文件。废话不多说。一起学习

代码示例

• BookDao.java

package com.kevin.spring.demo1.dao;

/**
 * 图书数据访问接口
 */
public interface BookDao {

    /**
     * 添加图书
     *
     * @param bookName
     * @return
     */
    String addBook(String bookName);
}

• BookDaoImpl.java

/**
 * 接口实现类
 */
@Repository
public class BookDaoImpl implements BookDao {
    /**
     * 添加图书接口
     *
     * @param bookName
     * @return
     */
    public String addBook(String bookName) {
        return "添加图书《" + bookName + "》成功";
    }
}

• BookService.java

@Service
public class BookService {
    @Resource
    BookDaoImpl bookDao;

    public void storeBook(String bookName){
        String result = bookDao.addBook(bookName);
        System.out.println(result);
    }

}

• User.java

package com.kevin.spring.demo1.entity;

import org.springframework.stereotype.Component;

@Component
public class User {

    public User() {
        System.out.println("创建User对象");
    }

    public User(String msg) {
        System.out.println("创建User对象" + msg);
    }

    public void show() {
        System.out.println("一个学生对象！");
    }
}

• ApplicationConfig.java

package com.kevin.spring.demo1.config;

import com.kevin.spring.demo1.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = "com.kevin.spring.demo1")
public class ApplicationConfig {

    @Bean
    public User getUser(){
        return new User("成功");
    }
}

测试类

    @org.junit.Test
    public void testBook(){
        ApplicationContext ctx = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        BookService bookService = ctx.getBean(BookService.class);
        bookService.storeBook("周杰伦");
        User user = ctx.getBean("getUser",User.class);
        user.show();
    }

运行结果

创建User对象
创建User对象成功
添加图书《周杰伦》成功
一个学生对象！

@Configuration

@Configuration 相当于配置文件中的<beans/>

@ComponentScan

@ComponentScan相当于配置文件中的context:component-scan

@Bean

@Bean相当于<bean/>，只能注解在方法和注解上，一般在方法上使用
方法名相当于id

这里注意上面获取user时用的是getUser,因为方法名相当于id

@Value获取properties配置

• 新建一个dev.properties文件

boy.name = kevin
boy.age = 20

• BoyUtil.java

package com.kevin.spring.demo1.util;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource("classpath:dev.properties")
public class BoyUtil {

    @Value("${boy.name}")
    private String name;
    @Value("${boy.age}")
    private String age;

    @Override
    public String toString() {
        return "BoyUtil{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
    //get和set方法省略
}

测试

    @org.junit.Test
    public void testBoyUtil(){
        ApplicationContext ctx = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        BoyUtil boyUtil = ctx.getBean(BoyUtil.class);
        System.out.println(boyUtil);
    }

输出结果

创建User对象
创建User对象成功
BoyUtil{name='kevin', age='20'}

好了，springIoc基础就暂时告一段落。玩的开心
代码：https://github.com/runzhenghengbin/spring-study
参考：https://www.cnblogs.com/best/p/5727935.html#_label3