1.以Hello类为例改为用注解方式

Hello类，采用@Component注解：

import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/2/28.
  * @Component用于类级别注解，标注本类为一个可被Spring容器托管的
        */
    @Component
      public class Hello {
         public String gethello(){
            return "Hello World";
 }
}

HelloApp类，则采用@ComponentScan来注解：

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Component;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Created by Administrator on 2019/2/28.
 * @Component
 */

@Component
public class HelloApp {
    public static void main(String[] args) {
        //1.通过注解创建上下文对象
        ApplicationContext context = new AnnotationConfigApplicationContext(HelloApp.class);
        //2.读取bean
        Hello hello = context.getBean(Hello.class);
        //3.运行
        System.out.println(hello.gethello());
    }
}

运行结果为：

运行结果

2.以Student和Phone为例

首先学会如何使用Lombok插件
按照下面步骤安装并记得需要重启IDEA

File-Settings...

找到Plugins

接下来添加依赖：

<dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.16.18</version>
      <scope>provided</scope>
  </dependency>

Phone类

import lombok.Data;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/2/28.
 * 采用注解和Lombok开发的Phone类
 */
@Component
@Data
public class Phone {
    @Value("华为")
    private String brand;

    @Value("1888.88")
    private double price;
}

Student类

import lombok.Data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/2/28.
 */
@Component
@Data
public class Student {
    @Value("Sunming")
    private String name;

    @Value("21")
    private int age;

    //注入@Autowired注入
    @Autowired
    private Phone phone;
}

StudentApp类：

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;

/**
 * Created by Administrator on 2019/2/28.
 */
@ComponentScan
public class StudentApp {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(StudentApp.class);
        Student student=context.getBean(Student.class);
        System.out.println(student);
    }
}