Major difference: if @ComponentScan, manually configure(use another class with @ComponentScan to tell Spring IoC container where beans are to inject resources into). If @Autowired, no such class and manually injection are needed.

当Spring生成所有的Bean后，发现这个注解，就会在现在有的Bean中查找，找到对应的bean，将class定义好的bean注入到这个注解下的bean中，完成依赖注入。

@ComponentScan

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package com.chap10.annotation.service;

import com.chap10.annotation.pojo.Role;

public interface RoleService {
    public void printRoleInfo(Role role);
}
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package com.chap10.annotation.service.impl;

import com.chap10.annotation.pojo.Role;
import com.chap10.annotation.service.RoleService;
import org.springframework.stereotype.Component;

@Component
public class RoleServiceImpl implements RoleService {
    @Override
    public void printRoleInfo(Role role) {
        System.out.println("id = " + role.getId());
        System.out.println("roleName = " + role.getRoleName());
        System.out.println("note= " + role.getNote());
    }
}
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package com.chap10.main;

import com.chap10.annotation.config.ApplicationConfig;
import com.chap10.annotation.pojo.Role;
import com.chap10.annotation.service.RoleService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class MainComponentScan {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(ApplicationConfig.class);

        Role role = context.getBean(Role.class);
        RoleService roleService = context.getBean(RoleService.class);
        roleService.printRoleInfo(role);
        context.close();
    }
}

@Autowired

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package com.chap10.annotation.service;

public interface RoleService2 {
    public void printRoleInfo();
}
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package com.chap10.annotation.service.impl;

import com.chap10.annotation.pojo.Role;
import com.chap10.annotation.service.RoleService2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan
public class RoleServiceImpl2 implements RoleService2 {

    @Autowired
    private Role role = null;

    public Role getRole() {
        return role;
    }

    public void setRole(Role role) {
        this.role = role;
    }

    @Override
    public void printRoleInfo() {
        System.out.println("id = " + role.getId());
        System.out.println("roleName = " + role.getRoleName());
        System.out.println("note= " + role.getNote());
    }
}
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package com.chap10.main;

import com.chap10.annotation.config.ApplicationConfig;
import com.chap10.annotation.service.RoleService2;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class MainAutowired {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(ApplicationConfig.class);

        RoleService2 roleService2 = context.getBean(RoleService2.class);
        roleService2.printRoleInfo();
        context.close();
    }
}

Using @Autowired is recommended.