@Autowired，@Service，@Resource，@Altowired+@Qualifier，@Configuration，@Value

运行函数：

@Autowired在这里获取bean

package com.exa.de.controller;

import com.exa.de.entity.User;
import com.exa.de.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

/**
 * @RestController注解，相当于@Controller+@ResponseBody两个注解的结合
 * 返回json数据不需要在方法前面加@ResponseBody注解了，但使用@RestController这个注解，就不能返回jsp,html页面，视图解析器无法解析jsp,html页面
 */
@RestController
@RequestMapping("action")
public class UserActionlController {

    @Autowired
    private UserService userService;
    @GetMapping//url://http://localhost:8080/action
    public  User get(){
        return userService.get();
    }


    @GetMapping("{id}")//url://http://localhost:8080/action/id(一个int类型)
    @CrossOrigin//跨域处理
    public User getById(@PathVariable("id")int id){

        return userService.getById(id);
    }


}

2.实现类，

@Service注册bean，在实现类中不是接口

package com.exa.de.service.impl;

import com.exa.de.entity.User;
import com.exa.de.service.UserService;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.PathVariable;
@Service
public class UserServiceImpl implements UserService {//implements继承：实现类UserServiceImpl 继承implements 接口UserService

    public User get() {
        User user = new User(1, "lin", "男", 25);
        System.out.println("get user =" + user);
        return user;
    }
    public User getById(@PathVariable("id")int id){
        User user = new User(id,"huang","nv",18);
        System.out.println("getById user"+user);
        return user;
    }
}

3.接口

package com.exa.de.service;

import com.exa.de.entity.User;

public interface UserService {
    public User get();
    public User getById(int id);
}

结果

 @Service和@Component都是获取bean，用途差别不大

@Resource和@Altowired+@Qualifier
如果接口实现只有一个，那么用@Autowired就可以了，也不需要指定名字,

如果接口有多个实现，那么，用@Resource，并指定name(建议)
或者使用导@Altowired+@Qualifier，@Qualifier的value

    @Autowired
    @Qualifier("autowiredServiceImpl")//实现类的name首字母自动小写
    private UserService userService;

    @Resource(name = "userServiceImpl")
    private UserService userService1;

@Configuration人工写一个bean

@Configuration
public class MyBeans {
    @Bean
    public UserService autowired(){//假设bean 'autowired'被注册，就禁止重写，重命名一个bean
        return new AutowiredServiceImpl();
    }
    @Bean
    public UserService user(){
        return new UserServiceImpl();
    }
}

@Value从配置文件中取参数

 application.properties：

view.page=view;
local.username =guang;//名字，路径可以随便username也可以

local.userage=123456;

package com.exa.de.controller;

import com.exa.de.entity.User;
import com.exa.de.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;


@RestController
@RequestMapping("action")
public class UserActionlController {
    @Value("${view.page}")
    private String page;

    @Value("${local.username}")
    private String username;

    @Value("${local.userage}")
    private String userage;

    @GetMapping("val")
    public String getValue(){
        System.out.println();

        return "value{page="+page+",username="+username+"+,userage="+userage+"}";
    }


}