@value与@ConfigurationProperties注解

时间:2022-05-22 qq_29914229 人气:0

@value注解和@ConfigurationProperties注解

@value读取默认配置

yml文件内容如下（装了STS插件以后即可直接使用，改后缀就行了）

user:
  username: xiongda
  sex: man
  age: 20
school:
  name: xtu
  location: hunan

备注：一定要注意之间要留空格，发现颜色变绿色了才是正确的格式，这个坑我刚踩

package com.example.demo.service.impl; 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service; 
import com.example.demo.service.ReadConfigService; 
@Service
public class ReadConfigServiceImpl implements ReadConfigService {    
    @Value(value="${user.username}")
    private String username;
    
    @Value(value="${user.sex}")
    private String sex;
    
    @Value(value="${user.age}")
    private String age;
    
    @Value(value="${school.name}")
    private String name;
    
    @Value(value="${school.location}")
    private String location;
    
    @Override
    public String getUserMessage() {
        return "user ="+username+" sex ="+sex+" age="+age;
    }
 
    @Override
    public String getAuthorMessage() {
        return "schoolname="+name+"location="+location;
    }    
}

@ConfigurationProperties读取默认配置

package com.example.demo.config; 
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component; 
@Component
@ConfigurationProperties(prefix="user")
public class HelloConfig {
    private String username;    
    private String sex;    
    private String age; 
    public String getUsername() {
        return username;
    }
 
    public void setUsername(String username) {
        this.username = username;
    }
 
    public String getSex() {
        return sex;
    }
 
    public void setSex(String sex) {
        this.sex = sex;
    }
 
    public String getAge() {
        return age;
    }
 
    public void setAge(String age) {
        this.age = age;
    }    
}

调用的controller层

package com.example.demo.web; 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController; 
import com.example.demo.config.HelloConfig;
import com.example.demo.service.ReadConfigService;
 
@RestController
@RequestMapping("hello")
public class HelloController {
    
    @Autowired
    ReadConfigService readConfigService;
    
    @Autowired
    HelloConfig helloConfig;
    
    @RequestMapping("/user")
    public String say() {
       return "username "+helloConfig.getUsername()+" sex "+helloConfig.getSex()+" age "+helloConfig.getAge();
    }
    
    @RequestMapping("/school")
    public String school() {
       return readConfigService.getAuthorMessage();
    }
}

@ConfigurationProperties和@Value使用上的一点区别

@ConfigurationProperties和@Value的一个共同点就是从配置文件中读取配置项。

发现有一点区别，我项目配置中并没有配置hello.msg ，当使用第一段代码时，启动后读取到msg为null，而第二段代码则会抛出异常。

第二段代码有个好处，就是防止我们配置项遗漏，当遗漏时，启动程序肯定出错，这样避免了一些因为遗漏配置项导致的BUG.

第一段代码

import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("hello")
public class HelloProperties {
    private String msg;
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
}

第二段代码

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class Hello2Properties {
    @Value("${hello.msg}")
    private String msg;
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。

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