聊聊@value注解和@ConfigurationProperties注解的使用_Java教程

@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）

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									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

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									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

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									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

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									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

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									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

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									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;

									    }

									}