@Value中#和$的用法

以下基于SpringBoot2.0+

@Value三种情况的用法。
$是去找外部配置的参数，将值赋过来
#是SpEL表达式，去寻找对应变量的内容
直接写字符串就是将字符串的值注入进去

$例子：

package com.example.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Value("${hx.name}")
    private String name;

    @GetMapping("getName")
    public String getName(){
        return this.name;
    }

}

配置文件：
application.properties

server.port=9090

hx.name = Chinese

上面那段代码中@Value("${hx.name}")会将配置文件中hx.name对应的值设置到name变量中：

#例子：

package com.example.demo;

import lombok.Data;
import org.springframework.stereotype.Component;

@Component
@Data
public class Another {
    private Integer id = 1;
    private String name = "xxx";
}

package com.example.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Value("#{another.name}")
    private String str;

    @GetMapping("getStr")
    public String getStr(){
        return this.str;
    }
}

上面代码中，将Another类的name属性注入到了str变量中：

例子

另外还有一种情况：

package com.example.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Value("hanxu")
    private String name;

    @GetMapping("getOth")
    public String getOth(){
        return this.name;
    }

}

直接将hanxu这个值注入到了name中：