CODEWITHSUNDEEP
javaspring-mvcspring-bootannotations
lanyyyy
lanyyyy

Reputation: 11

How java @Value works?

I used java @Value like this, it works fine, and the variable "baiduurl" can be resolved correctly:

package com.lanyyyy.springdemo.controllers;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.lanyyyy.springdemo.service.*;
@RestController
public class GetURL {
    @Value("${baiduurl}")
    public String baiduurl;

    @RequestMapping(path="/getbaidu", method=RequestMethod.GET)
    public String getBaiduurl(){
//        return "hello";
        return baiduurl;
    }

}

======================

But when I use like this, the variabe "baiduurl" can not be resolved:

package com.lanyyyy.springdemo.service;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;

@PropertySource("classpath:application.properties")
public class UrlService {
    @Value("${baiduurl}")
    public String baiduurl;

    //    @RequestMapping(path="/getbaidu", method=RequestMethod.GET)
    public String getBaiduurl() {
        return baiduurl;
    }
}

Is there anything wrong????? Or I use the @Value wrong?????

In my applicaiton.properties:

baiduurl=http://www.baidu.com
server.port=8888

Upvotes: 0

Views: 474

Answers (1)

Mạnh Quyết Nguyễn
Mạnh Quyết Nguyễn

Reputation: 18235

When you annotated your controller as @RestController then your class will become a @Controller

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController

A @Controller annotated class is a @Component:

@Documented
@Component
public @interface Controller

During component scan, spring container will initialize your class, @Autowire fields and inject @Value

In your second example, your UrlService is not a bean so no binding/injecting is done.

You should mark your service with @Service (or other marker like @Component...) to have the spring container injected baiduurl value for you.

Upvotes: 5

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