Spring Boot @Value 注解返回 null

Question

I'm trying to put api key in application.properties and get api key from it.

So I put api key in application.properties.

application.properties

server.port=8090

#My Key will be placed in here
shortweather.key=myapikey

And then I made a class to get api key from application.properties

ApiKey.java class

package com.wook.weather;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class ApiKey {
    @Value("${shortweather.key}")
    private String apiKey;

    public String getApiKey() {
        return apiKey;
    }

    @Override
    public String toString() {
        return "ApiKey [apiKey=" + apiKey + "]";
    }
    
}

And I made an instance at main method and try to call getApiKey()

Application.java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.util.DefaultUriBuilderFactory;

@SpringBootApplication
public class Application {

    private final static String BASE_URL = "http://apis.data.go.kr/1360000/VilageFcstInfoService_2.0";
    
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
        
        String serviceKey = "apikey";
        String pageNo = "1";
        String numOfRows = "12";
        String dataType = "JSON";
        String base_date = "20211020";
        String base_time = "2300";
        String nx = "55";
        String ny = "127";

        DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(BASE_URL);
        factory.setEncodingMode(DefaultUriBuilderFactory.EncodingMode.VALUES_ONLY);

        WebClient wc = WebClient.builder().uriBuilderFactory(factory).baseUrl(BASE_URL).build();

        String response = wc.get()
                .uri(uriBuilder -> uriBuilder.path("/getVilageFcst")
                        .queryParam("serviceKey", serviceKey)
                        .queryParam("numOfRows", numOfRows)
                        .queryParam("pageNo", pageNo)
                        .queryParam("dataType", dataType)
                        .queryParam("base_date", base_date)
                        .queryParam("base_time", base_time)
                        .queryParam("nx", nx)
                        .queryParam("ny", ny).build())
                .retrieve().bodyToMono(String.class).block();

        System.out.println(response);
        
        
        //I made ApiKey instance here
        ApiKey apk = new ApiKey();
        //This part return null
        System.out.println(apk.getApiKey());
    }
}

But I get null.

I want to get value that is in application.properties.

How can I fix this issue?

Answer 1

Spring only injects value while the bean is managed by spring. You are creating an instance of the bean by calling new. This is where you are taking control of yourself and spring is no longer able to inject value. Rather you should do this:

@AutoWired
private ApiKey apk;

And also you marked the ApiKey class with @Component. So, spring will create an instance and then inject it to the main call by auto wiring. And when spring takes control over instantiation, you will get your desired value.

Complete code:

    @SpringBootApplication
    public class Application implements CommandLineRunner {
    
        private final ApiKey apk;
    
        public Application( ApiKey apk ) {
            this.apk = apk;
        }
    
    
        public static void main( String[] args ) {
            SpringApplication.run(Application.class, args);
        }
    
        @Override
        public void run( String... args ) throws Exception {
            
            String serviceKey = "apikey";
            String pageNo = "1";
            String numOfRows = "12";
            String dataType = "JSON";
            String base_date = "20211020";
            String base_time = "2300";
            String nx = "55";
            String ny = "127";
    
            DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(BASE_URL);
            factory.setEncodingMode(DefaultUriBuilderFactory.EncodingMode.VALUES_ONLY);
    
            WebClient wc = WebClient.builder().uriBuilderFactory(factory).baseUrl(BASE_URL).build();
    
            String response = wc.get()
                    .uri(uriBuilder -> uriBuilder.path("/getVilageFcst")
                            .queryParam("serviceKey", serviceKey)
                            .queryParam("numOfRows", numOfRows)
                            .queryParam("pageNo", pageNo)
                            .queryParam("dataType", dataType)
                            .queryParam("base_date", base_date)
                            .queryParam("base_time", base_time)
                            .queryParam("nx", nx)
                            .queryParam("ny", ny).build())
                    .retrieve().bodyToMono(String.class).block();
    
            System.out.println(response);
            System.out.println(apk.getApiKey());
        }
    }