Java Spring 引导消耗 API 嵌套 object 返回 NULL

Question

I'm playing around with spring boot trying to consume a third parties rest api.

The API call I'm using returns the below JSON object.

{"success":true,"terms":"https:\/\/coinlayer.com\/terms","privacy":"https:\/\/coinlayer.com\/privacy","timestamp":1645616586,"target":"USD","rates":{"BTC":39049.424242}}

My code successfully consumes this JSON object however it returns this.

LiveData{success='true'terms='https://coinlayer.com/terms'privacy='https://coinlayer.com/privacy'timestamp='1645619886'target='EUR'rates={BTC='null'}}

Note that rates={BTC='null'} should be rates={BTC='39049.424242'}. Any help is greatly appreciated.

Below is my code

LiveData.java

package com.example.consumingrest;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class LiveData {

    private Boolean success;
    private String terms;
    private String privacy;
    private Long timestamp;
    private String target;
    private Rates rates;

    public LiveData() {
    }

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public String getTerms() {
        return terms;
    }

    public void setTerms(String terms) {
        this.terms = terms;
    }

    public String getPrivacy() {
        return privacy;
    }

    public void setPrivacy(String privacy) {
        this.privacy = privacy;
    }

    public Long getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(Long timestamp) {
        this.timestamp = timestamp;
    }

    public String getTarget() {
        return target;
    }

    public void setTarget(String target) {
        this.target = target;
    }

    public Rates getRates() {
        return rates;
    }

    public void setValue(Rates rates) {
        this.rates = rates;
    }

    @Override
    public String toString() {
        return "LiveData{" +
                "success='" + success + '\'' +
                "terms='" + terms + '\'' +
                "privacy='" + privacy + '\'' +
                "timestamp='" + timestamp + '\'' +
                "target='" + target + '\'' +
                "rates=" + rates +
                '}';
    }
}

Rates.java

package com.example.consumingrest;
import java.math.BigDecimal;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Rates {

    private BigDecimal BTC;

    public Rates() {
    }

    public BigDecimal getBTC() {
        return this.BTC;
    }

    public void setId(BigDecimal BTC) {
        this.BTC = BTC;
    }


    @Override
    public String toString() {
        return "{" +
                "BTC='" + BTC + '\''+
                '}';
    }
}

ConsumingRest.java (main)

package com.example.consumingrest;

import java.time.LocalDate;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class ConsumingRestApplication {

    private static final Logger log = LoggerFactory.getLogger(ConsumingRestApplication.class);

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

    @Bean
    public RestTemplate restTemplate(RestTemplateBuilder builder) {
        return builder.build();
    }

    @Bean
    public CommandLineRunner run(RestTemplate restTemplate) throws Exception {
        return args -> {
            LiveData liveData = restTemplate.getForObject(
                    "http://api.coinlayer.com/api/live?access_key=121a4df8b95fd5be872da3bad101cd73&target=EUR&symbols=BTC", LiveData.class);
            log.info(liveData.toString());
        };
    }
}

Answer 1

You can user @JsonProperty annotation.

@JsonProperty(value = "BTC")
BigDecimal btc;

it is not camel case that is the reason it is null also some fields can be problematic as well. It is better to write annotation to those attributes which is problematic.