使用 RestTemplate 将 JSON 映射到对象

Question

我编写了货币转换器程序，它JSON从api.fixer.io、映射对象中读取并创建选定汇率的简单数据集。我的程序运行良好，直到我停止使用Jackson解析和映射对象并将其替换为RestTemplate. 它可以很好地读取基础货币和日期，但不能很好地读取Rates子对象。为什么？

我的代码： Currency类：

package com.github.gromo13.currencyConverter.model.util;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Currency {
    private String base;
    private String date;
    private Rates rates;

    public Currency() {

    }

    public String getBase() {
        return this.base;
    }

    public void setBase(String base) {
        this.base = base;
    }

    public String getDate() {
        return this.date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public Rates getRates() {
        return this.rates;
    }

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

    public double getRate(String currencyCode) {
        return rates.getRate(currencyCode);
    }
}

Rates 班级：

package com.github.gromo13.currencyConverter.model.util;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Rates {
    private double eur;
    private double pln;
    private double usd;

    public double getEur() {
        return this.eur;
    }

    public void setEur(double eur) {
        this.eur = eur;
    }

    public double getPln() {
        return this.pln;
    }

    public void setPln(double pln) {
        this.pln = pln;
    }

    public double getUsd() {
        return this.usd;
    }

    public void setUsd(double usd) {
        this.usd = usd;
    }

    public double getRate(String currencyCode) {
        currencyCode = currencyCode.toUpperCase();
        switch (currencyCode) {
            case "EUR":
                return this.eur;
            case "PLN":
                return this.pln;
            case "USD":
                return this.usd;
            default:
                return 1;
        }
    }
}

Repository必须Currency使用RestTemplate以下方法映射对象的类：

package com.github.gromo13.currencyConverter.repository;

import com.github.gromo13.currencyConverter.model.util.Currency;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import org.springframework.web.client.RestTemplate;

@Repository
public class FixerIoCurrencyRepository implements CurrencyRepository {
    @Autowired
    private RestTemplate restTemplate;

    public void setRestTemplate(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    @Override
    public Currency getCurrency(String currencyCode) {
        Currency currency = restTemplate.getForObject("http://api.fixer.io/latest?base={currencyCode}", Currency.class, currencyCode);

        return currency;
    }
}

我试图解析和映射的示例 JSON 数据

我正在使用此Currency对象准备DataSet带有简单地图的对象，<currencyName, rate>并将其打印在视图中的表格中。一切正常，我每次都收到0每种货币的汇率。

Answer 1

问题是Rates类中的属性是小写的，而 JSON 数据是大写的。

您可以在@Configuration类中定义RestTemplate使用ObjectMapper不区分大小写的接受属性。这样，您就不必更改Rates属性的格式。

@Bean
public ObjectMapper objectMapper() {
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
    return mapper;
}

@Bean
public MappingJackson2HttpMessageConverter mappingJacksonHttpMessageConverter() {
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(objectMapper());
    return converter;
}

@Bean
public RestTemplate restTemplate() {
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(0, mappingJacksonHttpMessageConverter());
    return restTemplate;
}