将特定 JSON 映射到 Java 对象

Question

我正在尝试将特定 JSON 映射到我的 Java 模型 class。并且无法将其映射到 Java 对象。

我正在使用 fasterxml (jackson) 将 JSON 映射到我下面的 Java 模型 class - CurrencyModel.java。这个 JSON 开头有 '[' 这可能意味着它是一个数组。我无法将其映射到我的 class、CurrencyModel.java

import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.List;

class CurrencyModel {
    protected List<Currencies> currencies;
    protected List<CurrenciesRates> currenciesRates;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class Currencies {
        @JsonProperty("table")
        private String table;

        @JsonProperty("no")
        private String no;

        @JsonProperty("effectiveDate")
        private String effectiveDate;

        @JsonProperty("rates")
        private ArrayList<CurrencyRatesModel> rates;
    }

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class CurrenciesRates {
        @JsonProperty("currency")
        private String currency;

        @JsonProperty("code")
        private String code;

        @JsonProperty("mid")
        private String mid;
    }
}

并且在下面的字符串变量

中有 JSON

[
  {
    "table": "A",
    "no": "064/A/NBP/2013",
    "effectiveDate": "2013-04-02",
    "rates": [
      {
        "currency": "bat (Tajlandia)",
        "code": "THB",
        "mid": 0.1108
      },
      {
        "currency": "dolar amerykański",
        "code": "USD",
        "mid": 3.2552
      },
      {
        "currency": "dolar australijski",
        "code": "AUD",
        "mid": 3.4048
      }
    ]
  }
]

我正在尝试运行此代码使用：

ObjectMapper objectMapper = new ObjectMapper();
final String output = "[{\"table\": \"A\", \"no\": \"064/A/NBP/2013\",\"effectiveDate\": \"2013-04-02\",\"rates\": [{\"currency\": \"bat (Tajlandia)\",\"code\": \"THB\",\"mid\": 0.1108},{\"currency\": \"dolar amerykański\",\"code\": \"USD\",\"mid\": 3.2552},{\"currency\": \"dolar australijski\",\"code\": \"AUD\",\"mid\": 3.4048}]}]";
List<CurrencyModel> currencyModelList = Arrays.asList(objectMapper.readValue(output, CurrencyModel.class));
objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
System.out.println(currencyModelList.toArray());

导致错误：

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `` out of START_ARRAY token

Answer 1

我发现你的 java class 有问题。我已经执行了您的输入 json 并附带了下面提到的 java class 映射。

@Data
@NoArgsConstructor
@AllArgsConstructor

public class CurrencyModel {

    @JsonProperty("table")
    private String table;

    @JsonProperty("no")
    private String no;

    @JsonProperty("effectiveDate")
    private String effectiveDate;

    @JsonProperty("rates")
    private ArrayList<CurrenciesRates> rates;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class CurrenciesRates {
        @JsonProperty("currency")
        private String currency;

        @JsonProperty("code")
        private String code;

        @JsonProperty("mid")
        private String mid;
    }
}

还有你的主要 class,

ObjectMapper objectMapper = new ObjectMapper();
        final String output = "[{\"table\": \"A\", \"no\": \"064/A/NBP/2013\",\"effectiveDate\": \"2013-04-02\",\"rates\": [{\"currency\": \"bat (Tajlandia)\",\"code\": \"THB\",\"mid\": 0.1108},{\"currency\": \"dolar amerykański\",\"code\": \"USD\",\"mid\": 3.2552},{\"currency\": \"dolar australijski\",\"code\": \"AUD\",\"mid\": 3.4048}]}]";

        List<CurrencyModel> myObjects = objectMapper.readValue(output, new TypeReference<List<CurrencyModel>>() {
        });

Answer 2

您的 json 包含对象列表。所以使用 TypeReference

ObjectMapper objectMapper = new ObjectMapper();
    final String output = "[{\"table\": \"A\", \"no\": \"064/A/NBP/2013\",\"effectiveDate\": \"2013-04-02\",\"rates\": [{\"currency\": \"bat (Tajlandia)\",\"code\": \"THB\",\"mid\": 0.1108},{\"currency\": \"dolar amerykański\",\"code\": \"USD\",\"mid\": 3.2552},{\"currency\": \"dolar australijski\",\"code\": \"AUD\",\"mid\": 3.4048}]}]";
    objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
    List<CurrencyModel> currencyModelList = objectMapper.readValue(output, new TypeReference<List<CurrencyModel.Currencies>>(){});
    System.out.println(currencyModelList);

将特定 JSON 映射到 Java 对象

Mapping specific JSON to Java object

java

mapping

json

fasterxml