我有一個(gè) JSON 示例{ "data":"some string data", "amount":200, "amountCurrencyList":[ {"value":4000.0,"currency":"USD"}, {"value":100.0,"currency":"GBP"} ]}以及當(dāng)前將其解析為基礎(chǔ)對象的映射字段的方法public void buildDetailsFromJson(String details) { if (details != null) { TypeReference<HashMap<String, Object>> mapTypeReference = new TypeReference<HashMap<String, Object>>() { }; ObjectMapper mapper = new ObjectMapper(); try { mapper.enable(DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY); mapper.disable(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES); detailsMap = mapper.readValue(details, mapTypeReference); } catch (IOException e) { log.error("Exception during JSON {} parsing! {}", details, e.getMessage()); } }}JSON 結(jié)構(gòu)可以更改。想法是有一個(gè)單獨(dú)的方法，理想情況下可以輕松提取所需的參數(shù)，例如map.get(key_name)例如public void setUpFieldsFromMap() { HashMap<String, Object> map = super.detailsMap; this.amountCurrencyList = (ArrayList<MoneyValue>) map.get("amountCurrencyList"); if (isNull(amountCurrencyList)) { throw new InvalidOrMissingParametersException("Exception during JSON parsing! Critical data is missing in DetailsMap - " + map.toString()); }}因此，通過按鍵獲取 List 對象并將其轉(zhuǎn)換為所需的參數(shù)。但是當(dāng)我嘗試操作時(shí)List<MoneyValue>System.out.println(detailsObj.getAmountCurrencyList().get(0).getValue());我越來越Exception: java.util.LinkedHashMap cannot be cast to MoneyValue實(shí)際上是否有可能實(shí)現(xiàn)我想要的，而無需使用精確的參數(shù)對 TypeReference 進(jìn)行硬編碼TypeReference<HashMap<String, List<MoneyValue>>>？UPDpublic class MoneyValue {@NotNullprivate BigDecimal value;@NotNullprivate String currency;EventDetails 類public class SomeEventDetails extends BaseEventDetails implements EventDetails {private ArrayList<MoneyValue> amountCurrencyList;
1 回答
泛舟湖上清波郎朗
TA貢獻(xiàn)1818條經(jīng)驗(yàn) 獲得超3個(gè)贊
如果一組屬性（我的意思是輸入數(shù)據(jù)的結(jié)構(gòu)）是不可修改的，我們可以將它表示為一個(gè) POJO 類。讓它成為DetailsData：
public class DetailsData {
private String data;
private BigDecimal amount;
private List<MoneyValue> amountCurrencyList;
/*getters, setters, constructors*/
public DetailsData() {
}
@JsonProperty("amountCurrencyList")
private void deserializeMoneyValue(List<Map<String, Object>> data) {
if (Objects.isNull(amountCurrencyList)) {
amountCurrencyList = new ArrayList<>();
} else {
amountCurrencyList.clear();
}
MoneyValue moneyValue;
for (Map<String, Object> item : data) {
moneyValue = new MoneyValue(getValue(item.get("value")),
(String) item.get("currency"));
amountCurrencyList.add(moneyValue);
}
}
private BigDecimal getValue(Object value) {
BigDecimal result = null;
if (value != null) {
if (value instanceof BigDecimal) {
result = (BigDecimal) value;
} else if (value instanceof BigInteger) {
result = new BigDecimal((BigInteger) value);
} else if (value instanceof Number) {
result = new BigDecimal(((Number) value).doubleValue());
} else {
throw new ClassCastException("Invalid value");
}
}
return result;
}
}
如您所見，這是一個(gè)deserializeMoneyValue注釋為 JSON 屬性的方法。因此，對于 ObjectMapper，它將用作自定義反序列化器。getValue方法是必要的，因?yàn)?Jackson 以這種方式工作，因此值將在滿足值大小的類中反序列化。例如，如果 value = "100" 它將被反序列化為Integer，如果 value = "100.0" -Double等等。其實(shí)這個(gè)方法你可以制作static并移動(dòng)到一些util類中?？偨Y(jié)一下，您可以buildDetailsFromJson通過以下方式進(jìn)行更改：
public void buildDetailsFromJson(String details) {
if (details != null) {
ObjectMapper mapper = new ObjectMapper();
try {
mapper.enable(DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
mapper.disable(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES);
// assuming the eventDetails is an instance of DetailsData
eventDetails = mapper.readValue(details, DetailsData.class);
} catch (IOException e) {
log.error("Exception during JSON {} parsing! {}", details, e.getMessage());
}
}
}
和 EventDetail 類：
public class SomeEventDetails extends BaseEventDetails implements EventDetails {
private List<MoneyValue> amountCurrencyList;
@Override
public void setUpFieldsFromMap() {
this.amountCurrencyList = super.eventDetails.getAmountCurrencyList();
if (isNull(amountCurrencyList)) {
throw new InvalidOrMissingParametersException("Exception during JSON parsing! Critical data is missing in DetailsMap - " + super.eventDetails.toString());
}
}
}
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