使用LocalDateTime字段將JSON反序列化為對象

Question

我放棄了 我已經瀏覽了所有可能的SO頁面，但是無法正常工作。

我有一個這樣的ConfigKeyVal類：

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class ConfigKeyValue {

    private String name;
    private NssConfigDto value;
}

Config類如下所示：

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class Config {

    private String name;
    private String source;
    private String destination;
    private int cycle;
    private LocalDateTime fixedTime;
    private LocalDateTime submitDate;
}

我正在嘗試將ConfigKeyVal （頂級）對象的JSON數組直接反序列化到我的ArrayList中。

public class ConfigKeyValueList extends ArrayList<ConfigKeyValue> {
    public ConfigKeyValueList() {
        super();
    }
}

像這樣：

final Data values = result.results().get("attributes"); // this is an array of ConfigKeyValue objects
ObjectMapper mapper = new ObjectMapper();
ConfigKeyValueList configKeyValueList = new ConfigKeyValueList();
try {
    configKeyValueList = mapper.readValue(values.asText(), ConfigKeyValueList.class);
} catch (IOException e) {
    e.printStackTrace();
}

我已經嘗試使用mapper.registerModule(new JavaTimeModule()); 但這沒有幫助。 我是否需要為此編寫自己的解串器，或者是否有有效的工具，但我做錯了所有事情？

我收到的錯誤是： com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of java.time.LocalDateTime: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?))

我在gradle文件中使用了那些jackson依賴項：

compile group: 'com.fasterxml.jackson.module', name: 'jackson-module-parameter-names', version: '2.9.6'
compile group: 'com.fasterxml.jackson.datatype', name: 'jackson-datatype-jdk8', version: '2.9.6'
compile group: 'com.fasterxml.jackson.datatype', name: 'jackson-datatype-jsr310', version: '2.9.6'

編輯：這就是JSON的樣子

[
    {
        "name": "kek1",
        "value": {
            "name": "kek1",
            "source": "source",
            "destination": "dest",
            "cycle": 1,
            "fixedTime": {
                "year": 2017,
                "month": "APRIL",
                "dayOfYear": 95,
                "dayOfWeek": "WEDNESDAY",
                "dayOfMonth": 5,
                "monthValue": 4,
                "hour": 4,
                "minute": 20,
                "second": 0,
                "nano": 0,
                "chronology": {
                    "id": "ISO",
                    "calendarType": "iso8601"
                }
            },
            "submitDate": {
                "year": 2017,
                "month": "APRIL",
                "dayOfYear": 95,
                "dayOfWeek": "WEDNESDAY",
                "dayOfMonth": 5,
                "monthValue": 4,
                "hour": 4,
                "minute": 20,
                "second": 0,
                "nano": 0,
                "chronology": {
                    "id": "ISO",
                    "calendarType": "iso8601"
                }
            }
        }
    },
    {
        "name": "kek2",
        "value": {
            "name": "kek2",
            "source": "source",
            "destination": "dest",
            "cycle": 1,
            "fixedTime": {
                "year": 2017,
                "month": "APRIL",
                "dayOfYear": 93,
                "dayOfWeek": "MONDAY",
                "dayOfMonth": 3,
                "monthValue": 4,
                "hour": 5,
                "minute": 10,
                "second": 0,
                "nano": 0,
                "chronology": {
                    "id": "ISO",
                    "calendarType": "iso8601"
                }
            },
            "submitDate": {
                "year": 2017,
                "month": "APRIL",
                "dayOfYear": 93,
                "dayOfWeek": "MONDAY",
                "dayOfMonth": 3,
                "monthValue": 4,
                "hour": 5,
                "minute": 10,
                "second": 0,
                "nano": 0,
                "chronology": {
                    "id": "ISO",
                    "calendarType": "iso8601"
                }
            }
        }
    }
]

Answer 1

首先，我不建議像這樣序列化日期。 我強烈建議您堅持使用標准，並使用RFC 3339和xkcd 1179認可的ISO 8601 ：

---

如果您可以控制JSON序列化

如果使用Spring Data MongoDB ，則可以使用MongoCustomConversions為您處理從Date和LocalDateTime進行的轉換：

@Configuration
public class MongoConfiguration {

    @Bean
    public MongoCustomConversions customConversions() {
        List<Converter<?, ?>> converters = new ArrayList<>();
        converters.add(new DateToLocalDateTimeConverter());
        converters.add(new LocalDateTimeToDateConverter());
        return new MongoCustomConversions(converters);
    }

    class DateToLocalDateTimeConverter implements Converter<Date, LocalDateTime> {

        @Override
        public LocalDateTime convert(Date source) {
            return source == null ? null : 
                LocalDateTime.ofInstant(source.toInstant(), ZoneId.systemDefault());
        }
    }

    class LocalDateTimeToDateConverter implements Converter<LocalDateTime, Date> {

        @Override
        public Date convert(LocalDateTime source) {
            return source == null ? null : Date.from(source.toInstant());
        }
    }
}

然后，您可以在bean中使用LocalDateTime ，讓Jackson和JavaTimeModule處理序列化/反序列化：

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

// Serialize
List<ConfigKeyValue> list = null;
String json = mapper.writeValueAsString(list);

// Deserialize
TypeReference<List<ConfigKeyValue>> typeRef = new TypeReference<>() {};
list = mapper.readValue(json, typeRef);

---

處理您擁有的東西

如果您無法控制JSON，則需要一個自定義解串器 。 實現可以像這樣：

public class CustomLocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {

    @Override
    public LocalDateTime deserialize(JsonParser jp, DeserializationContext ctxt)
            throws IOException {

        JsonNode tree = jp.getCodec().readTree(jp);
        int year = tree.get("year").asInt();
        int month = tree.get("monthValue").asInt();
        int dayOfMonth = tree.get("dayOfMonth").asInt();
        int hour = tree.get("hour").asInt();
        int minute = tree.get("minute").asInt();
        int second = tree.get("second").asInt();
        int nano = tree.get("nano").asInt();

        return LocalDateTime.of(year, month, dayOfMonth, hour, minute, second, nano);
    }
}

然后注釋您的字段以使用上面定義的反序列化器：

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class Config {

    // Other fields

    @JsonDeserialize(using = CustomLocalDateTimeDeserializer.class)
    private LocalDateTime fixedTime;

    @JsonDeserialize(using = CustomLocalDateTimeDeserializer.class)
    private LocalDateTime submitDate;
}

最后解析您的JSON文檔：

ObjectMapper mapper = new ObjectMapper();

TypeReference<List<ConfigKeyValue>> typeRef = new TypeReference<>() {};
List<ConfigKeyValue> list = mapper.readValue(json, typeRef);

Answer 2

您必須將模塊添加到您的ObjectMapper

private ObjectMapper getMapper() {
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(SerializationFeature.INDENT_OUTPUT,false);
    mapper.setSerializationInclusion(Include.NON_NULL);
    mapper.registerModule(new JavaTimeModule());
    mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    return mapper;
}

由於傑克遜的最新版本是JavaTimeModule，所以以前是JSR310Module

編輯：應該同時用於序列化/反序列化，您可能會誤解的是mapper.configure（SerializationFeature.WRITE_DATES_AS_TIMESTAMPS，false）;。

JSON格式應為ISO：

{
    "name": "kek2",
    "value": {
        "name": "kek2",
        "source": "source",
        "destination": "dest",
        "cycle": 1,
        "fixedTime": "2018-07-17T15:10:55"
...

Answer 3

Jackson沒有辦法從任何JSON字符串值反序列化LocalDateTime對象。

將LocalDateTime對象更改為“ String”。