Deserialize LocalDateTime with Jackson

Question

I have an error when I try to deserialize this attribute:

@JsonDeserialize(using = LocalDateTimeDeserializer.class)
@JsonSerialize(using = LocalDateTimeSerializer.class)
private LocalDateTime deliveryDate;

This is the deserialization class:

public class LocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {

    @Override
    public LocalDateTime deserialize(JsonParser parser, DeserializationContext context) throws IOException {

        if (parser.getCurrentToken().equals(JsonToken.VALUE_STRING)) {
            String rawDate = parser.getText();
            return LocalDateTime.parse(rawDate);
        } else {
            throw context.wrongTokenException(parser, JsonToken.VALUE_STRING, "Expected string.");
    }
}

And the serialization class:

public class LocalDateTimeSerializer extends JsonSerializer<LocalDateTime> {

    @Override
    public void serialize(LocalDateTime value, JsonGenerator gen, SerializerProvider serializers) throws IOException {

        gen.writeString(value.toString());
    }

This is the error I get:

"timestamp":1513962011642,"status":400,"error":"Bad Request","exception":"org.springframework.http.converter.HttpMessageNotReadableException","message":"Could not read document: Text '2017-12-22T16:00:00.874Z' could not be parsed, unparsed text found at index 23

Do you know why?

Thanks!

Possible duplicate of [Java 8 LocalDate Jackson format](https://stackoverflow.com/questions/28802544/java-8-localdate-jackson-format) — Sebastian D'Agostino, Dec 22 '17 at 17:55
What is the actual original data in the JSON? 1513962011642? — Basil Bourque, Dec 22 '17 at 18:00

Basil Bourque · Accepted Answer · 2017-12-26T16:53:37.880

tl;dr

Process as an Instant rather than LocalDateTime.

Instant.parse( "2017-12-22T16:00:00.874Z" )

Details

Not sure of your original data from JSON. If your input data is 1513962011642, it appears to be a count since an epoch, presumably an epoch reference date of 1970-01-01T00:00:00Z, the first moment of 1970 in UTC.

Instant instant = Instant.ofEpochMilli( 1_513_962_011_642L ) ;

If the original input is 2017-12-22T16:00:00.874Z, directly parse as an Instant. That string is in standard ISO 8601 format. The Z on the end is short for Zulu and means UTC.

The java.time classes use the standard formats by default when parsing/generating strings.

Instant instant = Instant.parse( "2017-12-22T16:00:00.874Z" ) ;

A LocalDateTime purposely lacks any concept of a time zone or offset from UTC, so it does not represent an actual moment and is not a point on the timeline. You are mistakenly trying to fit your value into the wrong class, where the fact it is a UTC value cannot be represented.

Instead, process that input as an Instant object. An instant represents a point on the timeline in UTC with a resolution of nanoseconds.

`timestamp` `1513962011642` is the time of http request which isn't related with text date string which produces the error. — Mikita Harbacheuski, Dec 22 '17 at 18:22

score 0 · Answer 2 · answered Dec 22 '17 at 17:31

0

Actually the error is pretty straightforward, it says that spring can't deserialize this string "2017-12-22T16:00:00.874Z" to LocalDateTime. If you will run the next code you will see the same error:

public static void main(String[] args) {
    System.out.println(LocalDateTime.parse("2017-12-22T16:00:00.874Z"));
}

The source of the error is character 'Z' at index 23. If you will remove this character the code above will work. So i would recommend you to check why this 'Z' character is present in the string while your serializer doesn't add it.

answered Dec 22 '17 at 17:31

Mikita Harbacheuski

2,193
8
16

1

Poor advice. Discarding the `Z` is throwing away information, the fact that this string represents a moment in UTC. The real issue is that the input should be processed as a `Instant` rather than as a `LocalDateTime`. – Basil Bourque Dec 22 '17 at 17:48
While i admit that Z can be present it the string i didn't suggest to remove it. And the question isn't about necessity of presence of this character. The question is - why the error occurs, the answer is - deserializer can't deserialize such string because of presence of Z character which isn't added during serialization. And advice is to figure out why it is present. Different format on server and client could be the reason but i can't be such categorial as you because i don't have enough details. – Mikita Harbacheuski Dec 22 '17 at 18:15
Thanks for the explanation :) – Anna Dec 26 '17 at 14:18

Deserialize LocalDateTime with Jackson

2 Answers2

tl;dr

Details