Spring MVC Json decoder to accept both string and long millis values

Question

Is there any way to make Spring decodes both string (es. yyyy-mm-dd HH:MM:ss) and long (unixtime milliseconds) for Date objects?

For what? Request parameters? Json bodies? XML? So depending on what you want the solution will differ. — M. Deinum
– M. Deinum, Commented Oct 29 at 10:31

Amario · Accepted Answer · 2025-10-28 12:23:36Z

1

You can register a custom Converter that tries both Unix timestamps and formatted strings. Simple example:

@Component
public class Converter implements Converter<String, Date> {

    private static final String[] FORMATS = {
        "yyyy-MM-dd HH:mm:ss",
        "yyyy-MM-dd'T'HH:mm:ss",
        "yyyy-MM-dd"...etc
    };

    @Override
    public Date convert(String source) {
            return new Date(Long.parseLong(source));

        for (String f : FORMATS) {
            return new SimpleDateFormat(f).parse(source);
        }
    }
}

Spring Boot will automatically pick this up for @RequestParam, @PathVariable, and @RequestBody bindings.

For LocalDateTime, just implement Converter<String, LocalDateTime> and use DateTimeFormatter / Instant.ofEpochMilli(). If you decide to use this snippet, make sure to use some try catches is my recommendation.

answered Oct 28 at 12:23

Amario

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2 Comments

M. Deinum Oct 29 at 10:32

This will not work with @RequestBody as that doesn't use a converter but Jackson (by default unless a different library is added and used). It will only work for request parameters, path variables and if you are luckily for header values.

Tobia Nov 19 at 15:21

Ok thanks, how can I let it work with requestbody?

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