How to make JsonGenerator pretty-print Date and DateTime values?

Question

I'm using this method to convert any object to a json string:

private String objectToJson(Object object) throws IOException {
        // write JSON
        StringWriter writer = new StringWriter();
        ObjectMapper mapper = new ObjectMapper();
        final JsonGenerator jsonGenerator = mapper.getJsonFactory().createJsonGenerator(writer);
        jsonGenerator.setPrettyPrinter(new DefaultPrettyPrinter());

        mapper.writeValue(jsonGenerator, object);
        return writer.toString();
    }

When the object being printed contains fields that are java.util.Date or jodatime's DateTime, the printed value is the number of milliseconds since the epoch. I would like, instead, to pretty-print them in a standard "HH:MM:SS" notation. How should I go about doing this?

Answer 1

This was already mentioned in FAQ first answer points to, but just in case: you can choose between numeric and textual representation (numeric being used by default since it is much faster) by using this feature:

objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS, false);

doing this will use the default date format, which you can then redefine as mentioned (with setDateFormat).

Also: you can simplify you code like so:

ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationConfig.Feature.INDENT_OUTPUT, true);
mapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS, false);
return mapper.writeValueAsString(object);

instead of using StringWriter and JsonGenerator explicitly.