Jackson-databind: SqlDateSerializer does not obey SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS

[BrentDouglas]

This can result in inconsistent serialization of date depending on their origin.

[cowtowncoder]

Oh. Now I remember what the issue was -- since originally regular java.util.Date default to numeric serialization, and java.sql.Date, there is/was no way to tell difference between "default" value and explicit forcing of numeric serialization.
So what we got here is a backwards-incompatibility in the making: I think the fix will need to go in 2.3, and can't be done in a patch.

There is also the additional question of formatting to use (default for sql.Date is to only use date part, no time); but that's probably lesser deal.

[cowtowncoder]

One relevante note: as of Jackson 2.6, it is possible to use @JsonFormat(shape=JsonFormat.Shape.NUMBER) to force serialization of java.sql.Dates as timestamps. Plan is to also allow some way to define per-type format defaults, to allow overriding global defaults.

I am still not sure whether the global default itself should be changed, leaving this issue open.

[cowtowncoder]

And with Jackson 2.8, it is possible to specify "config overrides", using ObjectMapper.configOverrides().setFormat().

But perhaps we could actually change defaults for 2.9, finally.

[PatrickGotthard]

Hi, is this the correct config to restore the default behaviour of 2.8.x in 2.9.x?

final ObjectMapper mapper = new ObjectMapper();
mapper.configOverride(java.sql.Date.class).setFormat(JsonFormat.Value.forPattern("yyyy-MM-dd"));

[cowtowncoder]

@PatrickGotthard Yes, although use of shape does allow switching between number/String representation. Setting of pattern does implicitly also choose String so yes that should work.

[bkrieger]

@cowtowncoder mapper.configOverride(java.sql.Date.class).setFormat(JsonFormat.Value.forPattern("yyyy-MM-dd")) didn't work for me - java.sql.Date still serialized as a timestamp. Looking at the code, it looks like it's because the custom format isn't actually added to SqlDateSerializer except in the createContextual method (https://github.com/FasterXML/jackson-databind/blob/master/src/main/java/com/fasterxml/jackson/databind/ser/std/DateTimeSerializerBase.java#L59).

For now, I've reverted this behavior with

mapper.registerModule(new SimpleModule() {
            {
                addSerializer(
                        java.sql.Date.class,
                        new SqlDateSerializer().withFormat(false, new SimpleDateFormat("yyyy-MM-dd"))
                );
            }
        });

but it seems pretty hacky so I'd prefer the other method if possible. Do you have any thoughts?

[cowtowncoder]

@bkrieger Sounds plausible. Could you please file a new issue, so it's easier to track fixes.

[bkrieger]

Done, https://github.com/FasterXML/jackson-databind/issues/2064.

[limkl-psa]

Would this be considered a breaking change or incompatibility migrating from jackson-databind 2.8 to 2.9?