Support for @JsonValue custom ID types

[marquiswang]

I'm finally trying to migrate from 2.x. I have a lot of code of the form:

JacksonDBCollection.wrap(collection, SomeType.class, CustomId.class, objectMapper);

where CustomId is a class with @JsonValue and @JsonCreator annotations that allow Jackson to serialize it to a string. With 2.x, this was supported and used the String serialization of CustomId as the id.

With 3.x and 4.x, the generic key type has been removed from JacksonMongoCollection, and I get the following error when trying to insert:

java.lang.IllegalArgumentException: Unsupported ID type: class foo.bar.CustomId

Is there any way to get the equivalent old functionality?

[rlodge]

Not at this time, at least not without fakery inside the class (like declaring the _id field as String and then converting to/from it...)

[marquiswang]

Thanks, that's what I was afraid of. Is this something that could be added?

[rlodge]

I think so. It involves determining if the jackson-converted value will be something mongo will use as an id, though, so the solution will have to be thought through a bit. I played with some options this morning but I don't know if I like them.

[marquiswang]

I managed to make it work by adding

try {
    final String stringRepresentation = objectMapper.writer().writeValueAsString(value);
    if (stringRepresentation.startsWith("\"") && stringRepresentation.endsWith("\"")) {
        return new BsonString(stringRepresentation.substring(1, stringRepresentation.length() - 1));
    }
} catch (JsonProcessingException aE) {
    throw new RuntimeException(aE);
}

at the bottom of JacksonCodec#constructIdValue. I don't know if there is a more elegant way to determine if Jackson thinks an object should be serialized as a non-object type (I'm only interested in Strings here, but obviously we could detect numeric types too).

[rlodge]

I did something a bit similar:

           try {
                final JsonNode tree = objectMapper.valueToTree(value);
                if (tree.isTextual()) {
                    return new BsonString(tree.asText());
                }
            } catch (RuntimeException e) {
                throw new IllegalArgumentException(String.format("Unsupported ID type: %s", value.getClass()), e);
            }

And I wrote some tests.

But I wanted to support the other types and I ran into test problems that seem related to newer JDKs, and then I had to move onto assigned work. :) I'll see if I can get to it more seriously soon.

[marquiswang]

I'm afraid to report that I've found further code in my codebase (yay legacy codebases) that uses an id field with an object, which apparently mongojack 2.x and Mongo happily allow (totally didn't know that).

> db.foo.bar.findOne()
{
	"_id" : {
		"foo" : "bar",
		"date" : [
			2016,
			4,
			5
		]
	},
	"offset" : 123.456
}

If we want MongoJack to support this... that would be really nice (and backwards compatible with 2.x!). Though I could understand if you didn't want to.

(BTW, I found that any version of Jackson below 2.13.3 does not work with Java 17, in case that's what you're running into)

[marquiswang]

I found that this works

        final JsonNode tree = objectMapper.valueToTree(value);
        if (tree.isDouble()) {
            return new BsonDouble(tree.asDouble());
        } else if (tree.isTextual()) {
            return new BsonString(tree.asText());
        } else if (tree.isInt()) {
            return new BsonInt32(tree.asInt());
        } else if (tree.isLong()) {
            return new BsonInt64(tree.asLong());
        } else if (tree.isBigDecimal()) {
            return new BsonDecimal128(new Decimal128(tree.decimalValue()));
        } else {
            return BsonDocument.parse(tree.toString());
        }

[rlodge]

I have published a 4.5.1-SNAPSHOT version that I believe fixes this. Please let me know if it works for you.

[marquiswang]

Thanks so much! Trying this out now.

[marquiswang]

This does appear to work for me! Thanks!

[rlodge]

Fix deployed 4.5.1 and 4.7.0

[marquiswang]

Thank you!