Error response that's not a Problem can't be treated by Jackson 3

[pvdbosch]

I'm testing impact of Jackson 3.

There's an issue occurring when an API returns a 4xx/5xx status without a "status" property in the JSON payload.
Problem has a status with int type. When the property is absent from the JSON payload, it can't be set to null.

Caused by: tools.jackson.databind.exc.MismatchedInputException: Cannot map `null` into type `int` (set DeserializationConfig.DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES to 'false' to allow)
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); byte offset: #1] (through reference chain: io.github.belgif.rest.problem.DefaultProblem["status"])
	at tools.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:67)

This is different from Jackson 2 behavior , where the default config for FAIL_ON_NULL_FOR_PRIMITIVES was false. It'll probably set status to 0 if it's absent (haven't tested). The new Jackson 3 behavior does make sense to me.

What would be the best solution?

• We set the status to the http header's status when it's absent from the payload?
• Change the type of status to Integer and set it to null?
• Set to 0 when absent?
  • note: @JsonProperty(value = "status", defaultValue = "0") doesnt work. defaultValue is only for documentation, not deserialization

[jpraet]

I think only DefaultProblem is impacted by this. For the other problems, the status is initialized in the constructor. There is no setStatus().

rest-problem-java/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/api/Problem.java

Lines 38 to 39 in 5b4d9e2

	// - "status" is also an unknown property, because we don't have a setStatus()
	ignoreUnknown = true)

In DefaultProblem we have

rest-problem-java/belgif-rest-problem/src/main/java/io/github/belgif/rest/problem/DefaultProblem.java

Lines 24 to 26 in 5b4d9e2

	@JsonCreator
	public DefaultProblem(@JsonProperty("type") URI type, @JsonProperty("href") URI href,
	@JsonProperty("title") String title, @JsonProperty("status") int status) {

Minimal change to get it working could be to update from int to Integer there, and pass 0 to the super constructor if it's null?

But I do also like your idea of using the HTTP status if it's absent from the payload.
That looks a bit more challenging to implement though.

[pvdbosch]

I've pushed the 'minimal change' solution mistakenly to main instead of a PR. Build succeeds. Does it look good to you?
I can push a rollback commit and create a PR if needed.

To override it by the http status code is indeed more challenging. We could also think how to handle it when it's there but inconsistent with the actual HTTP status, both in case of a DefaultProblem, as a supported problem type.

[jpraet]

The jackson 3 issue is fixed. Remaining concerns extracted to #283.