JacksonInject + JsonCreator + Spring Boot

[eric liprandi]

Hi,

StackOverflow question posted here

Cleaning up some code that is currently manually parsing various JSON objects. It's all been pretty straightforward with one exception. I have 1 object left that has a property that is a string containing JSON. I need to parse that string. I think the correct solution is to create a custom deserializer for that. My refactoring has already caused much more changes than what the team is comfortable with, so I am trying to skip the custom deserializer.

My alternative is to try and use `@JacksonInject` and to have `ObjectMapper` injected. Assuming that my Spring Boot application is properly auto-configured with no customization to the `ObjectMapper`, it should work out-of--the-box, correct?

I am getting errors both at runtime and in my tests (using `@JsonTest` and `JacksonTester`). In both cases, it appears that the system is trying to deserialize the `ObjectMapper` from the JSON string and is complaining about Conflicting setters like:
"Conflicting setter definitions for property "defaultPropertyInclusion": com.fasterxml.jackson.databind.ObjectMapper#setDefaultPropertyInclusion(com.fasterxml.jackson.annotation.JsonInclude$Value) vs com.fasterxml.jackson.databind.ObjectMapper#setDefaultPropertyInclusion(com.fasterxml.jackson.annotation.JsonInclude$Include)

"

Thanks in advance for any help.

Eric.

[Tatu Saloranta]

Injecting `ObjectMapper` should be possible, yes, but not for property
that comes from JSON.
(since otherwise Jackson will indeed try to deserialize JSON into
`ObjectMapper` and that's not what you want).
But even if you inject a mapper, something would need to use it. So it
is probably not a working solution for your problem.
This is based on some guessing based on description (since there's no code).

On custom deserializer: you probably know it but just in case: there
are multiple ways to register custom deserializers: so instead of
global registration you can use:

@JsonDeserialize(using = MyJsonInJsonDeserializer)
private CustomType values;

But thinking out loud, I wonder if you could instead define a
`Converter` that takes in, say `JsonNode` (or `String`) and then
handles secondary conversion.

@JsonDeserialize(convert = FromJsonConverter.class)
private CustomType values;

where FromJsonConverter would implement `Converter<String, CustomType>`.
... but it still does need `ObjectMapper`, which won't be available
via `DeserializationContext`.
... unless you pass one as Contextual Attribute (see
`ObjectReader.withAttribute(...)`)

-+ Tatu +-

ps. The case of "JSON in JSON" (or "XML in JSON" or generally "X in Y"
for Jackson-supported formats X and Y) is sort of a long-term request
that has never been properly addressed. Assuming I did not misread
the use case here.

[eric liprandi]

Tatu,

Thank you for quick response. I will dig into this a bit. I think ultimately, a custom deserializer/converter is going to be the cleanest approach.

Regards,

Eric.