Frequently Asked Questions

Why am I getting a NoClassDefFoundError?

java.lang.NoClassDefFoundError: com/fasterxml/jackson/core/exc/InputCoercionException,
compiling:(jsonista/core.clj:79:38)

If you're getting this kind of error message when requiring jsonista.core or otherwise using jsonista (e.g. via muuntaja), the problem is that you're depending on different versions of jackson-core and jackson-databind. You need to depend on the same versions of both for jsonista to work correctly.

Run lein deps :tree (Leiningen users) or clj -Stree (deps.edn users) in your project and look for lines with com.fasterxml.jackson.core/jackson-core and com.fasterxml.jackson.core/jackson-core. If their versions do not match, that's the problem.

Possible solutions:

• Add the same versions of jackson-core and jackson-databind as dependencies for your project. For example, if you use Leiningen, add these lines to the :dependencies vector in your project.clj:

[com.fasterxml.jackson.core/jackson-core "2.10.2"]
[com.fasterxml.jackson.core/jackson-databind "2.10.2"]

• Look at the dependency tree and see which library is bringing in the wrong version of jackson-core and use :exclusions to prevent it from happening.

Writing raw values

Already encoded JSON values can be used with RawValue marker class:

(import '[com.fasterxml.jackson.databind.util RawValue])
(json/write-value-as-string
  {:version 555
   :foobar (RawValue. "{\"foo\": \"bar\"}")})