How to add custom Classloader to ObjectMapper? - json

Question

Is there any way to instruct Jackson 2 ObjectMapper to use custom Classloader to deserialize JSON strings?

Answer 1

Here is the solution:
ClassLoader myClassLoader = ...
ObjectMapper om = new ObjectMapper();
TypeFactory tf = TypeFactory.defaultInstance()
.withClassLoader(myClassLoader);
om.setTypeFactory(tf);

Answer 2

Take a look at the Jackson Wiki for Modules, a Jackson Module can be used to create custom serialization / deserialization. While the wiki talks about what they can do
Add custom serializers and deserializers
Add mix-in annotations
Override or add AnnotationIntrospector
Access SerializationConfig and DeserializationConfig settings.
It is pretty light on details, just giving a very basic example. The Module JavaDoc is light on details as well. Fortunately the wiki also has a list of existing Jackson Modules on GitHub, which is more helpful as examples if you need to create your own Module from scratch.

Answer 3

To preserve the existing TypeMapper, you might want to do something like this (this is Scala, but same pattern works in Java), where you adjust the current type factory.
def updateClassLoader(cl: ClassLoader): Unit = {
objectMapper.setTypeFactory(objectMapper.getTypeFactory.withClassLoader(cl))
}
This will preserve cached type data from possible prior configuration calls like this:
mapper.registerModule(new Jdk8Module)
.registerModule(new JavaTimeModule)
.registerModule(new DefaultScalaModule)