Hey,
May somebody please have a look at the following problem?
It is about nested polymorphism into another object and it fails on
nullPointerException when it meets attribute using abstract class
declaration.
In other words it fails to determine which concrete entity to use when
parent entity for that attribute is using abstract entity.Or it never does
- since it never enter the deserializer.
Problem:
1) I am acting as a proxy, getting requests from UI and forwarding them to
the other system.
2) Before sending the response back to the UI I am mapping it to my local
DTO schema of that remote system – so we can have power over what we send
to the UI..
3) That system sends completely ambiguous data structure depending on their
count. Imagine entity object with attribute member. If that member is only
one, that attribute is object. If more than one, then that attribute is
array.
So you see my point now.. I have 2 DTOs for this case – 1 is when member is
object, 2 is when member is array and they both inherit from abstract
parent.
But this isnt all.. That schema I just described is wrapped into another
Wrapper object where I am using their abstract parent for the attribute
type. That wrapper is needed because that remote system returns 0 or 1 or
>1 objects in the very same attribute of that wrapper but of different type
also. So it looks like this:
public class Wrapper {
@JsonProperty(“wrapper”)
private AbstractWrapper wrapper;
}
public abstract class AbstractWrapper {
}
public class WrapperString extends AbstractWrapper {
@JsonProperty(“dto”)
private String dto;
}
public class WrapperObject extends AbstractWrapper{
@JsonProperty(“dto”)
private AbstractDTO dto;
}
public class WrapperList extends AbstractWrapper{
@JsonProperty(“dto”)
private List<AbstractDTO> dto;
}
public abstract class AbstractDTO {
}
public class Impl1DTO extends AbstractDTO {
@JsonProperty(“member”)
private String member;
}
public class Impl2DTO extends AbstractDTO {
@JsonProperty(“member”)
private List<String> member;
}
I have both deserializers for this registered. It will check if member is
type of Object or Array or String and determine the concrete class. This
works for the Wrapper Polymorphism. However it doesnt for nested
polymorphism. It never enters that deserializer no matter what I try.. And
when deserializing it fails on null pointer exception on @JsonProperty(“dto
”)
Here is also more detailed stackoverflow
<https://stackoverflow.com/questions/51309359/jackson-deserialization-with-polymorphism-nested-into-polymorphism-aka-more-th>
thread
I created for this.
I will appreciate any inputs for this. Thanks, Michal
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