Why is Spring Data MongoDB unable to instantiate this nested type structure?

Question

My document structure is like:

{
    _id: \"A\",
    groups:[{
        groupId: \"someId\",
        groupName: \"someName\",
        params: {
            type1:         


        

Answer 1

Failed to instantiate ... using constructor public ... ReflectionEntityInstantiator

says it cannot create the objects using reflection.

Do you have getters and setters for all the fields in all your classes? Your code above does not have them for ParamData, Config and DataConfig.

Also, if you happen to have non-default constructors in any of your classes make sure you have an empty argument constructor, else reflection will fail.