Generic type instantiation using reflection

Question

Assuming the following data model:

public Test extends CanDeserialize { private List<String> userRoles; ... }

When requiring to deserialize the object manually and having to instantiate an object for the userRole, the following problems happen:

Java reflection recognizes List<String> as List when calling the .GetType() method
When calling .GetGenericType() method, the actual type of T cannot be instantiated, as the method does not provide any function for that purpose.
Extracting the type from inside the <> and instantiating through Class.fromClass(...) may cause problems as the generic type maybe very complex, for example Pair<Pair<String,int>, Pair<String,int>>

Assuming that deserialization takes place inside of the class as follows:

public abstract CanDeserialize{ public void deserialize(String object){ Field[] fields = this.getClass().getDeclaredFields(); }

How can I instantiate an object for the userRoles??

Didn't you just ask this same question about 2 hours ago? Or am I confused? — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Jan 14, 2017 at 22:14
@HovercraftFullOfEels: You are surly confused :D (no disrespect :) ) — Arnold Zahrneinder
– Arnold Zahrneinder, Commented Jan 14, 2017 at 22:16

Transcendent · Accepted Answer · 2017-01-14 22:39:26Z

In Java you can do the following:

List list = new ArrayList(); list.add("Some Values");

Now assuming you have a List<String> you can set value using reflection through getting fields (as you did) and then

fields[0].set(this, list); // in your example there's 1 field only, so the index is 0.

This works because in Java, any generics eventually lead to Object type. And yeah that means you don't need reflection to initialize that.

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