Java: How to create a new instance from a TypeReference object?

Question

I have a method that accepts a com.fasterxml.jackson.core.type.TypeReference and returns an object of the referenced type, but in a certain case I want to just return a new instance of that type.

Example:

public <T> T getProperty(String property, TypeReference<T> typeReference) {
    try {
        return someInstanceOfReferencedType();
    }
    catch (IOException e) {
        return ???;
    }
}

How can I instantiate <T> using typeReference? I can get the Type from it, but not sure what to do from there...

Take a look at http://stackoverflow.com/questions/1090458/instantiating-a-generic-class-in-java — Anubhab, Dec 11 '14 at 06:14
Using a TypeReference because it may be, for example, a `Map` type and I want to retain that. — Shaun Scovil, Dec 11 '14 at 06:19
I see what you mean. I guess I should just throw an exception in this case. — Shaun Scovil, Dec 11 '14 at 06:30
Not necessarily. Some libraries choose to have default implementations. Note that a `HashMap` is the same as a `HashMap` at the time you instantiate it. Jackson needs the type reference in order to know how to deserialize nested JSON elements. If you're not doing that, I don't see you needing the type reference. — Sotirios Delimanolis, Dec 11 '14 at 15:22

score -1 · Answer 1 · edited May 30 '18 at 09:30

-1

You can create an instance of TypeReference as:

List<String> l1 = new TypeReference<ArrayList<String>>() {}.newInstance();

So you can call getProperty method as:

List<String> list = getProperty("property1",new TypeReference <>(){});
//Specify List<> in <> of TypeReference.

edited May 30 '18 at 09:30

CodeF0x

2,624
6
17
28

answered May 30 '18 at 08:10

anand kadu

68
4

Java: How to create a new instance from a TypeReference object?

1 Answers1