Add TypeHierarchyAdapters?

[DanielGronau]

When a class contains a field with a vavr interface type, e.g. Map, Gson can't deserialize it, as it needs a certain implementation of Map. Often a particular implementation (like HashMap) would be a good default for the majority of classes, so one could just register a TypeHierarchyAdapter using a HashMap to deserialize a Map field. Such TypeHierarchyAdapters could be part of the library (but not registered in VavrGson, just as additional helpers).

[ruslansennov]

PRs Welcome!

[mincong-h]

Hi @DanielGronau and @ruslansennov , I would like to help on this issue. I created a simple test case trying to reproduce, but the test passed. So both serialization and deserialization works.

package io.vavr.gson.map;

import io.vavr.collection.HashMap;
import io.vavr.collection.Map;
import io.vavr.gson.AbstractTest;
import org.junit.Test;

public class MapInObjectTest extends AbstractTest {
    @Test
    public void testTypeHierarchyAdapters() {
        Foo foo = gson.fromJson("{\"config\":{\"k\":1}}", Foo.class);
        assert foo.config.equals(HashMap.of("k", 1));
        assert gson.toJson(foo).equals("{\"config\":{\"k\":1}}");
    }

    private static class Foo {
        private Map<String, Integer> config;

        Foo() {
            // no-args constructor
        }
    }
}

Am I doing something wrong?