Cannot serialize or deserialize Maps with complex keys

import java.util.HashMap;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;


public class GsonTest {

    public static void main(String[] args) {

        new GsonTest();

    }

    public GsonTest() {
        HashMap<ComplexKey, String> map = new HashMap<ComplexKey, String>();

        map.put(new ComplexKey("Test1", "Test2"), "Value1");

        Gson gson = new Gson();
        System.out.println(gson.toJson(map, new TypeToken<HashMap<ComplexKey,
String>>(){}.getType()));
    }

    public class ComplexKey {

        private String keyOne;
        private String keyTwo;

        public ComplexKey(String keyOne, String keyTwo) {
            this.keyOne = keyOne;
            this.keyTwo = keyTwo;
        }

        public String getKeyOne() {
            return keyOne;
        }

        public void setKeyOne(String keyOne) {
            this.keyOne = keyOne;
        }

        public String getKeyTwo() {
            return keyTwo;
        }

        public void setKeyTwo(String keyTwo) {
            this.keyTwo = keyTwo;
        }
    }
}

Expected Output:
{"{"keyOne":"Test1","keyTwo":"Test2"}":"Value1"}


Actual Output:
{"GsonTest$ComplexKey@1172e08":"Value1"}

Original issue reported on code.google.com by [e-mail] on 25 May 2010 at 2:53

[GoogleCodeExporter]

For any internet travelers from the future (like myself)... you can enable this 
functionality in GSON 2.* with the enableComplexMapKeySerialization() method on 
GsonBuilder.

Original comment by [e-mail] on 9 Jan 2013 at 8:29

[electronicpeter]

enableComplexMapKeySerialization() is a great help and should be default. Thanx for the hint!