Nested generic collections don't return jsonized values on toJson

+  private static class ClassWithDistinguishableFieldName {
+    private String distinguishableFieldName = "distinguishableFieldValue";
+  }
+
+  private static class ClassWithHashMapField {
+    private String a = "a";
+    private String b = "b";
+    HashMap<String, Object> c = new HashMap<String, Object>();
+
+    ClassWithHashMapField() {
+      c.put("someArray", Arrays.asList(new 
ClassWithDistinguishableFieldName()));
+    }
+  }



+    ClassWithHashMapField o = new ClassWithHashMapField();
+    String json = gson.toJson(o);

json:
  {"a":"a","b":"b","c":{"someArray":{}}}

expected:
  {"a":"a","b":"b","c":{"someArray":[{"distinguishableFieldName":"distinguishableFieldValue"}]}}


This issue was blocking a project I am working on; so I attached a patch with a 
test.

Original issue reported on code.google.com by [e-mail] on 28 Jun 2010 at 2:47

[GoogleCodeExporter]

Can this be a solution?

--------------------------------------------------------------------------------
-------------------------------
package com.github.gimmi.spikegson;

import com.google.gson.*;
import com.google.gson.reflect.TypeToken;
import org.junit.Test;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

import static org.junit.Assert.assertEquals;

public class StringTemplateBuilderTest {
    private static class CustomType {
        public String value = "a value";
    }

    @Test
    public void should_serialize_custom_type_in_map_with_type_token() {
        Map<String, Object> obj = new HashMap<String, Object>();
        obj.put("k1", new CustomType());

        Type type = new TypeToken<Map<String, Object>>() {
        }.getType();

        String actual = new Gson().toJson(obj, type).replace('"', '\'');

        assertEquals("{'k1':{}}", actual);

        actual = new GsonBuilder().registerTypeAdapter(Object.class, new JsonSerializer<Object>() {
            @Override
            public JsonElement serialize(Object src, Type typeOfSrc, JsonSerializationContext context) {
                return context.serialize(src);
            }
        }).create().toJson(obj, type).replace('"', '\'');

        assertEquals("{'k1':{'value':'a value'}}", actual);
    }
}
--------------------------------------------------------------------------------
-------------------------------

Original comment by gianmarco.gherardi on 13 Apr 2011 at 5:43

[GoogleCodeExporter]

Decision which accepted by developers, to use the "static information about the 
type of", generate extremely delusional behavior of Gson:

----
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import java.util.Arrays;
import java.util.List;

public class Test {
  public static void main(String args[]) {
    Result result = new Result();
    Gson gson = new GsonBuilder().setPrettyPrinting().create();
    gson.toJson(result, System.out);
  }

  interface Column {
  }

  static class ColumnImpl implements Column {
    private final String one;
    private final int two;  
    private final Boolean three;

    public ColumnImpl(String one, int two, Boolean three) {
      this.one = one;
      this.two = two;
      this.three = three;
    }
  }

  static class Result {
    private List<ColumnImpl> columnImpls = Arrays.asList(
      new ColumnImpl("one", 2, false), 
      new ColumnImpl("two", 4, true), 
      new ColumnImpl("three", 8, false));
    private List<Column> columns = (List)columnImpls;
  }
}
------


print:


------
{
  "columnImpls": [
    {
      "one": "one",
      "two": 2,
      "three": false
    },
    {
      "one": "two",
      "two": 4,
      "three": true
    },
    {
      "one": "three",
      "two": 8,
      "three": false
    }
  ],
  "columns": [
    {},
    {},
    {}
  ]
}
------

For what has been chosen such behavior?

Original comment by [e-mail] on 28 Jul 2011 at 11:30