### Question:
JsonElementConverter implements Converter { @Override public Object toColumnValue(Object o) { return o == null ? null : o.toString(); }  @Override DataType getDataType(); @Override Class<?> getValueType(); @Override Object toColumnValue(Object o); @Override Object toFacetValue(Object o);  }### Answer:
@Test public void testToColumnValue() { JsonElementConverter converter = new JsonElementConverter(); assertNull(converter.toColumnValue(null)); assertEquals("null", converter.toColumnValue(JsonNull.INSTANCE)); assertEquals("\"hello\"", converter.toColumnValue(new JsonPrimitive("hello"))); assertEquals("1", converter.toColumnValue(new JsonPrimitive(1))); assertEquals("false", converter.toColumnValue(new JsonPrimitive(false))); assertEquals("[1,2,3]", converter.toColumnValue(array)); assertEquals(object.toString(), converter.toColumnValue(object)); }