@Test
    public void deserializeNullToDefault() {
        converter.configure(Collections.singletonMap(JsonConverterConfig.REPLACE_NULL_WITH_DEFAULT_CONFIG, true), false);
        String value = "{\"schema\":{\"type\":\"string\",\"optional\":true,\"default\":\"default\"},\"payload\":null}";
        SchemaAndValue sav = converter.toConnectData(TOPIC, null, value.getBytes());
        assertEquals("default", sav.value());
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java