in cloud-spanner-r2dbc/src/main/java/com/google/cloud/spanner/r2dbc/v2/ClientLibraryDecoder.java [117:133]
static Class<?> getDefaultJavaType(Type spannerType) {
switch (spannerType.getCode()) {
case BOOL: return Boolean.class;
case INT64: return Long.class;
case FLOAT64: return Double.class;
case STRING: return String.class;
case BYTES: return ByteBuffer.class;
case TIMESTAMP: return LocalDateTime.class;
case DATE: return LocalDate.class;
case NUMERIC: return BigDecimal.class;
case ARRAY: return Array.newInstance(getDefaultJavaType(spannerType.getArrayElementType()), 0)
.getClass();
case JSON: return JsonWrapper.class;
default:
return Object.class;
}
}