Why will Gson pretty-print to the console, but not the file?

Question

I have a class, let\'s call it Cls, with some values in it. When I use a Gson instance declared with GsonBuilder.setPrettyPrinting().create() and use that to se

Answer 1

Presumably, you're using something like this

Gson gson = new GsonBuilder().setPrettyPrinting().create();

try (FileWriter fileWriter = ...) {
    gson.toJson(new Example(), Example.class, new JsonWriter(fileWriter));
}

The JsonWriter wasn't created from the Gson object and is therefore not configured to pretty print. You can, instead, retrieve a JsonWriter instance from the Gson object with newJsonWriter

gson.toJson(new Example(), Example.class, gson.newJsonWriter(fileWriter));

which

Returns a new JSON writer configured for the settings on this Gson instance.

This instance will pretty-print.

You can also set the indent on your own instance

JsonWriter jsonWriter = new JsonWriter(fileWriter);
jsonWriter.setIndent("  ");
gson.toJson(new Example(), Example.class, jsonWriter);