Add custom indent for pretty printing

[WasylF]

It would be great if we can specify custom indent while call pretty printing. Currently pretty printing always use 2 spaces for indent. This customization also allows to reduce size of resulting json.
Comparison table and code for generating json below:

Indent \ setsCount	100	2000
2 spaces	99,7 kb	50,9 MB
1 tab	79,5 kb	42,9 MB
nothing	59,3 kb	34,9 MB

        List<Set<Integer>> sets = new ArrayList<Set<Integer>>();
        int setsCount = 2000;
        for (int setN = 0; setN < setsCount; setN++) {
            TreeSet<Integer> set = new TreeSet<Integer>();
            for (int i = 0; i < setsCount; i++) {
                set.add(setN * setsCount + i);
            }
            sets.add(set);
        }

        String json = gsonManager.getGson().toJson(sets);

[JakeWharton]

What's the motivation? If you care about size you aren't using pretty printing.

[WasylF]

My team's project stores some large configuration data in the git repository as JSON. If I don't use pretty option the resulting file contains a single line with the whole JSON, so git couldn't show a difference between different versions. Currently, I use pretty JSON, but in my case, it increases the size of the JSON from 30 - 40 MB up to 100+ MB. Bigger resulting JSON also requires more RAM for converting. So, I suppose it would be cool to have such feature as a custom indent.
And the other reason is that war between people using tabs and spaces is endless:) So, it is great to have both options.

[bonoboris]

I agree, if you are appending to an existing Json with either 2, 4 spaces or tab indent, it would be nice to have such a feature. I'm actually suprised there isn't.

[yurymann]

+1 for configurable indent size

@JakeWharton , my motivation is being able to compare jsons generated with gson against json files formatted in other tools, in my case IntelliJ Idea.

[nickgeorge]

+1 for configurability!

[Conrad-T-Pino]

Already implemented in 2.8.7 release.

Class com.google.gson.stream.JsonWriter has public final void setIndent​(String indent); which:

Sets the indentation string to be repeated for each level of indentation in the encoded document. If indent.isEmpty() the encoded document will be compact. Otherwise the encoded document will be more human-readable.

This implementation indents with tab and appends final newline:

void run(final File file, final JsonElement element) {
	final Gson gsonPrettyPrinting = new GsonBuilder().setPrettyPrinting().create();
	try (final PrintWriter pWriter = new PrintWriter(file)) {
		final JsonWriter jWriter = gsonPrettyPrinting.newJsonWriter(pWriter);
		jWriter.setIndent("\t");
		gsonPrettyPrinting.toJson(element, jWriter);
		pWriter.println();
	} catch (final IOException e) {
	}
}

Best regards!

[eamonnmcmanus]

I believe @Conrad-T-Pino is right that this feature has been implemented, so the issue can be closed.

[Conrad-T-Pino]

Untested JasonElement to String case:

String run(final JsonElement element) {
	final Gson gsonPrettyPrinting = new GsonBuilder().setPrettyPrinting().create();
	try (final StringWriter sWriter = new StringWriter(file)) {
		final JsonWriter jWriter = gsonPrettyPrinting.newJsonWriter(sWriter);
		jWriter.setIndent("\t");
		gsonPrettyPrinting.toJson(element, jWriter);
		sWriter.write(System.lineSeparator());
		return sWriter.toString();
	} catch (final IOException e) {
		return null;
	}
}

Best regards.

[xresch]

I use the pretty print for debug purposes to be able to actually read the JSON.
I think it is interesting that we cannot just pass the separator to the method as a parameter.
Here is the code I use for DEBUG PURPOSES ONLY.
I just replace any occurence of two blanks with a tab.

public static String toJSONPretty(Object object) {
    return gsonInstancePretty.toJson(object).replaceAll("  ", "\t");
}