CODEWITHSUNDEEP
javagsonoutputstream
Suzan Cioc
Suzan Cioc

Reputation: 30137

Gson bug? PrettyPrinting is ignored if writing to file

How to use pretty printing when writing to file?

package tests;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.stream.JsonWriter;

public class Try06 {

    public static class V {
        double x, y;
    }


    public static void main(String[] args) throws IOException {

        GsonBuilder gb = new GsonBuilder();

        gb = gb
         .setPrettyPrinting()
         .setVersion(1.0)


         ;

        Gson gson0 = gb.create();

        File file = new File("D:\\test.json");

        System.out.println(gson0.toJson(new V()));

        JsonWriter writer = new JsonWriter(new OutputStreamWriter(new FileOutputStream(file)));
        gson0.toJson(new V(), V.class, writer);
        writer.flush();
        writer.close();



    }
}

Also I noticed, that file is empty if not flushed. Should it flushed when exit?

Upvotes: 0

Views: 1442

Answers (2)

Ilya Shinkarenko
Ilya Shinkarenko

Reputation: 2182

Explicitly setting a non-empty String indent helps:

Gson gson = new GsonBuilder().setPrettyPrinting().create();
JsonWriter writer = new JsonWriter(new FileWriter(fileOut));
writer.setIndent("  "); // <-- without this the file is written without line-breaks and indents
gson.toJson(object, type, writer);

Have not had time to check Gson source, probably there's another way to solve it.

Upvotes: 2

DmitryKanunnikoff
DmitryKanunnikoff

Reputation: 2266

private void newline() throws IOException {
    if (indent == null)
        return;

    out.write("\n");   //--- Your problem here!

    int i = 1;
    for (int size = stackSize; i < size; i++)
        out.write(indent);
}

This part of the source of JsonWriter class. As a string delimiter is used '\n'. It is suitable for UNIX systems. But Windows is used for a new line '\r\n'.

How to solve your problem? Look at this:

DataOutputStream dos = new DataOutputStream(new FileOutputStream(file));
dos.writeBytes(gson0.toJson(new V()).replace("\n", "\r\n"));
dos.flush();
dos.close();

If you want system independed solution, then replace "\r\n" by this:

System.getProperty("line.separator");

or by this:

System.lineSeparator();

Upvotes: 0

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