Jackson JSON Not Formatting Correctly

Question

I have data that looks like this:

{
    "status": "success",
    "data": {
        "irrelevant": {
            "serialNumber": "XYZ",
            "version": "4.6"
        },
        "data": {
            "lib": {
                "files": [
                    "data1",
                    "data2",
                    "data3",
                    "data4" 
                ],
                "another file": [
                    "file.jar",
                    "lib.jar" 
                ],
                "dirs": []
            },
            "jvm": {
                "maxHeap": 10,
                "maxPermSize": "12"
            },
            "serverId": "134",
            "version": "2.3"
        }
    }
}

Here is the function I'm using to prettify the JSON data:

public static String stringify(Object o, int space) {
    ObjectMapper mapper = new ObjectMapper();
    try {
        return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(o);
    } catch (Exception e) {
        return null;
    }
}

I am using the Jackson JSON Processor to format JSON data into a String. For some reason the JSON format is not in the format that I need. When passing the data to that function, the format I'm getting is this:

{
    "status": "success",
    "data": {
        "irrelevant": {
            "serialNumber": "XYZ",
            "version": "4.6"
        },
        "another data": {
            "lib": {
                "files": [ "data1", "data2", "data3", "data4" ],
                "another file": [ "file.jar", "lib.jar" ],
                "dirs": []
            },
            "jvm": {
                "maxHeap": 10,
                "maxPermSize": "12"
            },
            "serverId": "134",
            "version": "2.3"
        }
    }
}

As you can see under the "another data" object, the arrays are displayed as one whole line instead of a new line for each item in the array. I'm not sure how to modify my stringify function for it to format the JSON data correctly.

Answer 1

You should check how DefaultPrettyPrinter looks like. Really interesting in this class is the _arrayIndenter property. The default value for this property is FixedSpaceIndenter class. You should change it with Lf2SpacesIndenter class.

Your method should looks like this:

public static String stringify(Object o) {
    try {
        ObjectMapper mapper = new ObjectMapper();
        DefaultPrettyPrinter printer = new DefaultPrettyPrinter();
        printer.indentArraysWith(new Lf2SpacesIndenter());
        return mapper.writer(printer).writeValueAsString(o);
    } catch (Exception e) {
        return null;
    }
}