Converting Nested Json files to CSV in java

Question

    {
    "Employee": [
        {
            "empMID": "mock:1",
            "comments": [],
            "col1": "something",
            "contact": [{"address":"2400 waterview", "freetext":true}
                         ],
            "gender": "male"
        },
        {
            "empMID": "mock:2",
            "comments": [],
            "col1": "something",
            "contact": [{"address":"2200 waterview", "freetext":true}
                         ],
            "gender": "female"
        }
    ],
    "cola": false,
    "colb": false
}

This is how my Json file looks .I m required to convert this json to a csv .(I m trying to convert a multi-dimesional data to 2d).I m using gson for my purpose.I cannot use gson.fromgson() function to object map with a template because it should be generic .

I know we can use CDL to convert jsonarray to csv format but It wont work in my case .

my csv format looks like

Employee*
empMID,comment.$,contact.address,contact.freetext,gender
mock:1,,2400 waterview,TRUE,male
mock:123,,2200 waterview,TRUE,female
colA#
TRUE
colB#
FALSE

I tried using google-GSON api to convert to this format .But I m not able to convert to this format .I have used * to represent its a json array and # to represent its a primitive type and contact.address to represent nested array inside another json array .I having problem relating this nested structure .I m able to traverse everything recursively like a column. Thanks in advance

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

        BufferedReader reader=null;
        StringBuilder content=null;
        String result=null;

            reader = new BufferedReader(new FileReader("temp.json"));

            String line = null;
            content= new StringBuilder();

            while ((line = reader.readLine()) != null) {
            content.append(line);
            }
            reader.close();
            result= content.toString();

            JsonElement jelement = new JsonParser().parse(result);

            printJsonRecursive(jelement);


        }


    public static void printJsonRecursive(JsonElement jelement){


        if(jelement.isJsonPrimitive()){

            System.out.println(jelement.getAsString());
            return;
        }
        if(jelement.isJsonArray()){

            JsonArray jarray= jelement.getAsJsonArray();
            for(int i=0;i<jarray.size();i++){
                JsonElement element= jarray.get(i);
                printJsonRecursive(element);
            }
            return;

        }
        JsonObject  jobject= jelement.getAsJsonObject();

        Set<Entry<String, JsonElement>> set= jobject.entrySet();

        for (Entry<String, JsonElement> s : set) {

            printJsonRecursive(s.getValue());


        }

    }



}

Answer 1

You can achieve this thru reflection if you have a object mapped to the json.

1. use gson/jackson to convert json to java object

2. append fields using reflection by iterating the class and get any field you interested in.

3. append value with reflection by getting value from the target object.

More detail look at my blog post below:

vcfvct.wordpress.com/2015/06/30/converting-nested-json-files-to-csv-in-java-with-reflection/