如何用Java将表数据写入JSON文件？

Question

I'm trying to write all table data into a JSON file using Java in a particular format. I like to get the JSON file written in the following format:

 [{
    "com_name": "Google",
    "com_code": 12,
    "IT": [{
        "type_3": "Hero",
        "type_2": "To",
        "type_1": "Zero",
        "cat_no": "AC06",
        "cat_desc": "CareWorld"
    }, {
        "type_3": "Hero",
        "type_2": "To",
        "type_1": "Zero",
        "cat_no": "AC06",
        "cat_desc": "CareWorld"
    }],
    "SALES": [{
        "type_3": "",
        "type_2": "",
        "type_1": "",
        "cat_no": "SL01",
        "cat_desc": "SellBetter"
    }],
    "MARKETING": [{
        "type_3": "OK",
        "type_2": "OK",
        "type_1": "AZC",
        "cat_no": "M1",
        "cat_desc": "Required"
    }]
 }, {
    "com_name": "Microsoft",
    "com_code": 18,
    "PRODUCT": [{
        "type_3": "INDIA",
        "type_2": "JAPAN",
        "type_1": "USA",
        "cat_no": "P01",
        "cat_desc": "Windows10"
    }]
 }, {
    "com_name": "StackOverflow",
    "com_code": 14,
    "IT": [{
        "type_3": "JS",
        "type_2": "JSON",
        "type_1": "Java",
        "cat_no": "QA",
        "cat_desc": "QuestionandAnswer"
    }],
    "SALES": [{
        "type_3": "",
        "type_2": "DONE",
        "type_1": "",
        "cat_no": "S1",
        "cat_desc": "internet"
    }]
 }]

I have tried it too many times and surfing the internet but unable to get required format. My code is perfectly writing table data into the JSON file.

I am fetching all data from the database table. Here is the snapshot of my dummy table.

Please check what's wrong with my Java code.

WriteJsonFile.java

        ResultSet res = stmt.executeQuery("SELECT com_name,com_code,dept,cat_no,cat_desc,type_1,type_2,type_3 FROM json_data");
        JSONArray jsonArray = new JsonConverter().convertToJSON(res);
        FileWriter fileWriter = new FileWriter("json_file.json");
        JSONObject obj = null;
        fileWriter.write("[");
        for (int i = 0; i < jsonArray.length(); i++) {
            obj = (JSONObject) jsonArray.get(i);
            if (i != jsonArray.length() - 1) {
                fileWriter.write(obj.toString() + ",\n");
            } else {
                fileWriter.write(obj.toString());
            }

        }
        fileWriter.write("]");
        fileWriter.flush();

And the code to convert ResultSet to JSON.

JsonConverter.java

public static JSONArray convertToJSON(ResultSet resultSet) throws Exception {
    JSONArray jsonArray = new JSONArray();
    while (resultSet.next()) {
        JSONObject obj = null;
        obj = new JSONObject();
        int total_rows = resultSet.getMetaData().getColumnCount();
        for (int i = 0; i < total_rows; i++) {
            obj.put(resultSet.getMetaData().getColumnLabel(i + 1).toLowerCase(), resultSet.getObject(i + 1) != null ? resultSet.getObject(i + 1) : "");
        }
        jsonArray.put(obj);     }

    return jsonArray;
}

To do this I have used the json.jar . And above code result is:

[{
    "type_3": "Hero",
    "type_2": "To",
    "type_1": "Zero",
    "cat_no": "AC06",
    "cat_desc": "CareWorld",
    "com_code": 12,
    "dept": "IT",
    "com_name": "Google"
 }, {
    "type_3": "Hero",
    "type_2": "To",
    "type_1": "Zero",
    "cat_no": "AC06",
    "cat_desc": "CareWorld",
    "com_code": 12,
    "dept": "IT",
    "com_name": "Google"
 }, {
    "type_3": "",
    "type_2": "",
    "type_1": "",
    "cat_no": "SL01",
    "cat_desc": "SellBetter",
    "com_code": 12,
    "dept": "SALES",
    "com_name": "Google"
 }, {
    "type_3": "OK",
    "type_2": "OK",
    "type_1": "AZC",
    "cat_no": "M1",
    "cat_desc": "Required",
    "com_code": 12,
    "dept": "MARKETING",
    "com_name": "Google"
 }, {
    "type_3": "JS",
    "type_2": "JSON",
    "type_1": "Java",
    "cat_no": "QA",
    "cat_desc": "QuestionandAnswer",
    "com_code": 14,
    "dept": "IT",
    "com_name": "StackOverflow"
 }, {
    "type_3": "INDIA",
    "type_2": "JAPAN",
    "type_1": "USA",
    "cat_no": "P01",
    "cat_desc": "Windows10",
    "com_code": 18,
    "dept": "PRODUCT",
    "com_name": "Microsoft"
 }, {
    "type_3": "",
    "type_2": "DONE",
    "type_1": "",
    "cat_no": "S1",
    "cat_desc": "internet",
    "com_code": 14,
    "dept": "SALES",
    "com_name": "StackOverflow"
 }]

Answer 1

I wouldn't mess with the string provided by the jsonArray implementation. Looks like you are handling some square brackets yourself... //import java.io.File; //import java.io.FileOutputStream;

private boolean writeFile(File file,String conts){
    try {
        file.createNewFile();
        FileOutputStream fOut = new FileOutputStream(file);
        OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
        myOutWriter.append(conts);
        myOutWriter.close();
        fOut.flush();
        fOut.close();
        return(true);
    }catch(IOException e){
        return(false);
    }
}
ResultSet res = stmt.executeQuery("SELECT com_name,com_code,dept,cat_no,cat_desc,type_1,type_2,type_3 FROM json_data");
JSONArray jsonArray = new JsonConverter().convertToJSON(res);
writeFile(new File(".json_file.json"),jsonArray.toString() )

Answer 2

You need to modify your 'SQL' query. Add the ORDEr BY clause to come to your data in the arranged way.

SQL:

SELECT com_name,com_code,dept,cat_no,cat_desc,type_1,type_2,type_3 FROM json_data order by com_name,dept;

And here the method to convert all table data to JSON.

public static JSONArray convert(ResultSet rs) {

    Set<String> nameSet = new HashSet<>();
    Set<String> deptSet = new HashSet<>();
    JSONArray jsonArray = new JSONArray();
    JSONArray jsonArray2 = null;
    JSONObject obj = null;
    JSONObject obj2 = null;
    try {
        while (rs.next()) {
            int total_rows = rs.getMetaData().getColumnCount();
            if (nameSet.contains(rs.getString(1))) {
                if (deptSet.contains(rs.getString(3))) {
                    obj2 = new JSONObject();
                    for (int j = 3; j < total_rows; j++) {
                        obj2.put(rs.getMetaData().getColumnLabel(j + 1).toLowerCase(),
                                rs.getObject(j + 1) != null ? rs.getObject(j + 1) : "");
                    }
                    jsonArray2.put(obj2);
                } else {
                    obj2 = new JSONObject();
                    jsonArray2 = new JSONArray();
                    deptSet.add(rs.getString(3));
                    for (int j = 3; j < total_rows; j++) {
                        obj2.put(rs.getMetaData().getColumnLabel(j + 1).toLowerCase(),
                                rs.getObject(j + 1) != null ? rs.getObject(j + 1) : "");
                    }
                    jsonArray2.put(obj2);
                    obj.put(rs.getString(3), jsonArray2);
                }

            } else {
                if (obj != null) {
                    jsonArray.put(obj);
                }
                deptSet.removeAll(deptSet);
                obj = new JSONObject();
                obj2 = new JSONObject();
                jsonArray2 = new JSONArray();
                nameSet.add(rs.getString(1));
                for (int i = 0; i < 2; i++) {
                    obj.put(rs.getMetaData().getColumnLabel(i + 1).toLowerCase(),
                            rs.getObject(i + 1) != null ? rs.getObject(i + 1) : "");
                }
                if (deptSet.contains(rs.getString(3))) {

                } else {
                    deptSet.add(rs.getString(3));
                    for (int j = 3; j < total_rows; j++) {
                        obj2.put(rs.getMetaData().getColumnLabel(j + 1).toLowerCase(),
                                rs.getObject(j + 1) != null ? rs.getObject(j + 1) : "");
                    }
                }
                jsonArray2.put(obj2);
                obj.put(rs.getString(3), jsonArray2);
            }
        }
        jsonArray.put(obj);
    } catch (Exception e) {
        e.printStackTrace();
    }
    System.out.println("Final JSON: " + jsonArray);
    return jsonArray;
}

Generated JSON from the above code.

[
  {
    "MARKETING": [
      {
        "type_3": "OK",
        "type_2": "OK",
        "type_1": "AZC",
        "cat_no": "M1",
        "cat_desc": "Required"
      }
    ],
    "com_code": 12,
    "IT": [
      {
        "type_3": "",
        "type_2": "",
        "type_1": "a",
        "cat_no": "XYZ",
        "cat_desc": "World"
      },
      {
        "type_3": "",
        "type_2": "fine",
        "type_1": "Right",
        "cat_no": "ABC",
        "cat_desc": "People"
      }
    ],
    "SALES": [
      {
        "type_3": "",
        "type_2": "",
        "type_1": "",
        "cat_no": "SL01",
        "cat_desc": "Sell Better"
      }
    ],
    "com_name": "Google"
  },
  {
    "PRODUCT": [
      {
        "type_3": "INDIA",
        "type_2": "JAPAN",
        "type_1": "USA",
        "cat_no": "P01",
        "cat_desc": "Windows 10"
      }
    ],
    "com_code": 18,
    "com_name": "Microsoft"
  },
  {
    "com_code": 14,
    "IT": [
      {
        "type_3": "JS",
        "type_2": "JSON",
        "type_1": "Java",
        "cat_no": "QA",
        "cat_desc": "Question and Answer"
      }
    ],
    "SALES": [
      {
        "type_3": "",
        "type_2": "DONE",
        "type_1": "",
        "cat_no": "S1",
        "cat_desc": "internet"
      }
    ],
    "com_name": "StackOverflow"
  }
]

Hope it will help you :)