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My main goal is to get the information out of a JSON file and manipulate it in memory (trying to solve syntax issues in memory). Afterward, parse the manipulated value into an Object with com.google.gson.JsonParser and leave the old File as it was in the beginning (with the syntax errors included).

I managed to manipulate the File with RandomAccessFile and Parse it afterward while using "new FileReader". But after running through the code I noticed that the "old" file was modified and that shouldn't be the case. I don't want to change the file itself but the content and parse it into an Object with JsonParser or whatever Parser there is available for this.

import com.google.gson.JsonArray;
import com.google.gson.JsonParser;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.RandomAccessFile;

public class JsonLoggingParser {


    public static final void main(String[] args) {
        String path = "C:\\CEC\\Dev\\logs\\BIMBO\\2019-04-12asdf.json";

        parseJsonLogFile(path);
    }



    public static void parseJsonLogFile(String filePath){
        try {

            File f = new File(filePath);


            RandomAccessFile randomAccessFile = new RandomAccessFile(f, "rw");

            randomAccessFile.seek(0);
            randomAccessFile.write("[{".getBytes());
            randomAccessFile.seek(f.length());
            randomAccessFile.write("]".getBytes());
            randomAccessFile.close();

            JsonParser jsonParser = new JsonParser();

            Object object = jsonParser.parse(new FileReader(f));

            JsonArray jsonArray = (JsonArray)object;


            System.out.println(jsonArray.toString());

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

This is how my JSON file looks like:

{
  "788ad1bc-e9c8-4be5-b5b6-26ba011dc40e-request": {
    "date": "2019-04-15 10:28:58.943",
    "url": "/BIMBO/credit",
    "handleType": "request",
    "status": "200",
    "request": "Hello There",
    "response": "",
    "performanceDuration": "",
    "principalID": "123456789"
  }
},{
  "788ad1bc-e9c8-4be5-b5b6-26ba011dc40e-response": {
    "date": "2019-04-15 10:28:59.125",
    "url": "/BIMBO/credit",
    "handleType": "response",
    "status": "422",
    "request": "",
    "response": "Hello Back",
    "performanceDuration": "218.696979ms",
    "principalID": ""
  }
}

Basically I need to add a "[" and "]" at the beginning/end of the file to solve the syntax issue.

Luca Archidiacono
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  • Maybe look into Gson, its a api for Json https://github.com/google/gson – Starmixcraft Apr 16 '19 at 07:56
  • I guess when the file has some syntax errors Gson won't help me that much, that's why I have to manipulate it beforehand. – Luca Archidiacono Apr 16 '19 at 08:02
  • Gson can handel malformed json, there is a option in the builder – Starmixcraft Apr 16 '19 at 08:03
  • I saw there is a option called setLenient. But if I set this option Gson will automatically only read the first Json Object. And with my syntax correction I want to have multiple objects in 1 array. That's why I add "[" and "]" at the beginning/end of the file. – Luca Archidiacono Apr 16 '19 at 08:21

1 Answers1

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The json is not melformed in any way, its just a map like Map<String, Objekt> a TypeToken might help solve youre problem:

gson.fromJson(reader, new TypeToken<HashMap<String, class>>() {}.getType());

if you have a fileWriter it will overright data

example data:

Hello world

if you write a K at 0 it will look like this

Kello world

Starmixcraft
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  • Thanks for your help. I tried as you suggested but if I set lenient to "true" and use TypeToken I get only one object of two inside the Map. And if I disable lenient I get a malformedException. – Luca Archidiacono Apr 16 '19 at 08:42
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    If that also dosent work, im out of ideas, the best thing you can do is load the json to ram, place youre [ ] and then pars it, as this post tells https://stackoverflow.com/questions/2537944/prepend-lines-to-file-in-java, no filesystem supports appending chars to a file, so loading it to ram is the best way to do it – Starmixcraft Apr 16 '19 at 08:46
  • Ok I'll take a look into it. Thanks anyways for your time and effort :) – Luca Archidiacono Apr 16 '19 at 08:48