Unexpected token END OF FILE at position 0 while parsing JSON

Question

In order to find out weather the JSON element is JSONArray or JSONObject type, I am getting Unexpected token END OF FILE at position 0 error.

My JSON is:

{"colors":[{"color":"red","value":"#00"},{"color":"white","value":"#000g"}]}

My code is:

java.io.FileReader reader = new java.io.FileReader("jsonpath");
org.json.simple.parser.JSONParser parser = new JSONParser();
System.Out.Println("aaaaaa JSON Class: "+parser.parse(reader).getClass());
if(parser.parse(reader) instanceof org.json.simple.JSONArray)
    System.Out.Println("JSONArray");
else if(parser.parse(reader) instanceof org.json.simple.JSONObject)
    System.Out.Println("JSONObject");

When I run above code it shows this output

aaaaaa JSON Class: class org.json.simple.JSONObject Unexpected token END OF FILE at popsition 0
at org.json.simple.parser.JSONParser(Unknown Source)
.
.
.
<rest of the exception>

I don't understand why this exception is occurring. Please help me out.

Some more details after edit:

My this code is working fine with the given json file:

java.io.FileReader reader = new java.io.FileReader("jsonpath");
org.json.simple.parser.JSONParser parser = new JSONParser();
org.json.simple.JSONObject object = (JSONObject)parser.parse(reader);
System.Out.Println("JSONObject: "+object);
org.json.simple.JSONArray array = (JSONArray)object.get("colors");
System.Out.Println("JSONArray: "+array);

Output of above code:

JSONObject: {"colors":[{"color":"red","value":"#00"},{"color":"white","value":"#000g"}]}
JSONArray: [{"color":"red","value":"#00"},{"color":"white","value":"#000g"}]

But I want to dynamically parse the JSON without knowing the JSON structure. I want to do something like this:

  if(json is object)
    JSONObject object = (JSONObject)parser.parse(reader);
  else if (json is array)
    JSONArray array = (JSONArray)parser.parse(reader);

Thanks.

Answer 1

You're repeatedly parsing the same Reader. The first call exhausts it and then each subsequent call sees an empty stream.

Answer 2

Parse the reader only once. Here is the working code:

java.io.FileReader reader = new java.io.FileReader("jsonpath");
org.json.simple.parser.JSONParser parser = new JSONParser();
Object p = parser.parse(reader);
if(p instanceof org.json.simple.JSONArray){
    System.Out.Println("JSONArray");
    org.json.simple.JSONArray object = (JSONArray)p;
}
else if(p instanceof org.json.simple.JSONObject){
    System.Out.Println("JSONObject");
    org.json.simple.JSONObject object = (JSONObject)p;
}

Output of above code

JSONObject

Answer 3

Well, error may occur when you try to pass wrong path.

So check your path to json file properly. Try to use absolute path at first.

Here is my procedure:

private static void ReadWithEncoding(String filePath, String encoding) {
    StringBuilder json = new StringBuilder();
    File f = new File(filePath);
    if (f.exists() && f.isFile()) {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(f), encoding));
            String line;
            while ((line = br.readLine()) != null) {
                json.append(line);
            }
            br.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(json);
    }
}

You may run it like this for UTF8:

ReadWithEncoding("D:/file.json", "UTF8");

For Cyrillic symbols:

ReadWithEncoding("D:/file.json", "Cp1251");