从服务器上的文件解析 json

Question

I am working on an android project that parses JSON from a file on a server and converting the data into java objects to display the data using text views.

I have created a HTTP connection so that the app can make a GET request to the server to retrieve the contents of the file. I also have a method to convert JSON to string and display the JSON in the logcat, so that I know the GET request was successful.

I pass a string that holds the url to the server and use my HttpHandler to make the connection.

private class parseJSON extends AsyncTask<Void, Void, List<Book>> {

    private final String TAG = parseJSON.class.getSimpleName();
    @Override
    protected List<Book> doInBackground(Void... voids) {
        Log.i(TAG, "Start Async to get books.");
        ArrayList<Book> bookArray = new ArrayList<>(0);

        String jsonUrl = getApplication().getString(R.string.json_feed);
        HttpHandler httpHandler = new HttpHandler();
        String jsonString = httpHandler.makeJsonServiceCall(jsonUrl);

        Log.i(TAG, "Response from url: " + jsonString);

        if( jsonString != null) {
            try {
                JSONObject jsonObject = new JSONObject(jsonString);

                // Get JSON array node.
                JSONArray jArray = jsonObject.getJSONArray("book");

                // Looping through all the books.
                for (int i = 0; i < jArray.length(); i++) {
                    JSONObject jsonEntry = jArray.getJSONObject(i);

                    String year = jsonEntry.getString("year");
                    String title = jsonEntry.getString("title");
                    String publisher = jsonEntry.getString("publisher");
                    String price = "£" + jsonEntry.getString("price");

                    final Book bookObject = new Book(year, title, publisher, price);

                    //Add the new books to our result array.
                    bookArray.add(bookObject);
                }

            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
        return bookArray;
    }

    @Override
    protected void onPostExecute( List<Book> books) {
        super.onPostExecute(books);
        Log.e(TAG, "Populate UI recycler view with json converted data.");
       // bookArray
        bookList.setValue(books);
    }
}

The parsing seems to get interrupted when I try to get the array node.

The following issues arise:

org.json.JSONException: Value "Contents of my json file"

at org.json.JSON.typeMismatch(JSON.java:101)

at org.json.JSONObject.getJSONArray(JSONObject.java:591)

Then refers to a line 170 which is:

 // Get JSON array node.
 JSONArray jArray = jsonObject.getJSONArray("book");

Could I be doing something wrong with the parsing process?

Answer 1

Nothing wrong with your parsing, but your JSONPath is bad. Look at your original structure. The actual path is $.bib.book , so to get that array, you need to do

new JSONObject(jsonString).getJSONObject("bib").getJSONArray("book")

You may be able to do .getJSONArray("bib.book") but I'm not sure how that class parses JSON and if nested paths are supported.