I have spent days on this. I have looked at a million different posts from other people having similar issues and tried tons of different things, but I cannot get my json file read in to my program.
It is a school assignment. The demo was for a media library which read in an example music.json file and displayed the tracks in a JTree. Our first assignment was to convert the generic media library to a music specific library, add Track and Album classes, and get search results from last.fm when an album and artist was searched through the app and display the results in the JTree.
I managed to make my Album and Track classes, read in the last.fm json and convert it to an Album Object. I then rewrote that Album object to a new album.json file. I have since started working on reading that json file back in to the MusicLibrary class so that it can display the results in the JTree. That is where I am running into trouble. I have to do some converting because the given music.json is meant for organizing by tracks (before there was an Album class), and now I need it to work off of the new Album class (which contains a Vector of Track objects).
I cannot use any tools that need maven or downloaded jar's to work (so no GSON, etc.). I have to use org.json methods only. The instructor's original code read the music.json into a HashTable. I have tried reading it into that, into a Vector, and into a HashMap. Nothing works. I keep getting the error's:
Exception reading music library album.json: JSONObject["channel"] is not a JSONObject.
or
Exception reading music library album.json: JSONObject["album"] is not a JSONObject.
or no error but then when I try to print the table/map/vector, it is always empty. The first error is when I don't use the JSONTokener and use the commented-out line below it. I have no idea where it is coming up with "channel". That is nowhere in my code. Anyway, I am posting my relevant code below. If you see tons of commented-out lines, those are all different things I have tried and/or some of the instructor's original code (such as the HashTable lib).
album.json (which I put into a formatter and validator for better display)
{
"album": "Believe",
"albumTracks": [
{
"trackInfo": "Track Name: Believe\nArtist: Cher\nRank: 1\nDuration: 241\n\n",
"trackArtist": "Cher",
"trackRank": "1",
"trackDuration": "241",
"trackTitle": "Believe"
},
{
"trackInfo": "Track Name: The Power\nArtist: Cher\nRank: 2\nDuration: 236\n\n",
"trackArtist": "Cher",
"trackRank": "2",
"trackDuration": "236",
"trackTitle": "The Power"
},
{
"trackInfo": "Track Name: Runaway\nArtist: Cher\nRank: 3\nDuration: 286\n\n",
"trackArtist": "Cher",
"trackRank": "3",
"trackDuration": "286",
"trackTitle": "Runaway"
},
{
"trackInfo": "Track Name: All or Nothing\nArtist: Cher\nRank: 4\nDuration: 237\n\n",
"trackArtist": "Cher",
"trackRank": "4",
"trackDuration": "237",
"trackTitle": "All or Nothing"
},
{
"trackInfo": "Track Name: Strong Enough\nArtist: Cher\nRank: 5\nDuration: 223\n\n",
"trackArtist": "Cher",
"trackRank": "5",
"trackDuration": "223",
"trackTitle": "Strong Enough"
},
{
"trackInfo": "Track Name: Dov'e L'amore\nArtist: Cher\nRank: 6\nDuration: 258\n\n",
"trackArtist": "Cher",
"trackRank": "6",
"trackDuration": "258",
"trackTitle": "Dov'e L'amore"
},
{
"trackInfo": "Track Name: Takin' Back My Heart\nArtist: Cher\nRank: 7\nDuration: 272\n\n",
"trackArtist": "Cher",
"trackRank": "7",
"trackDuration": "272",
"trackTitle": "Takin' Back My Heart"
},
{
"trackInfo": "Track Name: Taxi Taxi\nArtist: Cher\nRank: 8\nDuration: 304\n\n",
"trackArtist": "Cher",
"trackRank": "8",
"trackDuration": "304",
"trackTitle": "Taxi Taxi"
},
{
"trackInfo": "Track Name: Love Is the Groove\nArtist: Cher\nRank: 9\nDuration: 271\n\n",
"trackArtist": "Cher",
"trackRank": "9",
"trackDuration": "271",
"trackTitle": "Love Is the Groove"
},
{
"trackInfo": "Track Name: We All Sleep Alone\nArtist: Cher\nRank: 10\nDuration: 233\n\n",
"trackArtist": "Cher",
"trackRank": "10",
"trackDuration": "233",
"trackTitle": "We All Sleep Alone"
}
],
"albumArtist": "Cher",
"albumSummary": "Believe is the twenty-third studio album by American singer-actress Cher, released on November 10, 1998 by Warner Bros. Records. The RIAA certified it Quadruple Platinum on December 23, 1999, recognizing four million shipments in the United States; Worldwide, the album has sold more than 20 million copies, making it the biggest-selling album of her career. In 1999 the album received three Grammy Awards nominations including \"Record of the Year\", \"Best Pop Album\" and winning \"Best Dance Recording\" for the single \"Believe\". <a href=\"http://www.last.fm/music/Cher/Believe\">Read more on Last.fm</a>.",
"albumImage": "https://lastfm.freetls.fastly.net/i/u/174s/b0c2311a9af7f0edbc8b99450944ca1b.png"
}
My Album.java class so you can see how I write the Album object to Json in case that is the issue.
/**
* Converts the Album object along with its associated Track objects to a JSONObject toString
*
* @return Returns the Album/Track objects as a JSONObject toString
*/
public String toJString() {
String jString = "{}";
try {
jString = this.albumToJObject().toString(0);
} catch (Exception ex) {
System.out.println("Exception in Album toJString: " + ex.getMessage());
}
return jString;
}
/**
* Converts the Track object to a JSONObject.
*
* @return Returns the Track object as a JSONObject.
*/
public JSONObject albumToJObject() {
JSONObject jObject = new JSONObject();
try {
jObject.put("album", albumName);
jObject.put("albumArtist", albumArtist);
jObject.put("albumImage", albumImage);
jObject.put("albumSummary", albumSummary);
jObject.put("albumTracks", (Object)albumTracks);
// System.out.println("Full Album JSONObject: " + jObject.toString());
} catch (Exception ex) {
System.out.println("Exception in Album toJObject: " + ex.getMessage());
}
return jObject;
}
public void writeAlbumToJson() {
try {
Writer output = null;
File file = new File("album.json");
output = new BufferedWriter(new FileWriter(file));
output.write(this.albumToJObject().toString());
output.close();
} catch (Exception ex) {
ex.printStackTrace();
System.out.println("Exception in writeAlbumToJson: " + ex.getMessage());
}
}
Here is the MusicLibrary class declaration and constructor, cleaned up for clarity of what my current code is:
public class MusicLibrary extends Object implements Serializable {
private Map<String, Album> musicLib;
private static final String mFileName = "album.json";
public MusicLibrary() {
this.musicLib = new HashMap<String, Album>();
try {
InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(this.mFileName);
if (inputStream == null) {
inputStream = new FileInputStream(new File(this.mFileName));
}
JSONObject music = new JSONObject(new JSONTokener(inputStream));
Iterator<String> iter = music.keys();
while(iter.hasNext()) {
String key = iter.next();
JSONObject jAlbumObj = music.optJSONObject(key);
if (music.get(key) instanceof JSONObject) {
Album album = new Album(jAlbumObj);
musicLib.put(key, album);
}
}
System.out.println("DEBUG: musicLib HashMap contents: " + musicLib.toString());
} catch (Exception ex) {
ex.printStackTrace();
System.out.println("Exception reading music library " + mFileName + ": " + ex.getMessage());
}
}
