parsing JSON array of objects with gson

Question

I'm trying to use gson to parse a JSON file containing an array of objects. I'm getting a "Exception in thread "main" com.google.gson.JsonSyntaxException: java.io.EOFException: End of input at line 1 column 2" error on this line of code:

  RecipeList[] myRecipe = gson.fromJson(theLine, RecipeList[].class);

I am a bit confused about using gson so I don't think I've set things up properly. The data is in this format:

[  {
"id": 10259,
"cuisine": "greek",
"ingredients": [
  "romaine lettuce",
  "black olives"
]  }, {
"id": 25693,
"cuisine": "southern_us",
"ingredients": [
  "plain flour",
  "ground pepper",
  "salt",
  "tomatoes",
  "ground black pepper",
  "thyme"
]  }]

the code trying to read that is:

inputStream = new FileReader("filepath\\file.json");
BufferedReader myReader = new BufferedReader(inputStream);
theLine = myReader.readLine();

Gson gson = new Gson();
RecipeList[] myRecipe = gson.fromJson(theLine, RecipeList[].class);

my RecipeList class, which was intended to store the array of recipe objects in the json file (but I think this must be wrong)

ArrayList<Recipe> recipeArray;

public RecipeList (Recipe recipObj){
    recipeArray.add(recipObj);
}

And my Recipe class, for the creation of each recipe object in the json array:

String recipeID;
String cuisine;
ArrayList<String> ingredients;


public Recipe (String id, String cuisine, ArrayList<String> ingredients){
    this.recipeID = id;
    this.cuisine = cuisine;
    for (int k = 0; k < ingredients.size(); k++){
        this.ingredients.add(ingredients.get(k));
    }
}

I appreciate any help. I'm a bit confused over the reading of the json text using gson and how to create the individual objects from that array.

thanks Rebecca

Haider Ali · Accepted Answer · 2015-09-17 13:11:40Z

1

theLine = myReader.readLine();

you need to read all lines from file until eof.

ex:

    br = new BufferedReader(new FileReader("C:\\testing.txt"));

String line="";
                while ((line = br.readLine()) != null) {
                    theLine+=line;
                }

edited Sep 17, 2015 at 13:11

answered Sep 17, 2015 at 13:04

Haider Ali

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5 Comments

marsupials Over a year ago

That seems to have helped clear the error message. I don't know if the rest is working as its still reading that file (its quite large). Given that its a large file is there any way to process it without having it become 1 long string? What is the line delimiter in a json file? Is it after each object in the array, or something arbitrary?

Haider Ali Over a year ago

Actually you have to read complete file. Format of file dos not change whether its JSON or other file. You need a complete JSON before you parse it to GSON. I can't find any help in that. But you can use StringBuilder instead of String if you think its occupying java heap a lot.

Haider Ali Over a year ago

I think you can parse GSON from InputStream Instead of using String that also can help. Gson gson = new Gson(); Reader reader = new InputStreamReader(source); SearchResponse response = gson.fromJson(reader,SearchResponse.class); Here source will be your file.

marsupials Over a year ago

Thanks. I did try this using "}," as the delimiter as when I output several lines it seemed that it was on a line of its own: while ((line = myReader.readLine()) != null) { while ((line.compareTo("},") != 0)) { theLine += line; } - But it just concatenated "{" and didn't match anything else

marsupials Over a year ago

Just tried to edit my above comment to say that the compareTo wasn't working as the string contained some extra char, probably whitespace. Matching as a substring worked. I might try that to see if I can extract a JSON object 1 object at a time, then pass that to gson to deserialise

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