Pfthb

I have a very simple JSON with reviews for products, like:

 "reviewerID": "A2XVJBSRI3SWDI", 
 "asin": "0000031887", 
 "reviewerName": "abigail", 
 "helpful": [0, 0], 
 "unixReviewTime": 1383523200, 
 "reviewText": "Perfect red tutu for the price. ", 
 "overall": 5.0, 
 "reviewTime": "11 4, 2013", "summary": "Nice tutu"

 
 "reviewerID": "A2G0LNLN79Q6HR", 
 "asin": "0000031887", 
 "reviewerName": "aj_18 "Aj_18"", 
 "helpful": [1, 1], 
 "unixReviewTime": 1337990400, 
 "reviewText": "This was a really cute", 
 "overall": 4.0, 
 "reviewTime": "05 26, 2012", 
 "summary": "Really Cute but rather short."

I'd like to read it into my Java app using GSON. I have built a class to hold results for each review:

public class Review {
 private String reviewerID;
 private String asin;
 private String reviewerName;
 private ArrayList<Integer> helpful;
 private String reviewText;
 private Double overall;
 private String summary;
 private Long unixReviewTime;
 private String reviewTime;

 public Review() 
 this.helpful = Lists.newArrayList();
 
 // some getters and setters...

To read the JSON file, my code is:

Gson gson = new Gson();
JsonReader reader = new JsonReader(new FileReader(filename));
Review data = gson.fromJson(reader, Review.class);
data.toScreen(); // prints to screen some values

With this code, I can only retrieve the first review in the JSON, so my question is: how to iterate through all the reader and get the next reviews? I don't need to store the reviews in a List, just need to access the object once. Any help more than welcome.

You have to fetch the whole data in the list and then do the iteration as it is a file and will become inefficient otherwise.

private static final Type REVIEW_TYPE = new TypeToken<List<Review>>() 
.getType();
Gson gson = new Gson();
JsonReader reader = new JsonReader(new FileReader(filename));
List<Review> data = gson.fromJson(reader, REVIEW_TYPE); // contains the whole reviews list
data.toScreen(); // prints to screen some values

just parse as an array:

Review reviews = new Gson().fromJson(jsonString, Review.class);

then if you need you can also create a list in this way:

List<Review> asList = Arrays.asList(reviews);

P.S. your json string should be look like this:

[
 
 "reviewerID": "A2SUAM1J3GNN3B1",
 "asin": "0000013714",
 "reviewerName": "J. McDonald",
 "helpful": [2, 3],
 "reviewText": "I bought this for my husband who plays the piano.",
 "overall": 5.0,
 "summary": "Heavenly Highway Hymns",
 "unixReviewTime": 1252800000,
 "reviewTime": "09 13, 2009"
 ,
 
 "reviewerID": "A2SUAM1J3GNN3B2",
 "asin": "0000013714",
 "reviewerName": "J. McDonald",
 "helpful": [2, 3],
 "reviewText": "I bought this for my husband who plays the piano.",
 "overall": 5.0,
 "summary": "Heavenly Highway Hymns",
 "unixReviewTime": 1252800000,
 "reviewTime": "09 13, 2009"
 ,

 [...]
]

In case you need to parse it from a file, I find the best solution to use a HashMap<String, String> to use it inside your java code for better manipultion.

Try out this code:

public HashMap<String, String> myMethodName() throws FileNotFoundException

 String path = "absolute path to your file";
 BufferedReader bufferedReader = new BufferedReader(new FileReader(path));

 Gson gson = new Gson();
 HashMap<String, String> json = gson.fromJson(bufferedReader, HashMap.class);
 return json;