How to iterate through a JSON file with multiple root elements using the Gson library in Java?

Question

I have such a JSON file,

Json file

{
    "reviewerID": "A7S2B0I67WNWB", 
    "asin": "0594481813", 
    "reviewerName": "AllyMG", 
    "helpful": [2, 2], 
    "reviewText": "This item is just as was described in the original description, works without any issues to be seen. Good product", 
    "overall": 4.0, 
    "summary": "As expected", 
    "unixReviewTime": 1397606400, 
    "reviewTime": "04 16, 2014"
}
{
    "reviewerID": "A3HICVLF4PFFMN", 
    "asin": "0594481813", 
    "reviewerName": "Amazon Customer", 
    "helpful": [0, 0], 
    "reviewText": "bought for a spare for my 9" Nook HD and it fit perfectly.  Very satisfied with the price much less than on the BN site", 
    "overall": 5.0, 
    "summary": "great fit", 
    "unixReviewTime": 1399248000, 
    "reviewTime": "05 5, 2014"
}
{
    "reviewerID": "ANSKSPEEAKY7S", 
    "asin": "0594481813", 
    "reviewerName": "Gena", 
    "helpful": [1, 1], 
    "reviewText": "My son crewed my HD charger cord so I needed another one, this is exactly like the one my son destroyed.", 
    "overall": 5.0, 
    "summary": "Works Great", 
    "unixReviewTime": 1372032000, 
    "reviewTime": "06 24, 2013"
}

And I want to print the values reviewTextin all three of them.

I have Java code like this

Java Code:

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.stream.JsonReader;
import java.io.FileNotFoundException;
import java.io.FileReader;

public class ReviewText {

    public static void main(String[] args) throws FileNotFoundException {

        JsonParser parser = new JsonParser();
        JsonReader jsonReader = new JsonReader(new FileReader("sample.json"));

        JsonElement jsonTree = parser.parse(jsonReader);

        JsonObject jsonObject = jsonTree.getAsJsonObject();

        JsonElement f1 = jsonObject.get("reviewText");

        System.out.println(f1);

    }
}

But my code only prints the output for the first element. How to print the value reviewTextfor all three of them?

Is the JSON file in the correct format?

Answer 1

Use JsonStreamParserto process multiple top-level elements in a file.

JsonStreamParser parser = new JsonStreamParser(new FileReader("sample.json"));

while (parser.hasNext()) {
    JsonElement object = parser.next();
    System.out.println(object.getAsJsonObject().get("reviewText"));
}

Answer 2

JSON , [{}, {}, {}, ...], JSON .

[
    {
        "reviewerID": "A7S2B0I67WNWB", 
        "asin": "0594481813", 
        "reviewerName": "AllyMG", 
        "helpful": [2, 2], 
        "reviewText": "This item is just as was described in the original description, works without any issues to be seen. Good product", 
        "overall": 4.0, 
        "summary": "As expected", 
        "unixReviewTime": 1397606400, 
        "reviewTime": "04 16, 2014"
    },
    {
        "reviewerID": "A3HICVLF4PFFMN", 
        "asin": "0594481813", 
        "reviewerName": "Amazon Customer", 
        "helpful": [0, 0], 
        "reviewText": "bought for a spare for my 9" Nook HD and it fit perfectly.  Very satisfied with the price much less than on the BN site", 
        "overall": 5.0, 
        "summary": "great fit", 
        "unixReviewTime": 1399248000, 
        "reviewTime": "05 5, 2014"
    }
]