Kemat Rochi Kemat Rochi - 1 month ago 11
Java Question

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

I have a JSON file like this,

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 of
reviewText
in all three of them.

I have a 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 prints the output only for the first item. How do I print the value of
reviewText
for all three of them?

Is my JSON file in the correct format?

Answer

Use a JsonStreamParser to handle multiple top-level elements in the file.

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

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