Parsing JSON Array using GSON

Question

I have a basic JSON with all data contained in an array. One would think that it would be simple to retreive a value out of the array, but after multiple hours of trying every different method of parsing I could think of I'm completely lost. Any help would be greatly appreciated. Sorry for the horrid wording of this question.

I know I've attempted reading the JSON as an object using JsonReader and then parsing for the ID field. That would be my latest attempt, the code for the other attempts has already been deleted I'm afraid and I can't provide much information on said attempts

JsonReader reader = new JsonReader(new FileReader(Constants.VersJson));
        reader.beginObject();

        while (reader.hasNext()) {

          String name = reader.nextName();

          reader.beginArray();

          if (name.equals("id")) {

            System.out.println(reader.nextString());

Below I'll include a snippet of the JSON Array.

"versions": [
{
  "id": "2.7",
  "time": "2012-10-25T15:00:00+02:00",
  "releaseTime": "2013-10-25T15:00:00+02:00",
  "type": "Release"
},
{
  "id": "2.6.4",
  "time": "2011-12-2T14:01:07+02:00",
  "releaseTime": "2013-12-2T14:01:07+02:00",
  "type": "Develop"
},
{
  "id": "2.5",
  "time": "2010-11-24T21:05:00+02:00",
  "releaseTime": "2013-11-25T01:04:05+02:00",
  "type": "Develop"

What did you try? Why do you think it would work? Why doesn't it? — Sotirios Delimanolis, Nov 18 '13 at 20:56
When I begin the array before checking the name it throws an IllegalStateException with: Expected BEGIN_ARRAY but was NAME at line 2 column 4. — Andrew Davis, Nov 18 '13 at 21:17
If your JSON is like this `{"versions":[{...}]}`, then you have a JSON Object, which contains a JSON Array which contains many JSON objects. — Sotirios Delimanolis, Nov 18 '13 at 21:21
Ok, I see what you're saying now, I don't know why I didn't realize this on my own. Thank you sir. — Andrew Davis, Nov 18 '13 at 21:28
http://stackoverflow.com/a/17650863/1576416 hope this link will help you solve your problem. — Amrut Bidri, Nov 27 '14 at 14:31

score 2 · Accepted Answer · edited Jun 14 '14 at 18:32

Your json format is not correct which you have posted here correct it for example

{ 
   "versions":[
      {
         "id":"2.7",
         "time":"2012-10-25T15:00:00+02:00",
         "releaseTime":"2013-10-25T15:00:00+02:00",
         "type":"Release"
      },
      {
         "id":"2.6.4",
         "time":"2011-12-2T14:01:07+02:00",
         "releaseTime":"2013-12-2T14:01:07+02:00",
         "type":"Develop"
      }
   ]
}

First Define Classes you will get everything

public class Version {

       private List<Versions> versions;

       public List<Versions> getVersions() {
           return versions;
       }

       public void setVersions(List<Versions> versions) {
           this.versions = versions;
       }

       @Override
       public String toString() {
           return "Version [versions=" + versions + "]";
       }
}

public class Versions {

    private String  id;
    private String  time;
    private String  releaseTime;
    private String  type;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getTime() {
        return time;
    }
    public void setTime(String time) {
        this.time = time;
    }
    public String getReleaseTime() {
        return releaseTime;
    }
    public void setReleaseTime(String releaseTime) {
        this.releaseTime = releaseTime;
    }
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    @Override
    public String toString() {
        return "Versions [id=" + id + ", time=" + time + ", releaseTime="
                + releaseTime + ", type=" + type + "]";
    }
}

Finally you can parse the JSON as like here

JsonReader reader = new JsonReader(new FileReader(Constants.VersJson));
Gson gson = new Gson();
Version version = gson.fromJson(reader, Version.class);

Is there a reason for implementing setters and getters for the classes? For the program I am working on I do not see a use for them. Could you explain when they would be needed? — AvP, Apr 05 '15 at 00:58
@AvP Actually gson is field based because it uses the reflection, In this example fields are private can't accessible to outside of class that why getter/setter. if you have public instance property then no need of setter/getter , but its not good to make them public. further see the detail gson doc. https://sites.google.com/site/gson/gson-design-document — Asif Bhutto, Apr 05 '15 at 18:02

score 0 · Answer 2 · answered Nov 28 '14 at 07:18

i have also faced json array parsing using gson here is my code solved it

this is my reader class functions

JsonReader reader = new JsonReader(new InputStreamReader(new FileInputStream(myFile)));
 System.out.println( reader);
   Gson gson = new Gson();
      JsonParser parser = new JsonParser();
      JsonArray jArray = parser.parse(reader).getAsJsonArray();
       ArrayList<JsonOperations> lcs = new ArrayList<JsonOperations>();
 for(JsonElement obj : jArray )
     {
      JsonOperations cse = gson.fromJson( obj , JsonOperations.class);
        
          lcs.add(cse);
   }
     for ( JsonOperations tUser : lcs)
      {
         System.out.println(tUser);
       }

my json operation class is

public class JsonOperations {
 String match_id, pool_name, team1_name, team1_image, team2_name,
   team2_image, match_date, match_country, match_venue, predicted;

 public JsonOperations() {
  
 }

 public JsonOperations(String match_id, String pool_name, String team1_name,
   String team1_image, String team2_name, String team2_image,
   String match_date, String match_country, String match_venue,
   String predicted) {

  this.match_id = match_id;
  this.pool_name = pool_name;
  this.team1_name = team1_name;
  this.team1_image = team1_image;
  this.team2_name = team2_name;
  this.team2_image = team2_image;
  this.match_date = match_date;
  this.match_country = match_country;
  this.match_venue = match_venue;
  this.predicted = predicted;

 }

 public void set_team1(String team1_name) {

  this.team1_name = team1_name;
 }

 public void set_team2(String team2_name) {

  this.team2_name = team2_name;
 }

 public String get_team1() {

  return team1_name;
 }

 public String get_team2() {

  return team2_name;
 }

 @Override
 public String toString() {
  // TODO Auto-generated method stub
  return this.get_team1() + this.get_team2();
 }

}

Parsing JSON Array using GSON

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