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up vote 0 down vote favorite

I need to take the values from a JSON array and display them. Below is the code I have used.

getresponse class will send a HTTP request to a PHP page and get the relevant JSON array and the public variable res will hold that returned JSON array.

public class JSONConverter {
     public void convert(){
        getresponse gr=new getresponse();
        String json = gr.res;
        Data data = new Gson().fromJson(json, Data.class);
        System.out.println(data);
    }
}

class Data {
    private String city;
    private int reserve_no;

    public String getCity() { return city; }
    public int getReserve_no() { return reserve_no; }

    public void setTitle(String city) { this.city = city; }
    public void setId(int reserve_no) { this.reserve_no = reserve_no; }

    public String toString() {
        return String.format(city);
    } 
}

getrespose class

public class getresponse {
public static String res;
  public void counter() {
 try {
    URL url = new URL("http://taxi.net/fetchLatest.php");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.setRequestProperty("Accept", "application/json");

    if (conn.getResponseCode() != 200) {
        throw new RuntimeException("Failed : HTTP error code : "
                + conn.getResponseCode());
    }

    BufferedReader br = new BufferedReader(new InputStreamReader(
        (conn.getInputStream())));
            String str;
    while ((str =br.readLine()) != null) {                                  
                    res=str;

    }

    conn.disconnect();

Below is an example of JSON array returned.

[{"reserve_no":"20","city":"city2","street":"street1234","discription":"discription123","date":"2012-10-22 04:47:54","customer":"abc"}]

This code doesn't display the city name of the JSON array returned. can someone help me with this by correcting the code or suggest a better or easier method if any? :)

share|improve this question
    
There is absolutely no correlation between your Data class and the returned JSON, so how would GSON know what it should do? You should probably create a more appropriate Data class, with fields matching the names of the fields in the JSON string. –  fvu Oct 22 '12 at 21:29
    
yeah i did those changes! title as city and id as reserve_no but im not still getting the relevent city name from the response –  senrulz Oct 22 '12 at 21:41
    
So you're saying the posted code sample doesn't really have a relation (anymore) with what you're actually running? That makes it a bit difficult for us to spot problems, don't you think so? You should update your code sample in the question in that case. –  fvu Oct 22 '12 at 21:43
    
i have updated it! please check :) –  senrulz Oct 22 '12 at 21:59

2 Answers 2

up vote 2 down vote accepted

Nikita already gave you the correct solution, but here it is, step by step.

I reduced your problem to this minimal test:

import com.google.gson.Gson;

public class TestGSON 
{
    public static void main( String[] args )
    {
        // that's your JSON sample
        String json = "[{\"reserve_no\":\"20\",\"city\":\"city2\",\"street\":\"street1234\",\"discription\":\"discription123\",\"date\":\"2012-10-22 04:47:54\",\"customer\":\"abc\"}]";
        // note: we tell Gson to expect an **array** of Data
        Data data[] = new Gson().fromJson(json, Data[].class);
        System.out.println(data[0]);
    }
}

The problem is that your JSON fragment is actually an array of objects, not just an object (hence the [] around it). So, you need to tell GSon it must expect an array of Data, not just a Data object. By the way, the exception that's thrown when executing your code as-is already told you so:

Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2

unless of course it got swallowed by an empty catch block

With respect to the Data class: think twice before you override the toString method like you did here. I would drop that method and just do

System.out.println( data[0].getCity() );
share|improve this answer
    
thank you for the explanation! and it worked! :) –  senrulz Oct 23 '12 at 4:16
up vote 2 down vote

Gson maps json string to your class basing on your class properties names. So Data class has property title which is supposed to be mapped to city in json array. You need to rename you property to city so Gson can figure out where to put city from json array.
Or you can use annotations to explicitly map city to title. Check this: https://sites.google.com/site/gson/gson-user-guide#TOC-JSON-Field-Naming-Support

share|improve this answer
    
thank you for your quick reply! even after i have changed them im not getting the city name from the response recieved. anything else i should do to the coding? –  senrulz Oct 22 '12 at 21:40
1  
On more problem. You have and ARRAY of json object. And you want to convert it to single object. You can't. Try something like Data[] datas = new Gson().fromJson(json, Data[].class); –  Nikita Beloglazov Oct 22 '12 at 21:49
    
i want to get few specific values only. as in the example response i want to get only the city2 and 20 values. is there anyway i can do it? –  senrulz Oct 22 '12 at 21:53
    
ok now i got it thank you for your help! :) –  senrulz Oct 23 '12 at 4:16

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