JSON parsing with Gson

This is an example of JSON parsing on Android with Gson. Google Gson is a Java library that can be used to convert Java Objects into their JSON representation.

In order to parse JSON with Gson, follow these steps:

• Create a class that extends Activity (here called JsonParsingActivity)
• Create an instance of the Gson class
• Use the DefaultHttpClient to retrieve the data if this is a web resource
• Create a class that will represent the model of the input (here called SearchResponse)
• Use the fromJson method in order to parse the JSON input and return the model object

These are demonstrated in the code snippet(s) below:

package com.javacodegeeks.android.json;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

import com.google.gson.Gson;
import com.javacodegeeks.android.json.model.Result;
import com.javacodegeeks.android.json.model.SearchResponse;

public class JsonParsingActivity extends Activity {

    String url = "http://search.twitter.com/search.json?q=javacodegeeks";

    @Override
    public void onCreate(Bundle savedInstanceState) {

  super.onCreate(savedInstanceState);

  setContentView(R.layout.main);

  InputStream source = retrieveStream(url);

  Gson gson = new Gson();

  Reader reader = new InputStreamReader(source);

  SearchResponse response = gson.fromJson(reader, SearchResponse.class);

  Toast.makeText(this, response.query, Toast.LENGTH_SHORT).show();

  List<Result> results = response.results;

  for (Result result : results) {

Toast.makeText(this, result.fromUser, Toast.LENGTH_SHORT).show();

  }

    }

    private InputStream retrieveStream(String url) {

  DefaultHttpClient client = new DefaultHttpClient(); 

  HttpGet getRequest = new HttpGet(url);

  try {

     HttpResponse getResponse = client.execute(getRequest);

     final int statusCode = getResponse.getStatusLine().getStatusCode();

     if (statusCode != HttpStatus.SC_OK) { 

  Log.w(getClass().getSimpleName(), 

"Error " + statusCode + " for URL " + url); 

  return null;

     }

     HttpEntity getResponseEntity = getResponse.getEntity();

     return getResponseEntity.getContent();

  } 

  catch (IOException e) {

     getRequest.abort();

     Log.w(getClass().getSimpleName(), "Error for URL " + url, e);

  }

  return null;

     }

}

package com.javacodegeeks.android.json.model;

import java.util.List;

import com.google.gson.annotations.SerializedName;

public class SearchResponse {

    public List results;

    @SerializedName("max_id")
    public long maxId;

    @SerializedName("since_id")
    public int sinceId;

    @SerializedName("refresh_url")
    public String refreshUrl;

    @SerializedName("next_page")
    public String nextPage;

    @SerializedName("results_per_page")
    public int resultsPerPage;

    public int page;

    @SerializedName("completed_in")
    public double completedIn;

    @SerializedName("since_id_str")
    public String sinceIdStr;

    @SerializedName("max_id_str")
    public String maxIdStr;

    public String query;

}

package com.javacodegeeks.android.json.model;

import com.google.gson.annotations.SerializedName;

public class Result {

    @SerializedName("from_user_id_str")
    public String fromUserIdStr;

    @SerializedName("profile_image_url")
    public String profileImageUrl;

    @SerializedName("created_at")
    public String createdAt;

    @SerializedName("from_user")
    public String fromUser;

    @SerializedName("id_str")
    public String idStr;

    public Metadata metadata;

    @SerializedName("to_user_id")
    public String toUserId;

    public String text;

    public long id;

    @SerializedName("from_user_id")
    public String from_user_id;

    @SerializedName("iso_language_code")
    public String isoLanguageCode;

    @SerializedName("to_user_id_str")
    public String toUserIdStr;

    public String source;

}

package com.javacodegeeks.android.json.model;

import com.google.gson.annotations.SerializedName;

public class Metadata {

    @SerializedName("result_type")
    public String resultType;

}

 
This was an example of how to parse JSON with Gson on Android.

Related Article:

• Android JSON Parsing with Gson Tutorial