simplest way to read json from a URL in java

Question

This might be a dumb question but what is the simplest way to read and parse JSON from URL in Java?

In Groovy, it's a matter of few lines of code. Java examples that I find are ridiculously long (and have huge exception handling block).

All I want to do is to read the content of this link.

Answer 1

I have done the json parser in simplest way, here it is

package com.inzane.shoapp.activity;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(String url) {

    // Making HTTP request
    try {
        // defaultHttpClient
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
            System.out.println(line);
        }
        is.close();
        json = sb.toString();

    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
        System.out.println("error on parse data in jsonparser.java");
    }

    // return JSON String
    return jObj;

}
}

this class returns the json object from the url

and when you want the json object you just call this class and the method in your Activity class

my code is here

String url = "your url";
JSONParser jsonParser = new JSONParser();
JSONObject object = jsonParser.getJSONFromUrl(url);
String content=object.getString("json key");

here the "json key" is denoted that the key in your json file

this is a simple json file example

{
    "json":"hi"
}

Here "json" is key and "hi" is value

This will get your json value to string content.

Answer 2

Here are couple of alternatives versions with Jackson (since there are more than one ways you might want data as):

  ObjectMapper mapper = new ObjectMapper(); // just need one
  // Got a Java class that data maps to nicely? If so:
  FacebookGraph graph = mapper.readValue(url, FaceBookGraph.class);
  // Or: if no class (and don't need one), just map to Map.class:
  Map<String,Object> map = mapper.readValue(url, Map.class);

And specifically the usual (IMO) case where you want to deal with Java objects, can be made one liner:

FacebookGraph graph = new ObjectMapper().readValue(url, FaceBookGraph.class);

Other libs like Gson also support one-line methods; why many examples show much longer sections is odd. And even worse is that many examples use obsolete org.json library; it may have been the first thing around, but there are half a dozen better alternatives so there is very little reason to use it.