How can I make a request to get/download http://coolsite.com/coolstuff.json in Java/Android
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2 Answers
Android supports all the standard java.net classes. The simplest way to retrieve content via HTTP is to call openStream() on your URL and read it:
URL url = new URL("http://coolsite.com/coolstuff.js");
InputStream in = url.openStream();
InputStreamReader reader = new InputStreamReader(in);
// read the JSON data
There are libraries for reading JSON in Java (see http://json.org/java), but since the format is really simple, you can parse it easily.
3 Comments
mergesort
do you think you can give me an example? I really don't have too much experience with java, or any language for that matter
mergesort
Here is what I get: 05-09 03:42:14.475: ERROR/AndroidRuntime(21974): Caused by: java.lang.reflect.InvocationTargetException 05-09 03:42:14.475: ERROR/AndroidRuntime(21974): at com.application.class.class.query(ClassName.java:57)
Tony the Pony
@angrymonkey: Do you have the full stacktrace?
From a cached copy of:
How-to: Android as a RESTful Client
This is a how-to focused on creating a RESTful java object at Android. I’ve used HTTPClient, HTTPEntry, HTTPGet, HTTPResponse, JSONArray and JSONObject classes. I think it’ll be useful if we need to use a web-service from client application.
I’ve implemented a simple Java Object called RestClient which connects to a given Rest-JSON service. After connection, this object prints response content. Using this content, a JSONObject created. Then, RestClient prints the JSONObject’s content, parses all values of this object and prints them as well. And as a last job, RestClient pushes a sample value to the JSONObject.
I’ve uploaded RestClient. Hope it’ll be useful.
P.s: To get access to internet at Android, following field must be included to AndroidManifest.xml file of the project.
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
RestClient code:
package praeda.muzikmekan;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.util.Log;
public class RestClient {
private static String convertStreamToString(InputStream is) {
/*
* To convert the InputStream to String we use the BufferedReader.readLine()
* method. We iterate until the BufferedReader return null which means
* there's no more data to read. Each line will appended to a StringBuilder
* and returned as String.
*/
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
/* This is a test function which will connects to a given
* rest service and prints it's response to Android Log with
* labels "Praeda".
*/
public static void connect(String url)
{
HttpClient httpclient = new DefaultHttpClient();
// Prepare a request object
HttpGet httpget = new HttpGet(url);
// Execute the request
HttpResponse response;
try {
response = httpclient.execute(httpget);
// Examine the response status
Log.i("Praeda",response.getStatusLine().toString());
// Get hold of the response entity
HttpEntity entity = response.getEntity();
// If the response does not enclose an entity, there is no need
// to worry about connection release
if (entity != null) {
// A Simple JSON Response Read
InputStream instream = entity.getContent();
String result= convertStreamToString(instream);
Log.i("Praeda",result);
// A Simple JSONObject Creation
JSONObject json=new JSONObject(result);
Log.i("Praeda","<jsonobject>\n"+json.toString()+"\n</jsonobject>");
// A Simple JSONObject Parsing
JSONArray nameArray=json.names();
JSONArray valArray=json.toJSONArray(nameArray);
for(int i=0;i<valArray.length();i++)
{
Log.i("Praeda","<jsonname"+i+">\n"+nameArray.getString(i)+"\n</jsonname"+i+">\n"
+"<jsonvalue"+i+">\n"+valArray.getString(i)+"\n</jsonvalue"+i+">");
}
// A Simple JSONObject Value Pushing
json.put("sample key", "sample value");
Log.i("Praeda","<jsonobject>\n"+json.toString()+"\n</jsonobject>");
// Closing the input stream will trigger connection release
instream.close();
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
