How to call a RESTful web service from Android?

Question

I have written a REST web service in Netbean IDE using Jersey Framework and Java.

For every request the user needs to provide a username and a password, I know that this authentication is not a best practice (using a curl command like: curl -u username:password -X PUT http://localhsot:8080/user).

Now I want to call a REST web service from an Android Class.

How should I do it?

I have an Android Class which uses DefaultHttpClient and CredentialUsernameAndPassword, but when I run it in Eclipse, sometimes I get a runtime exception or SDK exception.

Answer 1

This is an sample restclient class

public class RestClient {     public enum RequestMethod     {         GET,         POST     }     public int responseCode=0;     public String message;     public String response;     public void Execute(RequestMethod method,String url,ArrayList<NameValuePair> headers,ArrayList<NameValuePair> params) throws Exception     {         switch (method)         {             case GET:             {                 // add parameters                 String combinedParams = "";                 if (params!=null)                 {                     combinedParams += "?";                     for (NameValuePair p : params)                     {                         String paramString = p.getName() + "=" + URLEncoder.encode(p.getValue(),"UTF-8");                         if (combinedParams.length() > 1)                             combinedParams += "&" + paramString;                         else                             combinedParams += paramString;                     }                 }                 HttpGet request = new HttpGet(url + combinedParams);                 // add headers                 if (headers!=null)                 {                     headers=addCommonHeaderField(headers);                     for (NameValuePair h : headers)                         request.addHeader(h.getName(), h.getValue());                 }                 executeRequest(request, url);                 break;             }             case POST:             {                 HttpPost request = new HttpPost(url);                 // add headers                 if (headers!=null)                 {                     headers=addCommonHeaderField(headers);                     for (NameValuePair h : headers)                         request.addHeader(h.getName(), h.getValue());                 }                 if (params!=null)                     request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));                 executeRequest(request, url);                 break;             }         }     }     private ArrayList<NameValuePair> addCommonHeaderField(ArrayList<NameValuePair> _header)     {         _header.add(new BasicNameValuePair("Content-Type","application/x-www-form-urlencoded"));         return _header;     }     private void executeRequest(HttpUriRequest request, String url)     {         HttpClient client = new DefaultHttpClient();         HttpResponse httpResponse;         try         {             httpResponse = client.execute(request);             responseCode = httpResponse.getStatusLine().getStatusCode();             message = httpResponse.getStatusLine().getReasonPhrase();             HttpEntity entity = httpResponse.getEntity();              if (entity != null)             {                 InputStream instream = entity.getContent();                 response = convertStreamToString(instream);                 instream.close();             }         }         catch (Exception e)         { }     }      private static String convertStreamToString(InputStream is)     {         BufferedReader reader = new BufferedReader(new InputStreamReader(is));         StringBuilder sb = new StringBuilder();         String line = null;         try         {             while ((line = reader.readLine()) != null)             {                 sb.append(line + "\n");             }             is.close();         }         catch (IOException e)         { }         return sb.toString();     } } 

Answer 2

Recently discovered that a third party library - Square Retrofit can do the job very well.

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Defining REST endpoint

public interface GitHubService {    @GET("/users/{user}/repos")    List<Repo> listRepos(@Path("user") String user,Callback<List<User>> cb); } 

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Getting the concrete service

RestAdapter restAdapter = new RestAdapter.Builder()     .setEndpoint("https://api.github.com")     .build(); GitHubService service = restAdapter.create(GitHubService.class); 

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Calling the REST endpoint

List<Repo> repos = service.listRepos("octocat",new Callback<List<User>>() {      @Override     public void failure(final RetrofitError error) {         android.util.Log.i("example", "Error, body: " + error.getBody().toString());     }     @Override     public void success(List<User> users, Response response) {         // Do something with the List of Users object returned         // you may populate your adapter here     } }); 

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The library handles the json serialization and deserailization for you. You may customize the serialization and deserialization too.

Gson gson = new GsonBuilder()     .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)     .registerTypeAdapter(Date.class, new DateTypeAdapter())     .create();  RestAdapter restAdapter = new RestAdapter.Builder()     .setEndpoint("https://api.github.com")     .setConverter(new GsonConverter(gson))     .build();