Android REST client Sample

Question

Even if this thread has accepted answer  feel free to propose other ideas  you do use or like    I ve met these articles    Restful API service Java REST client API for Android   And that lead me to this Google I O 2010 video about REST client applications   http   www youtube com watch v xHXn3Kg2IQE amp feature player embedded   Since now  I ve been creating REST component as static component in my Application controller class      From now  I think  I should change the pattern  Somebody pointed out that Google IOSched application is great sample of how to write REST clients on Android  Somebody else told that this ways is too overcomplicated     So  can anybody please show us what is the best practice  In short and simple way  The IOSched application is too complex for sample use-case

User · Answer

Never use AsynTask to perform network request or whatever that need to be persisted. Async Task are strongly tied to your activity and if the user change the orientation of the screen since the App is re created the AsyncTask will be stopped.

I suggest you to use Service pattern with Intent Service and ResultReceiver. Take a look to RESTDroid. It's a library that allows you to perform any kind of REST request asynchronously and notify your UI with Request Listeners implementing the Virgil Dobjanschi's service pattern.

User · Answer

EDIT 2  October 2017   It is 2017  Just use Retrofit  There is almost no reason to use anything else  EDIT  The original answer is more than a year and a half old at the time of this edit  Although the concepts presented in original answer still hold  as other answers point out  there are now libraries out there that make this task easier for you  More importantly  some of these libraries handle device configuration changes for you  The original answer is retained below for reference  But please also take the time to examine some of the Rest client libraries for Android to see if they fit your use cases  The following is a list of some of the libraries I ve evaluated  It is by no means intended to be an exhaustive list   Volley  this is from Google  RESTDroid RoboSpice Retrofit   Original Answer  Presenting my approach to having REST clients on Android  I do not claim it is the best though    Also  note that this is what I came up with in response to my requirement  You might need to have more layers add more complexity if your use case demands it  For example  I do not have local storage at all  because my app can tolerate loss of a few REST responses  My approach uses just AsyncTasks under the covers  In my case  I  quot call quot  these Tasks from my Activity instance  but to fully account for cases like screen rotation  you might choose to call them from a Service or such  I consciously chose my REST client itself to be an API  This means  that the app which uses my REST client need not even be aware of the actual REST URL s and the data format used  The client would have 2 layers   Top layer  The purpose of this layer is to provide methods which mirror the functionality of the REST API  For example  you could have one Java method corresponding to every URL in your REST API  or even two - one for GETs and one for POSTs   This is the entry point into the REST client API  This is the layer the app would use normally  It could be a singleton  but not necessarily  The response of the REST call is parsed by this layer into a POJO and returned to the app   This is the lower level AsyncTask layer  which uses HTTP client methods to actually go out and make that REST call    In addition  I chose to use a Callback mechanism to communicate the result of the AsyncTasks back to the app  Enough of text  Let s see some code now  Lets take a hypothetical REST API URL - http   myhypotheticalapi com user profile The top layer might look like this            Entry point into the API      public class HypotheticalApi         public static HypotheticalApi getInstance              Choose an appropriate creation strategy                            Request a User Profile from the REST server          param userName The user name for which the profile is to be requested          param callback Callback to execute when the profile is available              public void getUserProfile String userName  final GetResponseCallback callback           String restUrl   Utils constructRestUrlForProfile userName           new GetTask restUrl  new RestTaskCallback                  Override             public void onTaskComplete String response                   Profile profile   Utils parseResponseAsProfile response                   callback onDataReceived profile                            execute                              Submit a user profile to the server          param profile The profile to submit         param callback The callback to execute when submission status is available              public void postUserProfile Profile profile  final PostCallback callback           String restUrl   Utils constructRestUrlForProfile profile           String requestBody   Utils serializeProfileAsString profile           new PostTask restUrl  requestBody  new RestTaskCallback                public void onTaskComplete String response                   callback onPostSuccess                             execute                     Class definition for a callback to be invoked when the response data for the    GET call is available      public abstract class GetResponseCallback                      Called when the response data for the REST call is ready   lt br  gt         This method is guaranteed to execute on the UI thread                  param profile The   code Profile  that was received from the server              abstract void onDataReceived Profile profile                      Additional methods like onPreGet   or onFailure   can be added with default implementations         This is why this has been made and abstract class rather than Interface                        Class definition for a callback to be invoked when the response for the data     submission is available          public abstract class PostCallback                 Called when a POST success response is received   lt br  gt         This method is guaranteed to execute on the UI thread              public abstract void onPostSuccess        Note that the app doesn t use the JSON or XML  or whatever other format  returned by the REST API directly  Instead  the app only sees the bean Profile  Then  the lower layer  AsyncTask layer  might look like this         An AsyncTask implementation for performing GETs on the Hypothetical REST APIs      public class GetTask extends AsyncTask lt String  String  String gt            private String mRestUrl      private RestTaskCallback mCallback                      Creates a new instance of GetTask with the specified URL and callback                  param restUrl The URL for the REST API          param callback The callback to be invoked when the HTTP request                   completes                      public GetTask String restUrl  RestTaskCallback callback           this mRestUrl   restUrl          this mCallback   callback                  Override     protected String doInBackground String    params            String response   null            Use HTTP Client APIs to make the call            Return the HTTP Response body here          return response                  Override     protected void onPostExecute String result            mCallback onTaskComplete result           super onPostExecute result                           An AsyncTask implementation for performing POSTs on the Hypothetical REST APIs              public class PostTask extends AsyncTask lt String  String  String gt           private String mRestUrl          private RestTaskCallback mCallback          private String mRequestBody                                  Creates a new instance of PostTask with the specified URL  callback  and            request body                          param restUrl The URL for the REST API              param callback The callback to be invoked when the HTTP request                       completes              param requestBody The body of the POST request                                  public PostTask String restUrl  String requestBody  RestTaskCallback callback               this mRestUrl   restUrl              this mRequestBody   requestBody              this mCallback   callback                              Override         protected String doInBackground String    arg0                  Use HTTP client API s to do the POST               Return response                              Override         protected void onPostExecute String result                mCallback onTaskComplete result               super onPostExecute result                                       Class definition for a callback to be invoked when the HTTP request        representing the REST API Call completes              public abstract class RestTaskCallback                         Called when the HTTP request completes                          param result The result of the HTTP request                      public abstract void onTaskComplete String result          Here s how an app might use the API  in an Activity or Service   HypotheticalApi myApi   HypotheticalApi getInstance            myApi getUserProfile  quot techie curious quot   new GetResponseCallback                   Override             void onDataReceived Profile profile                      Use the profile to display it on screen  etc                                                          Profile newProfile   new Profile            myApi postUserProfile newProfile  new PostCallback                               Override             public void onPostSuccess                       Display Success                            I hope the comments are sufficient to explain the design  but I d be glad to provide more info

User · Answer

We have open-sourced our lightweight async REST client library for Android  you might find it useful if you have minimal requirements and don t want to handle the multithreading yourself - it is very OK for basic communications but not a full-blown REST client library   It s called libRESTfulClient and can be found on GitHub

User · Answer

There is plenty of libraries out there and I m using this one  https   github com nerde rest-resource  This was created by me  and  as you can see in the documentation  it s way cleaner and simpler than the other ones  It s not focused on Android  but I m using in it and it s working pretty well   It supports HTTP Basic Auth  It does the dirty job of serializing and deserializing JSON objects  You will like it  specially if your API is Rails like

User · Answer

Disclaimer  I am involved in the rest2mobile open source project  Another alternative as a REST client is to use rest2mobile   The approach is slightly different as it uses concrete rest examples to generate the client code for the REST service  The code replaces the REST URL and JSON payloads with native java methods and POJOs  It also automatically handles server connections  asynchronous invocations and POJO to from JSON conversions    Note that this tool comes in different flavors  cli  plugins  android ios js support  and you can use the android studio plugin to generate the API directly into your app    All the code can be found on github here

User · Answer

Developing Android REST client applications  by Virgil Dobjanschi led to much discussion  since no source code was presented during the session or was provided afterwards   The only reference implementation I know  please comment if you know more  is available at Datadroid  the Google IO session is mentioned under  presentation   It is a library which you can use in your own application   The second link asks for the  best  REST framework  which is discussed heavily on stackoverflow  For me the application size is important  followed by the performance of the implementation    Normally I use the plain org json implemantation  which is part of Android since API level 1 and therefore does not increase application size  For me very interesting was the information found on JSON parsers performance in the comments  as of Android 3 0 Honeycomb  GSON s streaming parser is included as android util JsonReader  Unfortunately  the comments aren t available any more  Spring Android  which I use sometimes  supports Jackson and GSON  The Spring Android RestTemplate Module documentation points to a sample app    Therefore I stick to org json or GSON for complexer scenarios  For the architecture of an org json implementation  I am using a static class which represents the server use cases  e g  findPerson  getPerson   I call this functionality from a service and use utility classes which are doing the mapping  project specific  and the network IO  my own REST template for plain GET or POST   I try to avoid the usage of reflection

User · Answer

There is another library with much cleaner API and type-safe data  https   github com kodart Httpzoid  Here is a simple usage example  Http http   HttpFactory create context   http post  http   example com users        data new User  John         execute      Or more complex with callbacks  Http http   HttpFactory create context   http post  http   example com users        data new User  John         handler new ResponseHandler lt Void gt               Override         public void success Void ignore  HttpResponse response                        Override         public void error String message  HttpResponse response                        Override         public void failure NetworkError error                        Override         public void complete                      execute      It is fresh new  but looks very promising

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