web-services interview questions
Top web-services frequently asked interview questions
Under what conditions would one favor apps talking via a message queue instead of via web services (I just mean XML or JSON or YAML or whatever over HTTP here, not any particular type)?
I have to talk between two apps on a local network. One will be a web app and have to request commands on another app (running on different hardware). The requests are things like creating users, moving files around, and creating directories. Under what conditions would I prefer XML Web Services (or straight TCP or something) to using a Message queue?
The web app is Ruby on Rails, but I think the question is broader than that.
Source: (StackOverflow)
There are various cloud services available today such as Amazon's EC2 and AWS, Apache Hadoop, Microsoft Azure and many others...
So, to which of the above category do they belong and why?
And which type of service is more popular today and why?
Source: (StackOverflow)
I have read articles about the differences between SOAP and REST as a web service communication protocol, but I think that the biggest advantages for REST over SOAP are:
REST is more dynamic, no need for creating and updating UDDI.
REST is not restricted to XML format. REST web services can send
plain text, JSON, and also XML.
But SOAP is more standardized (Ex; security).
So, am I correct in these points?
Source: (StackOverflow)
What's the maximum length of an HTTP GET request? Is there a response error defined that the server can/should return if it receives a GET request exceeds this length?
update: as indicated in the tags, this is in the context of a web service API, although it's interesting to see the browser limits as well.
Source: (StackOverflow)
I am totally confused between WCF and ASMX web services. I have used a lot of web services in my earlier stage, and now there is this new thing introduced called WCF. I can still create WCF that function as a web service. I think there will be more stuff in WCF.
Can anyone provide me any article or difference between WCF and Web services such as which one to use and when?
Source: (StackOverflow)
Is REST a better approach to doing Web Services or is SOAP? Or are they different tools for different problems? Or is it a nuanced issue - that is, is one slightly better in certain arenas than another, etc?
Bounty-Edit:
Now, almost three years later I would like to ask this question again - offering a bounty to encourage an indepth answer. I would especially appreciate information about those concepts and their relation to the PHP-universe and also modern high-end web-applications.
Source: (StackOverflow)
I am having a lot of trouble finding good information on how to call a standard SOAP/WSDL web service with Android. All I've been able to find are either very convoluted documents and references to "kSoap2" and then some bit about parsing it all manually with SAX. OK, that's fine, but it's 2008, so I figured there should be some good library for calling standard web services.
The web service is just basically one created in NetBeans. I would like to have IDE support for generating the plumbing classes. I just need the easiest/most-elegant way to contact a WSDL based web service from an Android-based phone.
Source: (StackOverflow)
I'm looking for guidance on good practices when it comes to return errors from a REST API. I'm working on a new API so I can take it any direction right now. My content type is XML at the moment, but I plan to support JSON in future.
I am now adding some error cases, like for instance a client attempts to add a new resource but has exceeded his storage quota. I am already handling certain error cases with HTTP status codes (401 for authentication, 403 for authorization and 404 for plain bad request URIs). I looked over the blessed HTTP error codes but none of the 400-417 range seems right to report application specific errors. So at first I was tempted to return my application error with 200 OK and a specific XML payload (ie. Pay us more and you'll get the storage you need!) but I stopped to think about it and it seems to soapy (/shrug in horror). Besides it feels like I'm splitting the error responses into distinct cases, as some are http status code driven and other are content driven.
So what is the SO crowd recommendation? Good practices (please explain why!) and also, from a client pov, what kind of error handling in the REST API makes life easier for the client code?
Source: (StackOverflow)
What is the difference between a webservice and an API? Is the difference more than the protocol used to transfer data?
thanks.
Source: (StackOverflow)
This question already has an answer here:
I had server application in asp.net in windows in that I had a web service for that.
How can I call web service in Linux using shell script by using cURL command?
Source: (StackOverflow)
Let's say my web service is located at http://localhost:8080/foo/mywebservice and my WSDL is at http://localhost:8080/foo/mywebservice?wsdl.
Is http://localhost:8080/foo/mywebservice an endpoint, i.e., is it the same as the URI of my web service or where the SOAP messages received and unmarshalled?
Could you please explain to me what it is and what the purpose of it is?
Source: (StackOverflow)
I'm looking to make a service which I can use to make calls to a web-based REST API.
Basically I want to start a service on app init then I want to be able to ask that service to request a url and return the results. In the meantime I want to be able to display a progress window or something similar.
I've created a service currently which uses IDL, I've read somewhere that you only really need this for cross app communication, so think these needs stripping out but unsure how to do callbacks without it. Also when I hit the post(Config.getURL("login"), values) the app seems to pause for a while (seems weird - thought the idea behind a service was that it runs on a different thread!)
Currently I have a service with post and get http methods inside, a couple of AIDL files (for two way communication), a ServiceManager which deals with starting, stopping, binding etc to the service and I'm dynamically creating a Handler with specific code for the callbacks as needed.
I don't want anyone to give me a complete code base to work on, but some pointers would be greatly appreciated.
Code in (mostly) full:
public class RestfulAPIService extends Service {
final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();
public void onStart(Intent intent, int startId) {
super.onStart(intent, startId);
}
public IBinder onBind(Intent intent) {
return binder;
}
public void onCreate() {
super.onCreate();
}
public void onDestroy() {
super.onDestroy();
mCallbacks.kill();
}
private final IRestfulService.Stub binder = new IRestfulService.Stub() {
public void doLogin(String username, String password) {
Message msg = new Message();
Bundle data = new Bundle();
HashMap<String, String> values = new HashMap<String, String>();
values.put("username", username);
values.put("password", password);
String result = post(Config.getURL("login"), values);
data.putString("response", result);
msg.setData(data);
msg.what = Config.ACTION_LOGIN;
mHandler.sendMessage(msg);
}
public void registerCallback(IRemoteServiceCallback cb) {
if (cb != null)
mCallbacks.register(cb);
}
};
private final Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
// Broadcast to all clients the new value.
final int N = mCallbacks.beginBroadcast();
for (int i = 0; i < N; i++) {
try {
switch (msg.what) {
case Config.ACTION_LOGIN:
mCallbacks.getBroadcastItem(i).userLogIn( msg.getData().getString("response"));
break;
default:
super.handleMessage(msg);
return;
}
} catch (RemoteException e) {
}
}
mCallbacks.finishBroadcast();
}
public String post(String url, HashMap<String, String> namePairs) {...}
public String get(String url) {...}
};
A couple of AIDL files:
package com.something.android
oneway interface IRemoteServiceCallback {
void userLogIn(String result);
}
and
package com.something.android
import com.something.android.IRemoteServiceCallback;
interface IRestfulService {
void doLogin(in String username, in String password);
void registerCallback(IRemoteServiceCallback cb);
}
and the service manager:
public class ServiceManager {
final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();
public IRestfulService restfulService;
private RestfulServiceConnection conn;
private boolean started = false;
private Context context;
public ServiceManager(Context context) {
this.context = context;
}
public void startService() {
if (started) {
Toast.makeText(context, "Service already started", Toast.LENGTH_SHORT).show();
} else {
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.startService(i);
started = true;
}
}
public void stopService() {
if (!started) {
Toast.makeText(context, "Service not yet started", Toast.LENGTH_SHORT).show();
} else {
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.stopService(i);
started = false;
}
}
public void bindService() {
if (conn == null) {
conn = new RestfulServiceConnection();
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.bindService(i, conn, Context.BIND_AUTO_CREATE);
} else {
Toast.makeText(context, "Cannot bind - service already bound", Toast.LENGTH_SHORT).show();
}
}
protected void destroy() {
releaseService();
}
private void releaseService() {
if (conn != null) {
context.unbindService(conn);
conn = null;
Log.d(LOG_TAG, "unbindService()");
} else {
Toast.makeText(context, "Cannot unbind - service not bound", Toast.LENGTH_SHORT).show();
}
}
class RestfulServiceConnection implements ServiceConnection {
public void onServiceConnected(ComponentName className, IBinder boundService) {
restfulService = IRestfulService.Stub.asInterface((IBinder) boundService);
try {
restfulService.registerCallback(mCallback);
} catch (RemoteException e) {}
}
public void onServiceDisconnected(ComponentName className) {
restfulService = null;
}
};
private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {
public void userLogIn(String result) throws RemoteException {
mHandler.sendMessage(mHandler.obtainMessage(Config.ACTION_LOGIN, result));
}
};
private Handler mHandler;
public void setHandler(Handler handler) {
mHandler = handler;
}
}
Service init and bind:
// this I'm calling on app onCreate
servicemanager = new ServiceManager(this);
servicemanager.startService();
servicemanager.bindService();
application = (ApplicationState)this.getApplication();
application.setServiceManager(servicemanager);
service function call:
// this lot i'm calling as required - in this example for login
progressDialog = new ProgressDialog(Login.this);
progressDialog.setMessage("Logging you in...");
progressDialog.show();
application = (ApplicationState) getApplication();
servicemanager = application.getServiceManager();
servicemanager.setHandler(mHandler);
try {
servicemanager.restfulService.doLogin(args[0], args[1]);
} catch (RemoteException e) {
e.printStackTrace();
}
...later in the same file...
Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case Config.ACTION_LOGIN:
if (progressDialog.isShowing()) {
progressDialog.dismiss();
}
try {
...process login results...
}
} catch (JSONException e) {
Log.e("JSON", "There was an error parsing the JSON", e);
}
break;
default:
super.handleMessage(msg);
}
}
};
Source: (StackOverflow)
This is not a question - posting it here for reference:
When consuming a WebService, I got the following error:
Request format is unrecognized for URL unexpectedly ending in /myMethodName
Source: (StackOverflow)
I'm planning to develop an app for the iPhone and that app would have to access a couple of SOAP services. While doing some basic checking in the iPhone SDK I was not able to find any support for accessing SOAP services, a bit of Googling lead to the conclusion that there is no support for SOAP in the iPhone SDK.
So if I do want to build that app I'll need to come up with a approach to access SOAP services from the iPhone. What would be the best approach? Any best practices? Did someone already write a library using the functionality that is present in the iPhone SDK to access SOAP services?
(Since the service I need to access is exposed by another party and they only expose it as SOAP, it's unfortunately not an option to switch to another type of interface (e.g. REST based API).
Gero
Source: (StackOverflow)