Develop Reference

Netty and MongoDB async callback not working together

I have a simple Netty test server that I would like to query a mongo database and return the result. I've setup the simple hello world tutorial from the Netty repository here: https://github.com/netty/netty/tree/4.0/example/src/main/java/io/netty/example/http/helloworld
I've modified the simple tutorial to add an asynchronous MongoDB call, which returns the same "hello world" string as the example, but after my modification the HTTP call never completes.
Original Method:
public void channelRead(ChannelHandlerContext ctx, Object msg) {
if (msg instanceof HttpRequest) {
HttpRequest req = (HttpRequest) msg;
boolean keepAlive = HttpHeaders.isKeepAlive(req);
FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer(CONTENT));
response.headers().set(CONTENT_TYPE, "text/plain");
response.headers().set(CONTENT_LENGTH, response.content().readableBytes());
if (!keepAlive) {
ctx.write(response).addListener(ChannelFutureListener.CLOSE);
} else {
response.headers().set(CONNECTION, Values.KEEP_ALIVE);
ctx.write(response);
}
}
}
After My Change:
private final MongoCollection<Document> collection = ...
public void channelRead(final ChannelHandlerContext ctx, Object msg) {
if (msg instanceof HttpRequest) {
final HttpRequest req = (HttpRequest) msg;
collection.find(Filters.eq("_id", new ObjectId("..."))).first(new SingleResultCallback<Document>() {
public void onResult(Document document, Throwable throwable) {
boolean keepAlive = HttpUtil.isKeepAlive(req);
FullHttpResponse response = ...
(SAME CODE AS ABOVE)
});
}
}
I can see it's hitting my code, but the response never gets sent to the client. How do I make an async call in the ServerHandler method?

You will need to also call flush() or change write(...) to writeAndFlush(...) to ensure the content is really flushed to the socket.

Disconnect Websocket on server side based on a token passed from UI

My aim is to connect browser clients having proper headers with the server. I pass these headers from StompClient.
My UI code in which i passed token in the header is
function connect() {
var socket = new SockJS('/websocket/api/add');
stompClient = Stomp.over(socket);
stompClient.connect({"token" : "12345"}, function(frame) {
setConnected(true);
console.log('Connected: ' + frame);
});
}
In backend i am able to read the headers in the preSend() method of ChannelInterceptorAdapter
#Override
public Message<?> preSend(Message<?> message, MessageChannel channel) {
MessageHeaders headers = message.getHeaders();
System.out.println("preSend : HEADERS : {}" + headers);
return super.preSend(message, channel);
}
But here i am not able to close the wesocket session. How can we do that?
Also i was able to close the websocket session but i couldn't receive the headers in afterConnectionEstablished() method of WebSocketHandlerDecorator
public void configureWebSocketTransport(final WebSocketTransportRegistration registration) {
registration.addDecoratorFactory(new WebSocketHandlerDecoratorFactory() {
#Override
public WebSocketHandler decorate(final WebSocketHandler handler) {
return new WebSocketHandlerDecorator(handler) {
#Override
public void afterConnectionEstablished(final WebSocketSession session) throws Exception {
session.close(CloseStatus.NOT_ACCEPTABLE);
super.afterConnectionEstablished(session);
}
};
}
});
super.configureWebSocketTransport(registration);
}
Can someone guide me how can i close the websocketsession based on the header we pass from UI at server side?

You can try sending the client's token to the server through a message when connection established, then let the server save that session into a map, whose key is the corresponding token.
So when you want to close a session by its token, you can query for the session from that map using the token.
Sample Code:
Save the session with its token:
#Override
public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {
String messageToString = message.getPayload().toString();
if (messageToString.startsWith("token=")) {
tokenToSessionMapping.put(messageToString.substring("token=".length()));
}
// Other handling message code...
}
Close the session by token:
WebSocketSession sessionByToken = tokenToSessionMapping.get(token);
if (sessionByToken != null && sessionByToken.isOpen()) {
sessionByToken.close(CloseStatus.NOT_ACCEPTABLE);
}
And other things to notice:
Since the tokenToSessionMapping is static and is shared among sessions. You should use a thread-safe implementation such as ConcurrentHashMap.
When the session is closed, you'd better remove the corresponding entry from the map tokenToSessionMapping. Otherwise the map size will just keep growing. You can do this by the override method afterConnectionClosed().
#Override
public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
Log.info("Socket session closed: {}", status.toString());
String foundKey = null;
for (Map.Entry<String, String> entry : tokenToSessionMapping.entrySet()) {
if (Objects.equals(entry.getValue(), session)) {
foundKey = entry.getKey();
}
}
if (foundKey != null) {
tokenToSessionMapping.remove(foundKey);
}
}

server availability checker in Android

I am trying to check internet connection of device first, if Internet is available...I need to check server is online or not. I have searched lot of in stackflow for it but there no where latest solution is available like below
1
2
but none of it is working properly as people comments and my trial. I am checking internet status of device with below code
public static boolean isInternetAvailable(Context context) {
ConnectivityManager connectivity = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
boolean isActiveNetworkConnected = false;
if (connectivity != null) {
NetworkInfo info = connectivity.getActiveNetworkInfo();
if (info != null) {
if (info.getState() == NetworkInfo.State.CONNECTED) {
isActiveNetworkConnected = true;
} else {
isActiveNetworkConnected = false;
}
}
} else {
isActiveNetworkConnected = false;
}
return isActiveNetworkConnected;
}
Let me know anyone have proper solution which can check server available or not with this code.

After checking the internet connectivity, you can simply make a test API hit to check server status. Send the request to server if server respond ok, start next work or in-other case handle server not responding message for user.
Here is a sample using okhttp
public boolean isServerUp(){
private final OkHttpClient client = new OkHttpClient();
public void run() throws Exception {
Request request = new Request.Builder()
.url("your server url here")
.build();
client.newCall(request).enqueue(new Callback() {
#Override public void onFailure(Call call, IOException e) {
e.printStackTrace();
return false;
}
#Override public void onResponse(Call call, Response response) throws IOException {
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
return true;
}
});
}
return false;
}

For checking the current status of the server after network checked, need to check if the response is not null

How to avoid waiting on main thread when adding headers to requests using retrofit?

I use this to config my retrofit:
RestAdapter restAdapter = new RestAdapter.Builder()
//add headers to requests
.setRequestInterceptor(getAuthenticatedRequestInterceptor())
.setEndpoint(BASE_URL)
.setConverter(new GsonConverter(getGson()))
.build();
and The getAuthenticatedRequestInterceptor() method adds headers to request:
public AccountRequestInterceptor getAuthenticatedRequestInterceptor() {
AccountRequestInterceptor interceptor = new AccountRequestInterceptor();
Map<String, String> headers = new HashMap<>();
String accessToken = null;
try {
accessToken = TokenProvider.getInstance(mContext).getToken();
} catch (InterruptedException e) {
}
headers.put(HeadersContract.HEADER_AUTHONRIZATION, O_AUTH_AUTHENTICATION + accessToken);
interceptor.setHeader(headers);
return interceptor;
}
getToken() method is:
private synchronized string getToken() throws InterruptedException {
if (!isRefreshing()) {
//This is very important to call notify() on the same object that we call wait();
final TokenProvider myInstance = this;
setRefreshing(true);
MyApplication.getRestClient().getAccountService().getRefreshedToken(mLoginData.getRefreshToken())
.subscribe(new Observer<LoginResponse>() {
#Override
public void onCompleted() {
synchronized (myInstance) {
setRefreshing(false);
myInstance.notifyAll();
}
}
#Override
public void onError(Throwable e) {
synchronized (myInstance) {
setRefreshing(false);
myInstance.notifyAll();
}
}
#Override
public void onNext(LoginResponse loginResponse) {
synchronized (myInstance) {
mLoginData = loginResponse;
mAccountProvider.saveLoginData(loginResponse);
myInstance.notifyAll();
}
}
});
}
this.wait();
return mLoginData.getToken();
}
The TokenProvider.getInstance(mContext).getToken() has a wait() on main thread to get the response from an async method and i know that is a bad thing to do but i need this here to wait for the response to take the token from it and then return the token.how can i do this in a separate thread to avoid waiting on the main thread?
Note:
1 - that this is called before any request with retrofit.
2 - I read this and i know i can refresh token after a fail request, but for business reasons i want to avoid having an invalid token.
3 - I call MyApplication.getRestClient().getAccountService().login(loginRequest,callback...‌​) in my Activity and before adding token everything happened in background thread. so I want to use my token and do not block the main thread.
UPDATE: I added the following Interceptor to my new OkHttp:
public class RequestTokenInterceptor implements Interceptor {
#Override
public Response intercept(Interceptor.Chain chain) throws IOException {
Request request = chain.request();
Request newRequest;
try {
Log.d("addHeader", "Before");
String token = TokenProvider.getInstance(mContext).getToken();
if (token != null) {
newRequest = request.newBuilder()
.addHeader("Bearer", token)
.build();
} else {
// I want to cancel the request or raise an exception to catch it in onError method
// of retrofit callback.
}
} catch (InterruptedException e) {
Log.d("addHeader", "Error");
e.printStackTrace();
return chain.proceed(request);
}
Log.d("addHeader", "after");
return chain.proceed(newRequest);
}
}
Now how can i cancel the request or raise an exception to catch it in onError method of retrofit callback, if token is null?

It's a little bit strange issue but let me try to help you. :)
As you know you can refresh token after a failed request with retrofit using response interceptor.
Let's try to use interceptor before request.
public class RequestTokenInterceptor implements Interceptor {
#Override
public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
// Here where we'll try to refresh token.
// with an retrofit call
// After we succeed we'll proceed our request
Response response = chain.proceed(request);
return response;
}
}
And when you're creating your api create a new HttpClient:
OkHttpClient client = new OkHttpClient();
client.interceptors().add(new RequestTokenInterceptor());
And add your http client to your adapter like below:
.setClient(new OkClient(client))
If this works, before every request you'll try to refresh token first and then will proceed your api request. So in ui there'll be no difference with your normal api calls.
Edit:
I'm editing my answer too. If you want to return an error in else case if token null, in else case you can create your custom response:
private Response(Builder builder) {
this.request = builder.request;
this.protocol = builder.protocol;
this.code = builder.code;
this.message = builder.message;
this.handshake = builder.handshake;
this.headers = builder.headers.build();
this.body = builder.body;
this.networkResponse = builder.networkResponse;
this.cacheResponse = builder.cacheResponse;
this.priorResponse = builder.priorResponse;
}
or simply you can return a null response. if you build your custom response and set your code not to 200 such as 401 or 400+ you'll receive that response in Retrofit's callbacks failure method. Than you can do what ever you want.
If you return null you'll get a RuntimeException i think and still you can catch response in your callback's failure method.
After you create your own response in else you can create your custom callback and catch your null response and transform your custom error how ever you want like below:
public abstract class DefaultRequestCallback<T> implements Callback<T> {
public abstract void failure(YourCustomException ex);
public abstract void success(T responseBean);
#Override
public void success(T baseResponseBean, Response response) {
if (response == null) {
// Here we catch null response and transform it to our custom Exception
failure(new YourCustomException());
}
} else {
success(baseResponseBean);
}
}
#Override
public void failure(RetrofitError error) {
// Here's your failure method.
// Also you can transform default retrofit errors to your customerrors
YourCustomException ex = new YourCustomException();
failure(ex);
}
}
This can help you i think.
Edit 2:
You can build a new Response like below. There's a builder pattern in Retrofit's Response class. You can check it from there.
Response response = new Response.Builder().setCode(401).setMessage("Error Message").build();

You could make all long actions in AsyncTask doInBackground method, while in onPre- and onPostExecute you could show/hide some progress bars when user is waiting

Ok, I think if you are calling your getAuthenticatedRequestInterceptor() on the main thread and which in turns call getInstance(),in which i feel you would be creating an object of Type TokenProvider hence when you create this object in the main thread your object.wait() runs on main thread hence to run this on a background thread probably modify your getAuthenticatedRequestInterceptor() method to execute the following lines in a new thread.
try {
accessToken = TokenProvider.getInstance(mContext).getToken();
} catch (InterruptedException e) {
}
headers.put(HeadersContract.HEADER_AUTHONRIZATION, O_AUTH_AUTHENTICATION + accessToken);
interceptor.setHeader(headers);
return interceptor;
but this will have problems for notifying your RestAdapter as the main thread will proceed executing, hence i would suggest
you call getAuthenticatedRequestInterceptor() method first in a new thread and then notify your main thread to build your RestAdapter.This will free your main thread but with the strategy you are employing you will have to wait until you receive the token to make any calls.

Java web service : User defined meta-data

I have a SOAP web service implementation on Jboss 4.2.3. I want to add a version number check for the service. Whenever a client makes a call, I will pass the client version number. I will write an interceptor at the server that would check the client version number. If it is a client with a different version number, I would not process the request.
What I want to know is if there is a way to pass the version number from the client in some context parameter other than adding it in the web service method signature?
In general, if I want to pass some custom META-DATA from client to server, how do I do it ?

In general, if I want to pass some custom META-DATA from client to
server, how do I do it ?
This can be achieved through SOAP Message Handlers both side (Client and Server ) in Jax-WS .
Client Side:
The custom-meta-data , like version number, UUID , Signature information can be added via SOAP Headers.
1..Write a VersionNumberHandler as shown below.
public class VersionNumberHandler implements SOAPHandler<SOAPMessageContext> {
private static final String LoggerName = "ClientSideLogger";
private Logger logger;
private final boolean log_p = true; // set to false to turn off
public VersionNumberHandler() {
logger = Logger.getLogger(LoggerName);
}
public boolean handleMessage(SOAPMessageContext ctx) {
if (log_p)
logger.info("handleMessage");
// Is this an outbound message, i.e., a request?
Boolean request_p = (Boolean) ctx
.get(MessageContext.MESSAGE_OUTBOUND_PROPERTY);
// Manipulate the SOAP only if it's a request
if (request_p) {
// Get the Version Number from some property file ,
// to place in the message header.
String versionNumber = "v1.0";
try {
SOAPMessage msg = ctx.getMessage();
SOAPEnvelope env = msg.getSOAPPart().getEnvelope();
SOAPHeader hdr = env.getHeader();
// Ensure that the SOAP message has a header.
if (hdr == null)
hdr = env.addHeader();
QName qname = new QName("http://ticket.example.com/",
"versionnumber");
SOAPHeaderElement helem = hdr.addHeaderElement(qname);
// In SOAP 1.2, setting the actor is equivalent to
// setting the role.
helem.setActor(SOAPConstants.URI_SOAP_ACTOR_NEXT);
helem.setMustUnderstand(true);
helem.addTextNode(versionNumber);
msg.saveChanges();
// For tracking, write to standard output.
msg.writeTo(System.out);
} catch (SOAPException e) {
System.err.println(e);
} catch (IOException e) {
System.err.println(e);
}
}
return true; // continue down the chain
}
public boolean handleFault(SOAPMessageContext ctx) {
if (log_p)
logger.info("handleFault");
try {
ctx.getMessage().writeTo(System.out);
} catch (SOAPException e) {
System.err.println(e);
} catch (IOException e) {
System.err.println(e);
}
return true;
}
public Set<QName> getHeaders() {
if (log_p)
logger.info("getHeaders");
return null;
}
public void close(MessageContext messageContext) {
if (log_p)
logger.info("close");
}
2..Mention this class in the Handler-Chain.xml.
<javaee:handler>
<javaee:handler-class>
com.example.client.handler.VersionNumberHandler
</javaee:handler-class>
</javaee:handler>
3..Add the handler-chain in the client (Stub) also.
#WebServiceClient(name = "TicketWSImplService", targetNamespace = "http://ticket.example.com/", wsdlLocation = "http://localhost:8080/ticket?wsdl")
#HandlerChain(file = "handler-chain.xml")
public class TicketWSImplService extends Service {
#WebMethod
public void method(){
}
Here, we are adding a new header element "versionnumber" and mustunderstand=true, which means the server/intermediaries has to process this element, otherwise Jax-WS-Runtime will throw SOAP Fault exception to the client. Now we need to write a Validator(SOAP Handler) at the server side to validate this version number which is being passed by the clients.
Server Side:
1..Write a VersionNumberValidator as shown below.
public class VersionNumberValidator implements SOAPHandler<SOAPMessageContext> {
#SuppressWarnings("unused")
#Override
public boolean handleMessage(SOAPMessageContext ctx) {
// Is this an inbound message, i.e., a request?
Boolean response_p = (Boolean) ctx
.get(MessageContext.MESSAGE_OUTBOUND_PROPERTY);
// Manipulate the SOAP only if it's incoming.
if (!response_p) {
try {
SOAPMessage msg = ctx.getMessage();
SOAPEnvelope env = msg.getSOAPPart().getEnvelope();
SOAPHeader hdr = env.getHeader();
// Ensure that the SOAP message has a header.
if (hdr == null) {
generateSOAPFault(msg, "No message header.");
return true;
}
Iterator mustUnderstandHeaders = msg.getSOAPHeader()
.examineMustUnderstandHeaderElements(
"http://schemas.xmlsoap.org/soap/actor/next");
String value = null;
while (mustUnderstandHeaders.hasNext()) {
Node next = (Node) mustUnderstandHeaders.next();
System.out.println("mustUnderstandHeaders name:"
+ next.getValue());
if (next.getNodeName().equalsIgnoreCase("versionnumber"))
value = next.getValue();
if (value != null && !value.equalsIgnoreCase("v1.0")) {
generateSOAPFault(msg, "Version Number Mismatch");
}
}
// For tracking, write to standard output.
msg.writeTo(System.out);
} catch (SOAPException e) {
System.err.println(e);
} catch (IOException e) {
System.err.println(e);
}
}
return true; // continue down the chain
}
#Override
public boolean handleFault(SOAPMessageContext ctx) {
return true; // do continue down the chain
}
// For now, no-ops.
#Override
public Set<QName> getHeaders() {
Set<QName> headers = new HashSet<QName>();
QName qName = new QName("http://ticket.example.com/", "versionnumber");
headers.add(qName);
return headers;
}
#Override
public void close(MessageContext messageContext) {
}
private void generateSOAPFault(SOAPMessage msg, String reason) {
try {
SOAPBody body = msg.getSOAPBody();
SOAPFault fault = body.addFault();
QName fault_name = new QName(
SOAPConstants.URI_NS_SOAP_1_2_ENVELOPE, "UltimateReceiver");
fault.setFaultCode(fault_name);
fault.setFaultRole("http://ticket.example.com/versionNumber_validator");
fault.addFaultReasonText(reason, Locale.US);
} catch (SOAPException e) {
}
}
2..Mention this class in the Handler-Chain-server.xml.
<javaee:handler>
<javaee:handler-class>
com.example.client.handler.VersionNumberValidator
</javaee:handler-class>
</javaee:handler>
3..Publish the webservices.
Now, the every client request will be having "version number =v1.0", At the server side , you will be validating this value is correct or not. If it is not correct, SOAPFaultException will be thrown.

You could add it to the http-headers but that would mean your client would need to do this which also means they can change it and give you wrong numbers causing issues on the server. It's only as reliable as the messages being sent in.
Either way, this isn't the right way to restrict access to your Web Service, you should use http basic authentication or if it's version differences then you should create multiple version endpoints giving clients access to the versions they need.
Also, JBoss 4.2.3 is so old it might not even work. See [1]
Mus
[1] https://community.jboss.org/message/534711

It's a bad idea to try to add out-of-band metadata to a web service. Just pick a new URL for each version if the data structures are incompatible. If they are compatible, put the version number inside the request.
This way you can still support interoperation with all different libraries and not require your clients to find a new hoop to jump through for each toolkit.