JAX RS and CDI bike the reactive bridge

Copyright © 2017, Oracle and/or its affiliates. All rights reserved. |
JAX-RS and CDI Bike the
(Reactive) Bridge
CON2549
David Delabassée (@delabassee) - Oracle
José Paumard (@josepaumard) - Consultant
October, 2017
2

Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | 3
@delabassee

@JosePaumard
@JosePaumard
https://github.com/JosePaumard
https://www.slideshare.net/jpaumard
https://www.youtube.com/user/JPaumard

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information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
6

reactive
adjective | re·ac·tive | rē-ˈak-tiv
1 :of, relating to, or marked by reaction or reactance
2 a :readily responsive to a stimulus
https://www.merriam-webster.com/dictionary/reactive

JAX-RS
8

JAX-RS 2.1
• JSR 370
– Java EE 8
• Async
– New Reactive Client API
– New method for pausing resquest processing, etc.
• Server-Sent Event support
• JSON-P & JSON-B support
• …
Java API for RESTful Web Services
9

// JAX-RS 2.0
Client client = ClientBuilder.newClient();
WebTarget target = client.target("http://weath.er/api")
.queryParam("city", "Paris");
Forecast forecast = target.request()
.get(Forecast.class);
// …
client.close();
JAX-RS Client API
10

JAX-RS Client API
• Fluent API
– Client Builder  Client  Web Target  Request building  Response
javax.ws.rs.client.Client interface
11
List<Forecast> forecast = ClientBuilder.newClient()
.target("http://weath.er/cities")
.request()
.accept("application/json")
.header("Foo","bar")
.get(new GenericType<List<Forecast>>() {});

JAX-RS Client API
• Synchronous invoker
• Asynchronous invoker
JAX-RS 2.0 Invokers
12
String city = client.target("http://locati.on/api")
.queryParam("city", "Paris")
.request()
.get(String.class);
Future<String> fCity = client.target("http://locati.on/api")
.request()
.async()
.get(String.class);

JAX-RS Client API
Asynchronous invocation
13
.request()
.async()
.get(String.class);
String city = fCity.get();

JAX-RS Client API
14
.request()
.async()
.get(String.class);
try {
String city = fCity.get(5, TimeUnit.SECONDS);
} catch(TimeoutException timeout) {
// …
}

JAX-RS Client API
15
// Set ClientProperties.CONNECT_TIMEOUT & READ_TIMEOUT
.request()
.async()
.get(String.class);
while ( !fCity.isDone() ) {
// response hasn't been received yet
}
String city = fCity.get();

JAX-RS Client API
• InvocationCallback Interface
– javax.ws.rs.client.InvocationCallback<RESPONSE>
• Container will receive async processing events from an invocation
– completed(RESPONSE response)
– failed(Throwable throwable)
16

JAX-RS Client API
WebTarget myResource = client.target("http://examp.le/api/read");
Future<Customer> future = myResource.request(MediaType.TEXT_PLAIN)
.async()
.get(new InvocationCallback<Customer>() {
@Override
public void completed (Customer customer) {
// do something with the customer
}
@Override
public void failed (Throwable throwable) {
// Oops!
}
});
…
InvocationCallback
17

The Travel Service
18

The Travel Service
• Customer details: 150 ms
• Recommended destinations: 250 ms
• Price calculation for a customer and destination: 170 ms (each)
• Weather forecast for a destination: 330 ms (each)
Synchronous
19
5 400 ms

The Travel Service
Asynchronous
20
730 ms

The Travel Service
21

The Travel Service
22
destination.path("recommended").request()
.header("Rx-User", "Async")
.async()
.get(new InvocationCallback<List<Destination>>() {
@Override
public void completed(final List<Destination> recommended) {
final CountDownLatch innerLatch = new CountDownLatch(recommended.size());
final Map<String, Forecast> forecasts =
Collections.synchronizedMap(new HashMap<>());
for (final Destination dest : recommended) {
forecast.resolveTemplate("dest", dest.getDestination()).request()
.async()
.get(new InvocationCallback<Forecast>() {
@Override
public void completed(final Forecast forecast) {
forecasts.put(dest.getDestination(), forecast);
innerLatch.countDown();
}

The Travel Service
23
// cont.
@Override
public void failed(final Throwable throwable) {
innerLatch.countDown();
}
});
}
try {
if (!innerLatch.await(10, TimeUnit.SECONDS)) { // timeout }
} catch (final InterruptedException e) { // Ooops, interrupted! }
// Continue with processing…
}
@Override
public void failed(final Throwable throwable) { // Recommendation error }
});
// ...

JAX-RS Client API
New JAX-RS Reactive Invoker
24
// JAX-RS 2.0
Response response = client.target(recommandationService)
.request()
.get();
Future<Response> futureResponse = client.target(recommandationService)
.request()
.async()
.get();
// JAX-RS 2.1
CompletionStage<Response> completionStageResp = client.target(recommandationService)
.request()
.rx()
.get();

CompletionStage API
• A model for a Task
– That performs an action and may return a value
– That can be triggered by another task
– That may trigger another task
– That can be executed in a different thread
• A CompletionStage is an element of an asynchronous chain
25

CompletionStage Pipeline
26
CS1 CS21
CS22
CS31 CS41
CS32

The Travel Service
27
CompletionStage<JsonObject> queryForecastCS = client.target("forecast")
.queryParam("format", "json").request()
.rx()
.get(JsonObject.class);
Function<JsonObject, Forecast> unmarshallForecast =
jsonObject -> JsonBuilder.create().fromJson(jsonObject.toString(), Forecast.class);
Function<Destination, CompletionStage<Void>> populateWithForecast =
destination ->
queryForecastCS.thenApply(unmarshallForecast)
.thenAccept(forecast -> destination.setForecast(forecast));
Function<Destination, CompletionStage<Void>> populateWithQuotation =
destination ->
queryQuotationCS.thenApply(unmarshallQuotation)
.thenAccept(quotation -> destination.setQuotation(quotation));

The Travel Service
28
Function<Destination, CompletableFuture<Void>> populateDestination =
destination ->
CompletableFuture.allOf(
populateWithForecast.apply(destination).toCompletableFuture(),
populateWithQuotation.apply(destination).toCompletableFuture()
)
.toCompletableFuture();

The Travel Service
29
Function<Destination, CompletableFuture<Void>> populateDestination =
destination ->
CompletableFuture.allOf(
populateWithForecast.apply(destination).toCompletableFuture(),
populateWithQuotation.apply(destination).toCompletableFuture()
)
.toCompletableFuture();
Function<List<Destination>, CompletableFuture<?>[]> populateDestinations =
destinations ->
destinations.stream().map(populateDestination)
.toArray(CompletableFuture[]::new);

The Travel Service
30
@GET
public void populateDestination(@Suspended final AsyncResponse asyncResponse) {
CompletionStage<List<Destination>> destinationCS = client.target("destination")
.rx()
.get(/* some JSONB code */);
CompletionStage<List<Destination>> updatedDestinationsCS =
destinationCS.thenCompose(CompletableFuture.allOf(populateDestinations));
asyncResponse.resume(updatedDestinationsCS.toCompletableFuture().get());
}

The Travel Service
31
@GET
public CompletionStage<Destination> populateDestination() {
CompletionStage<List<Destination>> destinationCS = client.target("destination")
.rx()
.get(/* some JSONB code */);
CompletionStage<List<Destination>> updatedDestinationsCS =
destinationCS.thenCompose(CompletableFuture.allOf(populateDestinations));
return updatedDestinationsCS;
}

Exception Handling
32
CS1 CS21
CS22
CS31 CS41
CS32

Exception Handling
Returns a new CompletionStage
• That completes when the CS completes
• Either with the same result (normal completion)
• Or with the transformed exception
33
exceptionaly()
stage.exceptionaly( // Function
exception -> doSomethingNotTooStupidWith(exception));

Exception Handling
• That completes when the CS completes
• Calls the BiFunction with a null as result or exception
34
handle()
stage.handle( // BiFunction
(result, exception) -> doSomethingWith(result, exception));

Exception Handling
• With the same result or exception as this stage
• That executes the given action when this stage completes
35
whenComplete()
stage.whenComplete( // BiConsumer + async version
(result, exception) -> doSomethingWith(result, exception));

Exception Handling
36
CompletionStage<Void> quotation = client.target("quotation")
.request().rx().get(JsonObject.class)
.thenApply(unmarshallQuotation)
.exceptionnaly(throwable -> null)
.thenAccept(destination::setQuotation);

Exception Handling
37
CompletionStage<Void> quotation = client.target("quotation")
.request().rx().get(JsonObject.class)
.thenApply(unmarshallQuotation)
.handle(((quotation, throwable) -> {
if (throwable == null) {
destination.setQuotation(quotation);
} else {
// try to do something smart with the exception
}
}

JAX-RS Reactive Extensions
• Supported on all HTTP Methods of the Client API
– DELETE
– GET
– HEAD
– OPTIONS
– POST
– PUT
– TRACE
38

JAX-RS Reactive Extensions
• Implementations MUST support an invoker for CompletionStage
• Implementations MAY support other reactive APIs
• Jersey
– CompletionStageRxInvoker (Default)
– RxListenableFutureInvoker – Guava
39
https://github.com/jersey/jersey/tree/master/ext/rx
client.register(RxFlowableInvokerProvider.class);
client.target(...)...
.rx(RxFlowableInvoker.class)
.get();
– RxObservableInvoker – RxJava
– RxFlowableInvoker – RxJava2

CDI
40

CDI 2.0
• JSR 365
– Java EE 8
• Java SE focus
– Modular specification
– CDI Container bootstraping
• Observers Ordering
• Asynchronous Events
• …
Context and Dependency Injection
41

Asynchronous Events
42
// Producer
@Inject
Event<Payload> event;
public void aCriticalBusinessMethod() {
CompletionStage<Payload> cs = event.fireAsync(new Payload());
}
// Consumer
public void anOberser(@ObservesAsync Payload event) {
// do something with the payload
}

Asynchronous Events
43
// Producer
@Inject
CompletionStage<Payload> cs =
event.fireAsync(new Payload(), executor);
}

Asynchronous Events
44
// Producer
@Inject
CompletionStage<Payload> cs =
event.fireAsync(new Payload(), SwingUtilities::invokeLater);
}

Wrap-up
45

Java EE 8 – Modernization & Simplification
46
CDI 2.0
JSON-B 1.0 (*)
Security 1.0 (*)
Bean Validation 2.0
JSF 2.3
Servlet 4.0
JSON-P 1.1
JAX-RS 2.1 Reactive Client API, Server-Sent Events, …
HTTP/2, Server Push, …
Java <-> JSON binding
Updates to JSON standards, JSON Collectors, …
Async Event, Observers ordering, SE support, …
Embrace Java SE 8, new constraints, …
Improved CDI, WebSocket, SE 8 integration, …
Portable Identity Store, Authentication & Security Context

JAX RS and CDI bike the reactive bridge

JAX RS and CDI bike the reactive bridge

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