Think Async Embrace and Get Addicted to the

Think Async Embrace and Get Addicted to the Asynchronicity of Java SE and EE Masoud Kalali, Software Engineer, ORACLE, @Masoud. Kalal Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

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Program Agenda 1 Introduction 2 Why to think Async 3 A simple case of using Async 4 JMS (2. 0) 5 Async Servlet 6 Async JAX-RS 7 Async EJBs Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Speakers Masoud Kalali • Software engineer, author, blogger • Long advocate of Glass. Fish and Java EE • Tweets at @Masoud. Kalali Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Why to think Async? • To better model what we develop for • To further decouple – Ease of administration – Ease of tuning – Ease of maintenance • Improve consumers experience – An API consumer – A direct GUI for human use – etc. Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Java EE And ASynchronicity • Long present JMS – To be used almost everywhere • Servlet 3. 0/ 3. 1 – Asynchronous Servlets – None blocking IO • JAX-RS 2. 0 – Server side – Client side • Asynchronous Session Beans – Server side – Client side Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

A simple asynchronous nourished use case Client 8…. 6…. JMS Queue MDB Cache ID, Async. Context 1 4…. Query Requests in JMS 2 7…. 3 Query Processor JMS Queue 2. 1 Async Servlet 1 Consume result chunks and send it back via Async. Context Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 5…. Chunks of Query results

A simple asynchronous nourished use case More details of the Messaging components • One JMS queue for sending the query requests • One JMS queue which will get chunks of query results • An MDB which will consume the query result messages – Uses the cache and the id in the message to pick up the right Async. Context – As long as the message does not say it is done it will not conclude the response • Complete the response when JMS message implies Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

A simple asynchronous nourished use case More details of the Servlet components • Asynchronous Servlet receiving the requests • Caching the Asyn. Context and a query Id • Sending the Query message to the JMS queue – Including the query Id • Leave it to the MDB to update the response • Have a Async. Listener to send proper response if timeouts Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

A simple asynchronous nourished use case Some basics on the client side • A browser • Can be – A SSE client – A COMET, Long Polling request Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

JMS (2. 0) A brief overview Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

JMS: A brief overview I • Broker • Message • Queue – Producers – Consumers • Topic – Publishers – Subscribers Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

JMS 2. 0: A brief overview: • Multiple Consumers Allowed on the Same Topic Subscription • Delivery Delay • Sending Messages Asynchronously – Send the message and get callback when it is acknowledged by broker • JMSXDelivery. Count message property No longer optional • Standard MDB Configuration Properties as part of @Message. Driven – destination. Type – subscription. Durability – acknowledge. Mode – subscription. Name –. . . Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 0 Asynchronous servlet Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 0 Asynchronicity • Why we want it – More throughput – Better architecture mapping • How it works – @Web. Servlet. async. Supported, async-supported in XML config! – Async. Context – Async. Listener Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 0 Asynchronicity : Async. Context • Adding listeners • Doing request dispatching • Accessing Servlet. Request • Accessing Servlet. Response • Concluding the request/response • Setting, getting timeouts Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 0 Asynchronicity : Async. Listener • Get callback on important events on an async request processing • on. Complete(Async. Event async. Event) • on. Error(Async. Event async. Event) • on. Start. Async(Async. Event async. Event) • on. Timeout(Async. Event async. Event) Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 0 Asynchronicity : A little bit of code @Web. Servlet(async. Supported = true, value = ”/query-servlet") public class Query. Servlet extends Http. Servlet { protected void do. Get(Http. Servlet. Request request, Http. Servlet. Response response) throws Servlet. Exception, IOException { String id=. . . ; cache. put(id, request. start. Async()); send. Query. Message(id, request); } } Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 1 Non-blocking IO Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 1: Non-Blocking IO • Why do we want it? • How does it work? – Read. Listener: To read inbound data when available – Write. Listener: To write data when possible – Changes in Servlet. Output. Stream • is. Ready() • set. Write. Listener(…) – Changes in Servlet. Input. Stream • is. Finished() • is. Ready() • set. Read. Listener(…) Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 1: Non-Blocking IO: Read. Listener • To get callbacks on Servlet. Input. Stream events – on. Data. Available – On. All. Data. Read – on. Error Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Servlet 3. 1: Non-Blocking IO: Write. Listener • To get notified on Servlet. Output. Stream events – on. Error – on. Write. Possible Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0 • Why would we need it? • How does it work? – @Asynchronous – Execution. Context for programmatic decision to do or not to do async – Async. Response – @Suspended – Completion. Callback – Connection. Callbck Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: Server-side I How to mark a resource as Asynchronous • On the serverside: – @Asynchronous: Annotate a sub-resource as Asynchronous – Async. Response: Provides results an actions on the running request • • setting timeout registering callbacks resume, cancel suspended request processing updating the response – @Suspended: To inject a suspended Async. Response into a sub-resource parameter Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: Server-side simple code Server Code: @Path("/api/query") public class My. Resource { @Context private Execution. Context ctx; @GET @Produce(“application/json”) @Asynchronous @Path(“api/matching-query”) public void prep. Matching. Query. Result(@Suspended Async. Response ar, @Query. Param String p 1… ) { executor. submit( new Runnable() { public void run() { Json. Object response = get. Query. Result(p 1…); ctx. resume(response); //container thread picks up and continue } }); ctx. suspend(); // Suspend connection and return }…} Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: client-side simple code Client-Side with future Future<Json. Object> future = client. target(“/api/query/matchingquery”). query. Param(. . . ). request(). async(). get(Json. Object. class); try { Json. Object query. Result = future. get(30, Time. Unit. SECONDS); } catch (Timeout. Exception ex) { // } Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: client-side simple code Client-Side with callback Future<Json. Object> future = client. target(“/api/query/matching-query”). query. Param(. . . ). request(). async(). get(new Invocation. Callback<Json. Object>() { @Override public void completed(Json. Object response) { //Invocation happens and some response is back (404, 200, etc. ) } @Override public void failed(Throwable throwable) { //Invocation fails (client side) } }); Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: Server-side II Completion. Callback • Single method interface • void on. Complete(Throwable t) • signal completion of serving a request Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asyncronicity in JAX-RS 2. 0: Server-side III Connection. Callback • Single method interface • void on. Disconnect(Async. Response disconnected) • signals interruption in client connection before completion Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asynchronous And long running jobs in REST Don’t keep unnecessary resources for where not needed! • Multi-step long running jobs not suitable with JAX-RS Async • Send 202 where response is not ready with Location header – Intelligent enough client can query the resource Location with the given Retry-After header Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

EJB 3. 1 Asynchronicity in Session Beans Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asynchronicity in EJB 3. 1 • Works on session beans – fire and forget – Using Future<V> to decide on completion • Async. Result as container specific vehicle – Passes the result to Future<V> • As simple as using @Asynchronous on method/bean • Method should return Future<V> • Client can poll the future for Completion Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asynchronicity in EJB 3. 1: Simple code sample Server-side code @Stateless public class Query. Processor { @Asynchronous public Future<Query. Result> process. Query(Query. Crit crit){ try{ Query. Result result= prep. Query. Result(crit); return new Async. Result(result); }catch(Exception e){ //handle return new Async. Result(FAILURE_RESULT); } }} Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Asynchronicity in EJB 3. 1: Simple code sample cliet-side code @Inject Query. Processor query. Processor; private Json. Object prepare. Query. Result(String. . . params){ Query. Crit crit = new Query. Crit(params) Future<Query. Result> result=query. Processor. prep. Query. Result(crit); //poll the Future. . There is no callback here. . . } } Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Java EE 7 and SSE Asynchronicity in SSE Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Server-Sent Events § HTML 5 component § Client subscribe to event source § Unidirectional channel between server and client § Events can be streamed from server to client when happens § Connection stays open § event handling on client side § on. Message § on. Error § etc. § Subscription resuming Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Server-Sent Events § Can be developed using a plain Servlet § use the right media type § use the correct message format § Jersey provides support not JAX-RS yet § Server side to turn a JAX-RS endpoint to SSE broadcaster § Client side to subscribe and consume SS events Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Comments, Questions? Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Resources • • RESTful Services Patterns and best practices By Bhakti Mehta Bhakti’s blog: https: //www. java. net/blog/bhaktimehta Book’s sample codes: CCL photos used in slides: • https: //www. flickr. com/photos/treehouse 1977/2892417805/ • https: //www. flickr. com/photos/essjay/165928100/ • https: //www. flickr. com/photos/jforth/4413370462/ • https: //www. flickr. com/photos/sakalak/8737872379/ • https: //www. flickr. com/photos/jbparrott/8980026600 • https: //www. flickr. com/photos/pentadact/36593493/ • https: //www. flickr. com/photos/jasohill/4442279347/ • https: //www. flickr. com/photos/mdsharpe/5075953655 • https: //www. flickr. com/photos/chuqvr/8329512894/ Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |