JAX-RS 2.0: RESTful Web Services

The following is intended to outline our general product direction. It is intended for 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.2 Copyright © 2012, Oracle and/or its affiliates. All rights reserved. 2011,

JAX-RS Origins •  JAX-RS 1.0 is Java API for RESTful WS •  RESTFul Principles: –  Assign everything an ID –  Link things together –  Use common set of methods –  Allow multiple representations –  Stateless communications5 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: JAX-RS API Resources@Path("/atm/{cardId}") URI Parameterpublic class AtmService { Injection @GET @Path("/balance") @Produces("text/plain") public String balance(@PathParam("cardId") String card, @QueryParam("pin") String pin) { return Double.toString(getBalance(card, pin)); } … HTTP Method Built-in Binding Serialization 7 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: JAX-RS API (contd.) … Custom Serialization @POST @Path("/withdrawal") @Consumes("text/plain") @Produces("application/json") public Money withdraw(@PathParam("card") String card, @QueryParam("pin") String pin, String amount){ return getMoney(card, pin, amount); } } 8 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Requested Features •  Client API •  Client-side and Server-side Asynchronous •  Filters and Interceptors •  Improved Connection Negotiation •  Validation •  Hypermedia •  Alignment with JSR 330 •  Model-View-Controller11 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

JSR 339 Expert Group •  EG Formed in March 2011 •  Oracle Leads: Marek Potociar / Santiago Pericas-G. •  Expert Group: –  Jan Algermissen, Florent Benoit, Sergey Beryozkin (Talend), Adam Bien, Bill Burke (RedHat), Clinton Combs, Bill De Hora, Markus Karg, Sastry Malladi (Ebay), Julian Reschke, Guilherme Silveira, Dionysios Synodinos •  Early Draft 3 published on Jun 7, 2012!12 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

In-Scope Features •  Client API •  Filters and Interceptors •  Client-side and Server-side Asynchronous •  Improved Connection Negotiation •  Validation •  Hypermedia •  Alignment with JSR 330 •  Model-View-Controller14 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

New in JAX-RS 2.0 •  Client API •  Filters and Interceptors •  Client-side and Server-side Asynchronous •  Improved Connection Negotiation •  Validation •  Hypermedia •  Alignment with JSR 33015 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Client API - Motivation •  HTTP client libraries too low level •  Sharing features with JAX-RS server API •  E.g., MBRs and MBWs •  Supported by some JAX-RS 1.0 implementations •  Need for a standard16 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Client API – Old and New •  Client-side API URL url = new URL("http://.../atm/balance");  HttpURLConnection conn = (HttpURLConnection) url.openConnection();  Old conn.setRequestMethod("GET");  conn.setDoInput(true);  conn.setDoOutput(false);    BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));  String line;  while ((line = br.readLine()) != null) {  out.println(line);  }# Client client = ClientFactory.newClient();# String balance = client.target("http://.../atm/balance")# .request()# .get(String.class);# New17 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Client API// Get instance of Client Client client = ClientFactory.newClient(); Can also inject @URI for the target ß // Get account balance String bal = client.target("http://.../atm/balance") .pathParam("card", "111122223333") .queryParam("pin", "9876") .request().get(String.class); 18 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Client API (contd.)// Withdraw some money Money mon = client.target("http://.../atm/withdraw") .pathParam("card", "111122223333") .queryParam("pin", "9876") .request("application/json") .post(text("50.0"), Money.class); 19 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Generic Interface (Command pattern, Batch processing)Invocation inv1 = client.target("http://.../atm/balance")… .request().buildGet(); Invocation inv2 = client.target("http://.../atm/withdraw")… .request() .buildPost(text("50.0")); 20 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Generic Interface (contd.) Collection<Invocation> invs = Arrays.asList(inv1, inv2); Collection<Response> ress = Collections.transform(invs, new F<Invocation, Response>() { public Response apply(Invocation inv) { return inv.invoke(); } }); 21 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Filters & Interceptors – Motivation •  Customize JAX-RS implementations via well-defined extension points •  Use Cases: Logging, Compression, Security, Etc. •  Shared by client and server APIs •  Supported by most JAX-RS 1.0 implementations •  All using slightly different types or semantics23 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Filters •  Non-wrapping extension points •  Pre: Interface RequestFilter •  Post: Interface ResponseFilter •  Part of a filter chain •  Do not call the next filter directly •  Each filter decides to proceed or break chain •  By returning FilterAction.NEXT or FilterAction.STOP 24 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Filter Example: LoggingFilter@Provider class LoggingFilter implements RequestFilter, ResponseFilter { @Override public FilterAction preFilter(FilterContext ctx) throws IOException { logRequest(ctx.getRequest()); return FilterAction.NEXT; } … 25 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Filter Example: LoggingFilter (contd.) @Override public FilterAction postFilter(FilterContext ctx) throws IOException { logResponse(ctx.getResponse()); return FilterAction.NEXT; } } 26 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Interceptors •  Wrapping extension points •  ReadFrom: Interface ReaderInterceptor •  WriteTo: Interface WriterInterceptor •  Part of an interceptor chain •  Call the next handler directly •  Each handler decides to proceed or break chain •  By calling ctx.proceed() 27 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Handler Example: GzipInterceptor!@Provider class GzipInterceptor implements ReaderInterceptor,WriterInterceptor { @Override public Object aroundReadFrom(ReadInterceptorContext ctx) throws IOException { if (gzipEncoded(ctx)) { InputStream old = ctx.getInputStream(); ctx.setInputStream(new GZIPInputStream(old)); } return ctx.proceed(); } … } 28 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Order of Execution Request WriteTo Request ReadFrom Filter Handler Filter Handler ReadFrom Response WriteTo Response Handler Filter Handler Filter Client Server29 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Binding Example: LoggingFilter! @NameBinding // or @Qualifier ? @Target({ElementType.TYPE, ElementType.METHOD}) @Retention(value = RetentionPolicy.RUNTIME) public @interface Logged { } @Provider @Logged public class LoggingFilter implements RequestFilter, ResponseFilter { … } 30 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Binding Example: LoggingFilter! @Path("/") public class MyResourceClass { @Logged @GET @Produces("text/plain") @Path("{name}") public String hello(@PathParam("name") String name) { return "Hello " + name; } } 31 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Asynchronous – Motivation •  Let “borrowed” threads run free! •  Container environment •  Suspend and resume connections •  Suspend while waiting for an event •  Resume when event arrives •  Leverage Servlet 3.X async support (if available) •  Client API support •  Future<RESPONSE>, InvocationCallback<RESPONSE>33 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Suspend and Resume @Path("/async/longRunning") public class MyResource { @Context private ExecutionContext ctx; @GET @Produces("text/plain") public void longRunningOp() { Executors.newSingleThreadExecutor().submit( new Runnable() { public void run() { Thread.sleep(10000); // Sleep 10 secs ctx.resume("Hello async world!"); } }); ctx.suspend(); // Suspend connection and return } … } 34 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: @Suspend Annotation @Path("/async/longRunning") public class MyResource { @Context private ExecutionContext ctx; @GET @Produces("text/plain") @Suspend public void longRunning() { Executors.newSingleThreadExecutor().submit( new Runnable() { public void run() { Thread.sleep(10000); // Sleep 10 secs ctx.resume("Hello async world!"); } }); // ctx.suspend(); Suspend connection and return } … } 35 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Client API Async Support // Build target URI Target target = client.target("http://.../atm/balance")… // Start async call and register callback Future<?> handle = target.request().async().get( new InvocationCallback<String>() { public void complete(String balance) { … } public void failed(InvocationException e) { … } }); // After waiting for a while … If (!handle.isDone()) handle.cancel(true); 36 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Improved Connection Negotiation GET http://.../widgets2 Accept: text/*; q=1 … Path("widgets2") public class WidgetsResource2 { @GET @Produces("text/plain", "text/html") public Widgets getWidget() {...} } 38 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Improved Conneg (contd.) GET http://.../widgets2 Accept: text/*; q=1 … Path("widgets2") public class WidgetsResource2 { @GET @Produces("text/plain;qs=0.5", "text/html;qs=0.75") public Widgets getWidget() {...} } 39 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Validation – Motivation •  Services must validate data •  Bean Validation already provides the mechanism •  Integration into JAX-RS •  Support for constraint annotations in: •  Fields and properties •  Parameters (including request entity) •  Methods (response entities) •  Resource classes41 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Constraint Annotations @Path("/") class MyResourceClass { @POST @Consumes(MediaType.APPLICATION_FORM_URLENCODED) Built-in public void registerUser( @NotNull @FormParam("firstName") String fn, Custom @NotNull @FormParam("lastName") String ln, @Email @FormParam("email") String em) { ... } } 42 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: User defined Constraints @Target({ METHOD, FIELD, PARAMETER }) @Retention(RUNTIME) @Constraint(validatedBy = EmailValidator.class) public @interface Email { ... } class EmailValidator implements ConstraintValidator<Email, String> { public void initialize(Email email) { … } public boolean isValid(String value, ConstraintValidatorContext context) { // Check value is e-mail address … } } 43 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Request Entity Validation@CheckUser1 class User { ... } @Path("/") class MyResourceClass { @POST @Consumes("application/xml") public void registerUser1(@Valid User u) { … } @POST @Consumes("application/json") public void registerUser12(@CheckUser2 @Valid User u){ … } } 44 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Motivation •  REST principles •  Identifiers and Links •  HATEOAS (Hypermedia As The Engine Of App State) •  Link types: •  Structural Links •  Transitional Links46 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Structural vs. Transitional Links Link: <http://.../orders/1/ship>; rel=ship, <http://.../orders/1/cancel>; rel=cancel Transitional ... <order id="1"> <customer>http://.../customers/11</customer> <address>http://.../customers/11/address/1</customer> <items> <item> Structural <product>http://.../products/111</products> <quantity>2</quantity> </item> ... </order> 47 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Example: Using Transitional Links// Server API Response res = Response.ok(order) .link("http://.../orders/1/ship", "ship") .build(); // Client API Response order = client.target(…) .request("application/xml").get(); if (order.getLink(“ship”) != null) { Response shippedOrder = client .target(order.getLink("ship")) .request("application/xml").post(null); … } 48 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

More Information •  JSR: http://jcp.org/en/jsr/detail?id=339 •  Java.net: http://jax-rs-spec.java.net •  User Alias: users@jax-rs-spec.java.net •  All EG discussions forwarded to this list50 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

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JAX-RS 2.0: RESTful Web Services

by Arun Gupta on Jul 17, 2012

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