JAX-RS 2.0: RESTful Web Services

transcript

JAX-RS 2.0: RESTful Java on Steroids Arun Gupta, Java EE & GlassFish Guy http://blogs.oracle.com/arungupta, @arungupta

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.

Part I: How we got here ?

How We Got Here? •  Shortest intro to JAX-RS 1.0 •  Requested features for JAX-RS 2.0 •  JSR 339: JAX-RS 2.0

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 communications

JAX-RS 1.0 Goals

•  POJO-Based API •  HTTP Centric •  Format Independence •  Container Independence •  Inclusion in Java EE

Example: JAX-RS API

@Path("/atm/{cardId}")public class AtmService { @GET @Path("/balance") @Produces("text/plain") public String balance(@PathParam("cardId") String card, @QueryParam("pin") String pin) { return Double.toString(getBalance(card, pin)); } …

Built-in Serialization

Resources

URI Parameter Injection

HTTP Method Binding

Example: JAX-RS API (contd.) … @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); }}

Custom Serialization

Param Binding

Example: JAX-RS API (contd.)

Param Binding

Example: JAX-RS API (contd.)

Param Binding

Requested Features

•  Client API •  Client-side and Server-side Asynchronous •  Filters and Interceptors •  Improved Connection Negotiation •  Validation •  Hypermedia •  Alignment with JSR 330 •  Model-View-Controller

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!

Part II: Where We Are Going

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-Controller

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 330

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 standard

Client API – Old and New

• Client-side API URL url = new URL("http://.../atm/balance"); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 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);#

Example: Client API

// Get instance of ClientClient client = ClientFactory.newClient();Can also inject @URI for the target ß// Get account balanceString bal = client.target("http://.../atm/balance") .pathParam("card", "111122223333") .queryParam("pin", "9876") .request().get(String.class);

Param Binding

Example: Client API (contd.)

// Withdraw some moneyMoney mon = client.target("http://.../atm/withdraw") .pathParam("card", "111122223333") .queryParam("pin", "9876") .request("application/json") .post(text("50.0"), Money.class);

Param Binding

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"));

Param Binding

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(); } });

Param Binding

New in JAX-RS 2.0

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 semantics

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

Filter Example: LoggingFilter @Providerclass LoggingFilter implements RequestFilter, ResponseFilter { @Override public FilterAction preFilter(FilterContext ctx) throws IOException { logRequest(ctx.getRequest()); return FilterAction.NEXT; } …

Param Binding

Filter Example: LoggingFilter (contd.)

@Override public FilterAction postFilter(FilterContext ctx) throws IOException { logResponse(ctx.getResponse()); return FilterAction.NEXT; } }

Param Binding

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()

Handler Example: GzipInterceptor!@Providerclass 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(); } … }

Client

Order of Execution

Request Filter

WriteTo Handler

ReadFrom Handler

Response Filter

Server

Request Filter

ReadFrom Handler

WriteTo Handler

Response Filter

Binding Example: LoggingFilter!@NameBinding // or @Qualifier ?@Target({ElementType.TYPE, ElementType.METHOD})@Retention(value = RetentionPolicy.RUNTIME)public @interface Logged {}@Provider@Loggedpublic class LoggingFilter implements RequestFilter, ResponseFilter { … }

Param Binding

Binding Example: LoggingFilter!

@Path("/")public class MyResourceClass { @Logged @GET @Produces("text/plain") @Path("{name}") public String hello(@PathParam("name") String name) { return "Hello " + name; }}

Param Binding

New in JAX-RS 2.0

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>

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 } … }

Param Binding

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 } … }

Param Binding

Example: Client API Async Support // Build target URITarget target = client.target("http://.../atm/balance")… // Start async call and register callbackFuture<?> 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);

Param Binding

New in JAX-RS 2.0

Improved Connection Negotiation

GET http://.../widgets2Accept: text/*; q=1…Path("widgets2")public class WidgetsResource2 { @GET @Produces("text/plain", "text/html") public Widgets getWidget() {...}}

Param Binding

Improved Conneg (contd.)

GET http://.../widgets2Accept: text/*; q=1…Path("widgets2")public class WidgetsResource2 { @GET @Produces("text/plain;qs=0.5", "text/html;qs=0.75") public Widgets getWidget() {...}}

Param Binding

New in JAX-RS 2.0

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 classes

Example: Constraint Annotations

@Path("/")class MyResourceClass { @POST @Consumes(MediaType.APPLICATION_FORM_URLENCODED) public void registerUser( @NotNull @FormParam("firstName") String fn, @NotNull @FormParam("lastName") String ln, @Email @FormParam("email") String em) { ... } }

Param Binding

Custom

Built-in

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 … } }

Param Binding

Example: Request Entity Validation @CheckUser1class 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) { … } }

Param Binding

New in JAX-RS 2.0

Motivation

•  REST principles •  Identifiers and Links •  HATEOAS (Hypermedia As The Engine Of App State)

•  Link types: •  Structural Links •  Transitional Links

Example: Structural vs. Transitional Links

Link: <http://.../orders/1/ship>; rel=ship, <http://.../orders/1/cancel>; rel=cancel...<order id="1"> <customer>http://.../customers/11</customer> <address>http://.../customers/11/address/1</customer> <items> <item> <product>http://.../products/111</products> <quantity>2</quantity> </item> ... </order>

Param Binding

Transitional

Structural

Example: Using Transitional Links // Server APIResponse res = Response.ok(order) .link("http://.../orders/1/ship", "ship") .build(); // Client APIResponse order = client.target(…) .request("application/xml").get();if (order.getLink(“ship”) != null) { Response shippedOrder = client .target(order.getLink("ship")) .request("application/xml").post(null); … }

Other Topics Under Consideration •  Better integration with JSR 330 •  Support @Inject and qualifiers

•  High-level client API?

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 list

JAX-RS 2.0: RESTful Web Services

Technology