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Building RESTful services using SCA and JAX-RS

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REST is an important aspect of the Web 2.0 world. Building RESTful services can be a challenge as REST is just an architectural style. JAX-RS emerges as the programming model that guides Java …

REST is an important aspect of the Web 2.0 world. Building RESTful services can be a challenge as REST is just an architectural style. JAX-RS emerges as the programming model that guides Java developers to develop services in REST. On the other hand, we often need to assemble services, including RESTful and traditional ones, into an enterprise composite application. SCA gives us the power to define and composite services in a technology neutral fashion. This talk is to share the interesting ideas to combine the power of both SCA and JAX-RS that we explore in Apache Tuscany project with the JAX-RS runtime from Apache Wink project. The Tuscany Java SCA runtime provides the integration with REST services out of the box via several extensions. Tuscany REST binding (binding.rest) leverage JAX-RS annotations to map business operations to HTTP operations such as POST, GET, PUT and DELETE to provide a REST view to SCA services. The REST binding also allows SCA components to invoke existing RESTful services via a JAX-RS annotated interfaces without messing around HTTP clients. JAX-RS applications and resources can be dropped into the SCA assembly as JAX-RS implementation (implementation.jaxrs). Tuscany also enrich the JAX-RS runtime with more databindings to provide support for data representations and transformation without the interventions from application code. This session will teach you how to model, implement, invoke and expose RESTful services using SCA and JAX-RS. We'll walk you through a sample application developed using Apache Tuscany and Wink.


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  • 1. IBM Software Group 1 http://tuscany.apache.org RESTful SCA with Apache Tuscany Luciano Resende lresende@apache.org http://lresende.blogspot.com Jean-Sebastien Delfino jsdelfino@apache.org http://jsdelfino.blogspot.com
  • 2. IBM Software Group 2 http://tuscany.apache.org Agenda •  What is Apache Tuscany •  What is Apache Wink •  RESTFul SCA Overview •  Usage and architecture walk-through -  Including a look at various scenarios •  What’s next •  Getting involved
  • 3. IBM Software Group 3 http://tuscany.apache.org What is Apache Tuscany ?
  • 4. IBM Software Group 4 http://tuscany.apache.org Apache Tuscany •  Apache Tuscany provides a component based programming model which simplifies development, assembly and deployment and management of composite applications. •  Apache Tuscany implements SCA standards defined by OASIS OpenCSA and extensions based on real user feedback. 4
  • 5. IBM Software Group 5 http://tuscany.apache.org Building Applications using SCA •  Business functions are defined as SCA Components –  That expose services -  Using different communication protocols (bindings) –  And have dependencies on other services through References Store Catalog Currency Converter http currencyCode=USD Fruit Catalog ShoppingCart atom jsonrpc Collection Total
  • 6. IBM Software Group 6 http://tuscany.apache.org SCA Overview Composite A Component AService Service Binding Web Service JMS SLSB Rest JSONRPC JCA … Reference Binding Web Service JMS SLSB Rest JSONRPC JCA … Component B Service Interface - Java - WSDL Reference Interface Reference property setting Property promotepromote wire Implementation Java BPEL PHP SCA composite Spring EJB module … - Java - WSDL
  • 7. IBM Software Group 7 http://tuscany.apache.org What is Apache Wink?
  • 8. IBM Software Group 8 http://tuscany.apache.org Apache Wink •  Apache Wink is a simple yet solid open source framework for building RESTful Web services. It is comprised of a Server module and a Client module for developing and consuming RESTful Web services. •  The Wink Server module is a complete implementation of the JAX-RS v1.0 specification. On top of this implementation, the Wink Server module provides a set of additional features that were designed to facilitate the development of RESTful Web services. •  The Wink Client module is a Java based framework that provides functionality for communicating with RESTful Web services. The framework is built on top of the JDK HttpURLConnection and adds essential features that facilitate the development of such client applications.
  • 9. IBM Software Group 9 http://tuscany.apache.org RESTful SCA Overview
  • 10. IBM Software Group 10 http://tuscany.apache.org REST-related user stories •  As a developer, I want to expose new or existing services over HTTP in REST styles with the flexibility to use different wire formats including (but not limited to) JSON, XML. •  As a developer, I want to allow RPC services to be accessed via HTTP GET method in REST styles to take advantage of HTTP caching. •  As a developer, I want to configure a service exposed using REST to use different cache control mechanisms to maximize performance of static resources and or cache dynamic content. •  As a developer, I want to invoke existing RESTful services via a business interface without dealing with the HTTP client APIs. •  As a developer, I want to compose services (both RESTful and non- RESTful) into a solution using SCA. November 4, 2010
  • 11. IBM Software Group 11 http://tuscany.apache.org A win-win situation using SCA and JAX-RS •  SCA gives us the power to declare, configure and compose services in a technology neutral fashion. •  REST is an important aspect of the Web 2.0 world. Building RESTful services can be a challenge as REST is just an architectural style. JAX-RS emerges as the standard REST programming model. •  A balanced middle-ground to leverage the power of declarative services using SCA and annotation based REST/HTTP mapping using JAX-RS (without tying business logic to the technology specifics) (try to avoid JAX-RS APIs directly).
  • 12. IBM Software Group 12 http://tuscany.apache.org Tuscany’s offerings for REST •  The Tuscany Java SCA runtime provides the integration with REST services out of the box via several extensions. -  Tuscany REST binding type (binding.rest) •  Leverage JAX-RS annotations to map business operations to HTTP operations such as POST, GET, PUT and DELETE to provide a REST view to SCA services. •  Support RPC over HTTP GET •  Allow SCA components to invoke existing RESTful services via a JAX-RS annotated interfaces without messing around HTTP clients. -  Tuscany JAX-RS implementation type (implementation.jaxrs) •  JAX-RS applications and resources can be dropped into the SCA assembly as JAX-RS implementation (implementation.jaxrs). -  Tuscany also enrich the JAX-RS runtime with more databindings to provide support for data representations and transformation without the interventions from application code.
  • 13. IBM Software Group 13 http://tuscany.apache.org Runtime overview •  Related Tuscany modules -  interface-java-jaxrs (Introspection of JAX-RS annotated interfaces) -  binding-rest (binding.rest XML/Java model) -  binding-rest-runtime (runtime provider) -  implementation-jaxrs (implementation.jaxrs XML/Java model) -  implementation-jaxrs-runtime (runtime provider) •  Tuscany uses Apache Wink 1.1.1-incubating as the JAX-RS runtime -  Contributions were made to the Wink runtime to facilitate embedding Wink and it’s going to be available in Wink 1.1.2 which should be available in the near future
  • 14. IBM Software Group 14 http://tuscany.apache.org Usage and architecture walk-through
  • 15. IBM Software Group 15 http://tuscany.apache.org Use Case #1: Exposing an SCA service to HTTP using REST •  We have an existing SCA service and want to make it RESTful 1.  Define a Java interface with JAX-RS annotations •  Provide URI •  Map between business operations and HTTP methods •  Map Input/Output (Path segments, query parameters, headers, etc) •  Configure wire formats 2.  Each method should have a compatible operation in the SCA service
  • 16. IBM Software Group 16 http://tuscany.apache.org REST Services •  Supports exposing existing SCA components as RESTFul services •  Exposing a service as RESTful resource •  Consuming REST Services - Multiple JavaScript frameworks such as Dojo (XHR) - Regular Web browsers - Regular utilities such as cUrl, wGet, etc - SCA component <component name=”Catalog"> <implementation.java class="services.FruitsCataloglmpl" /> <service name=”Catalog"> <t:binding.rest uri="http://localhost:8080/Cartalog" > <t:wireFormat.json /> <t:operationSelector.jaxrs /> </t:binding.rest> </service> </component> Fruit Catalog json
  • 17. IBM Software Group 17 http://tuscany.apache.org Mapping business interfaces using JAX-RS @Remotable public interface Catalog{ @GET Item[] getItem(); @GET @Path("{id}") Item getItemById(@PathParam("id") String itemId); @POST void addItem(Item item); @PUT void updateItem(Item item); @DELETE @Path("{id}") void deleteItem(@PathParam("id") String itemId); }
  • 18. IBM Software Group 18 http://tuscany.apache.org REST service binding runtime architecture
  • 19. IBM Software Group 19 http://tuscany.apache.org Use Case #2: Allowing HTTP GET access to an SCA RPC service •  We have an existing RPC SCA service and want to allow remote accesses using HTTP GET -  No standard JAX-RS client is defined by the JAX-RS spec -  We need to figure the URI, parameter passing (positional or name/value pairs, headers, etc)
  • 20. IBM Software Group 20 http://tuscany.apache.org RPC Services over HTTP GET •  The REST binding provides mapping your RPC style calls over HTTP GET •  Exposing a service as RESTful resource •  Client Invocation - http://localhost:8085/EchoService?method=echo&msg=Hello RPC - http://localhost:8085/EchoService? method=echoArrayString&msgArray=Hello RPC1&msgArray=Hello RPC2" <component name=”Catalog"> <implementation.java class="services.FruitsCataloglmpl" /> <service name=”Catalog"> <t:binding.rest uri="http://localhost:8080/Cartalog" /> <t:wireFormat.json /> <t:operationSelector.rpc /> </t:binding.rest> </service> </component> Fruit Catalog json
  • 21. IBM Software Group 21 http://tuscany.apache.org Mapping queryString to RPC method parameters @Remotable public interface Echo { String echo(@QueryParam("msg") String msg); int echoInt(int param); boolean echoBoolean(boolean param); String [] echoArrayString(@QueryParam("msgArray") String[] stringArray); int [] echoArrayInt(int[] intArray); }
  • 22. IBM Software Group 22 http://tuscany.apache.org Design note •  As of today, we have a special path to handle the RPC over HTTP GET in the REST binding runtime (operationSelector.rpc). Potentially, we can unify this approach with the runtime design that implements the logic for Use case #1. -  Imaging that you are writing a JAX-RS resource method that supports the RPC style (GET with a list of query parameters, one of them is the “method”) •  For a service method that is not annotated with JAX-RS http method annotations, we will generate a JAX-RS resource class with a mapping so that: -  @GET -  @Path -  @QueryParam for each of the arguments
  • 23. IBM Software Group 23 http://tuscany.apache.org Use Case #3: Access external RESTful services using SCA •  We want to access external RESTful services from an SCA component using SCA references (w/ dependency injection) instead of calling technology APIs such as HTTP client
  • 24. IBM Software Group 24 http://tuscany.apache.org Tuscany SCA client programming model for JAX-RS •  Model as an SCA reference configured with binding.rest in the client component •  Use a JAX-RS annotated interface to describe the outbound HTTP invocations (please note we use the same way to handle inbound HTTP invocations for RESTful services exposed by SCA) •  A proxy is created by Tuscany to dispatch the outbound invocation per the metadata provided by the JAX-RS annotations (such as Path for URI, @GET for HTTP methods, @QueryParam for parameters, etc). -  If no HTTP method is mapped, we use the RPC over HTTP GET
  • 25. IBM Software Group 25 http://tuscany.apache.org Sample configuration •  To invoke a RESTful resource such as getPhotoById(String id): @GET @Path(“/photos/{id}”) InputStream getPhotoById(@PathParam(“id”) String id); •  SCA Reference <reference name=“photoService”> <interface.java interface=“…”/> <tuscany:binding.rest uri=“http://example.com/”/> </reference>
  • 26. IBM Software Group 26 http://tuscany.apache.org REST reference binding runtime architecture
  • 27. IBM Software Group 27 http://tuscany.apache.org Use case #4: Drop in a JAX-RS application into SCA •  We already have a JAX-RS application that is written following JAX-RS programming model (to take full advantage of JAX-RS for the HTTP protocol beyond just business logic). •  We want to encapsulate it as an SCA component so that it can be used in the SCA composite application. (Potentially be able to use SCA @Reference or @Property to inject service providers or property values).
  • 28. IBM Software Group 28 http://tuscany.apache.org Tuscany implemention.jaxrs •  Tuscany introduced an implementation type (under tuscany namespace) to provide out-of-box support for component using JAX- RS
  • 29. IBM Software Group 29 http://tuscany.apache.org implementation.jaxrs runtime archirecture •  Each root resource is translated into an SCA service with binding.rest
  • 30. IBM Software Group 30 http://tuscany.apache.org Sample configuration for implementation.jaxrs •  Composite <composite xmlns="http://docs.oasis-open.org/ns/opencsa/sca/200912" xmlns:tuscany="http://tuscany.apache.org/xmlns/sca/1.1" targetNamespace="http://sample/jaxrs" name="HelloWorld"> <component name="HelloWorldApp"> <tuscany:implementation.jaxrs application="helloworld.jaxrs.HelloWorldApp"/> </component> </composite> HelloWorldApp
  • 31. IBM Software Group 31 http://tuscany.apache.org Summary
  • 32. IBM Software Group 32 http://tuscany.apache.org Summary •  What do we support today ? -  Expose SCA Services as RESTFul services -  Expose RPC SCA Services via HTTP -  Declaratively configure RESTFul services •  Cache Controls Headers and general HTTP Headers -  Consume RESTFul services as SCA References -  Re-use JAX-RS Resources into your composite applications
  • 33. IBM Software Group 33 http://tuscany.apache.org What’s Next ?
  • 34. IBM Software Group 34 http://tuscany.apache.org What’s next ? •  What’s on my “next” todo list ? -  WADL Support via service endpoint ?wadl -  Support for partial response and partial updates •  What’s on yours ? -  Submit your suggestions to our user / development list
  • 35. IBM Software Group 35 http://tuscany.apache.org Getting Involved
  • 36. IBM Software Group 36 http://tuscany.apache.org Resources  Apache Tuscany   http://tuscany.apache.org  Getting Involved   http://tuscany.apache.org/getting-involved.html  Tuscany SCA Java Releases   http://tuscany.apache.org/sca-java-2x-releases.html  Tuscany SCA Java Documentation   http://tuscany.apache.org/java-sca-documentation-menu.html  Apache Wink   http://incubator.apache.org/wink  Getting Involved   http://incubator.apache.org/wink/community.html  Apache Wink Downloads   http://incubator.apache.org/wink/downloads.html
  • 37. IBM Software Group 37 http://tuscany.apache.org Thank You !!!