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Speaker: Kenneth Kousen The JAX-RS 2.0 specification is part of Java EE 7, but can be used now. It contains the expected annotations for the HTTP verbs (@GET, @POST, and so on) and mechanisms for retrieving variables, but only a few methods for doing hypermedia. This presentation will review those techniques by adding both structural and transitional links to resource representations. Groovy is used to simplify the code and also to implement a MessageBodyWriter for JSON data. In addition to simplifying the implementation classes, Groovy also supplies a RESTful client class from the HttpBuilder project. That will be used, as well as the native client implementation classes in JAX-RS 2.0, to build Spock tests for RESTful services.
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RESTful GroovyImplementing JAX-RS with Groovy
REST
Term from Ph.D. thesis by Roy FieldingCo-founder Apache HTTP Server projectPart of IETF working groups for:
URI, HTTP, HTML
Architectural Styles and the Design ofNetwork-based Software Architectures
REST
Representational State Transfer
- Addressable resources- Uniform interface- Content negotiation- Stateless services
Addressable Resources
Use URLs to access items(no verbs in URLs)
Uniform Interface
HTTP verbsGET
POST
PUT
DELETE
---- HEAD
OPTIONS
PATCH
Safe vs Idempotent
Safe → no server side changesGET
Idempotent
Idempotent requests can be repeatedNo additional effects
GETPUTDELETE
Http Status Codes
200s → good200 OK, 201 created, 204 no content
300s → moved400s → you messed up
404 not found, 409 conflict(see 418, 420 for fun)
500s → we messed up
RESTful service
ImplementationsGET → retrieve dataPOST → insert data
set Location header for new itemPUT → update dataDELETE → remove data
RESTful service
Yes, that’s a URL-driven database
RESTful service
Yes, that’s a URL-driven database
(Hypermedia advocates are squirming,but we’ll get there)
Content Negotiation
Client can request representations
Usually via MIME typein Accept header
Stateless Services
No state maintained in service
All interactions via self-contained requests
HATEOAS
HypermediaAsTheEngineOfApplicationState
An unpronounceable acronymwith the word HATE in it
Hypermedia
Goal is true decouplingClient asks for first URLResponse includes links
Works like the web, but programmatically
The Java Approach
JAX-RS 1.1Implements JSR 311 spec
JAX-RS 2.0Implements JSR 339 spec
JAX-RS
ImplementationsJersey (R.I.)RestEasyRestletsRestfulieApache CXF
JAX-RS
Note: Spring REST annotationsdo NOT implement JAX-RS
POGO
Resources are POGOs
Representations are based onMIME-types
Hypermedia comes from links and annotations
Server Side
JAX-RS
Annotations@GET, @POST, @PUT, @DELETE
@Produces, @Consumes
@Path, @PathParam
@Context
JAX-RS
Classes, interfaces, enumsResponse
Response.ResponseBuilder
UriInfo
UriBuilder
MediaType
Client Side
HttpBuilder projectwraps Apache HTTP Clienthttp://groovy.codehaus.org/modules/http-builder/
Source code:https://github.com/jgritman/httpbuilder
Client Side
JAX-RS 2.0 includes client libraryClientBuilder
WebTarget
Hypermedia
Hypermedia
Trivia
Did you know?
Neither the word “hypermedia” nor HATEOASappear anywhere in the JSR 399 specification
(No, I don’t know why either)
Links
Adding transitional linksResponse.ResponseBuilder
link (several overloads)links
Link class
Links
Adding structural linksUse Link attributes inside POGOAdd JAXB annotations
@XmlJavaTypeAdapter(JaxbAdapter)
Links
Customizing links
Groovy API: JsonBuilder
JsonSlurper
Use a custom JAX-RS provider
Custom Provider
Implement:MessageBodyReader<T>
MessageBodyWriter<T>
Summary
JAX-RS 2.0 specificationJersey reference implementation
Hypermedia done through links
Groovy simplifies codeNo major changes unless custom providerHttpBuilder client
