Primary focus of this presentation is on the hypermedia as the engine of application state (HATEOAS) and how HTTP APIs may benefit from it. Provides sneak peek into HAL media type & gives an overview of hypermedia support in Java tools (JAX-RS / HalBuilder and Spring HATEOAS) along with practical suggestions for server-side design of hypermedia API. Also includes quick overview of Richardson Maturity Model based on a set of examples, current API trends.

1. REST
KEEP
CALM
AND
WALK
CHEERFULLY
WITH
HYPERMEDIA
by Vladimir Tsukur for Java Day Kyiv 2014

2. vladimir tsukur
team lead @
PRINCiPAL
ENGINEER @
partner @
flushdia flushdia vladimirtsukur

3. Hypermedia
REST
3 WEB API

4. Hypermedia
REST
4
Richardson
Maturity
Model

5. Hypermedia
REST
5

6. Hypermedia
REST
6
Level 0 - Make a Booking
POST /bookings
{
«createBooking»: {
«room-id»: «kyiv:cosmopolite:std»,
«data»: {
«check-in»: «2014-11-23»,
«check-out»: «2014-12-01»,
«breakfast»: true
}
}
}
request
200 OK
{
«success»: {
«id»: «123»,
«room-id»: «kyiv:president:std»,
«data»: …
}
}
response

7. Hypermedia
REST
7
Level 0 - Read Booking
POST /bookings
{
«getBooking»: {
«id»: «123»
}
}
request
200 OK
{
«success»: {
«id»: «123»,
«room-id»: «kyiv:president:std»,
«data»: …
}
}
response

8. Hypermedia
REST
8
Level 0 / SOAP-like
1. Single URI endpoint: /bookings
2. Single HTTP method: POST
3. Action in payload
4. «RPC»-like
5. Uses HTTP as transport, not app protocol
6. Does not use mechanics of the Web
Flickr SOAP &
XML-RPC APIs

9. Hypermedia
REST
9
Level 2 - Make a Booking
POST /hotels/cosmopolite/rooms/std/bookings
{
«check-in»: «2014-11-23»,
«check-out»: «2014-12-01»,
«breakfast»: true
}
request
200 OK
{
«id»: «123»,
«room-id»: «kyiv:cosmopolite:std»,
«check-in»: …
}
response

10. Hypermedia
REST
10
Level 2 - Read Booking
GET /bookings/123
request
200 OK
{
«id»: «123»,
«room-id»: «kyiv:cosmopolite:std»,
«check-in»: …
}
response

11. URI Template Contract
Hypermedia
REST
11
URL Methods
/hotels GET = retrieve hotels
/hotels/{id} GET = retrieve hotel
/hotels/{id}/rooms/{roomId}/bookings POST = create booking
/bookings GET = retrieve bookings
/bookings/{id}
GET = retrieve booking!
PATCH = update booking!
PUT = replace booking!
DELETE = update booking
/bookings/{id}/payment POST = pay

12. Level 2 / CRUD-like
1. Many URIs, many verbs
2. Use mechanics of the Web (partially)
3. NO hypermedia
Hypermedia
REST
12
Amazon S3
Twitter API
Google APIs

13. Hypermedia
REST
13
Level 3?

14. Hypermedia
REST
14
Take a REST
https://github.com/flushdia/take-a-REST

15. Hypermedia
REST
15
Resource State
What is stored on the server
(beyond session)

16. Hypermedia
REST
16
Application State
Where you ARE in the
interaction / session
Pending Confirmed
Served
create
update
rejected
cancel Cancelled
"live"
confirmed
Rejected
update
delete

17. Hypermedia
REST
17
H ypertext
A s
T he
E ngine
O f
A pplication
S tate

18. Hypermedia
REST
18
link
{
«take-a-rest:hotel»: {
«href»: «http://localhost:8080/api/hotels/2»
}
}
‣ URI - identifies a resource with which the
consumer can interact to progress the application
protocol
‣ rel - contains semantic markup (=> verb, headers,
structure of the payload)

19. Hypermedia
REST
19
Domain
Application
Protocol

20. Hypermedia
REST
20

21. Hypermedia
REST
21
Booking
payment N/A - to be paid on the spot
N/A

22. Client
Hypermedia
REST
22
if (booking.links.has("payment")) {
// draw payment button / UI
}
Hypermedia client
does NOT break, because it does
NOT expect link to be always
available

23. Hypermedia
REST
23
Booking
service link added - new functionality
N/A

24. Hypermedia
REST
24
Upgraded / new client
MAY leverage new
features when updated.
!
Existing clients stay intact

25. Hypermedia
REST
25
Knowledge of
non-hypermedia client

26. Hypermedia
REST
26
Knowledge of
hypermedia client
• server leads the client
• media type is at the center

27. Hypermedia
REST
27
Client may
know HOW,
but
NOT WHEN

28. Hypermedia
REST
28
profit
• API: explorable & self-documented
• Client:
• No URL construction
• No domain logic replication
• Less coupling
• Server:
• Transparent resource relocation
• Easier versioning & evolvability

29. «REST doesn’t eliminate the need for a
clue. What REST does is concentrate that
need for prior knowledge into readily
standardizable forms. That is the essential
distinction between data-oriented and
Hypermedia
REST
29
control-oriented integration.»
Roy T. Fielding, 2008

30. «... It has value because it is far easier to
standardize representation and relation
types than it is to standardize objects
and object-specific interfaces ...»
Hypermedia
REST
Roy T. Fielding, 2008
30

31. Hypermedia
REST
31
cons
• efficiency
• tooling
• understanding
by developer community

32. Hypermedia
REST
32
Is somebody
doing hypermedia?

33. Hypermedia
REST
33

34. «A REST API should spend almost all of its
descriptive effort in defining the media
type(s) used for representing resources and
driving application state, or in defining
Hypermedia
REST
34
extended relation names and/or
hypertext-enabled mark-up for existing
standard media types.»
Roy T. Fielding, 2008

35. Hypermedia Factors / Control Data Support
Hypermedia
REST
35
IANA Link Relations
Name Description RFC
self Conveys an identifier for the link's context. RFC4287
first An IRI that refers to the furthest preceding resource in a series of
resources. RFC5988
last An IRI that refers to the furthest following resource in a series of
resources. RFC5988
up Refers to a parent document in a hierarchy of documents. RFC5988
item The target IRI points to a resource that is a member of the collection
represented by the context IRI. RFC6573
collection The target IRI points to a resource which represents the collection
resource for the context IRI. RFC6573
edit Refers to a resource that can be used to edit the link's context. RFC5023
prev/previous Indicates that the link's context is a part of a series, and that the previous
in the series is the link target. HTML5
next Indicates that the link's context is a part of a series, and that the next in
the series is the link target. HTML5

36. Hypermedia Factors / Control Data Support
Hypermedia
REST
36
IANA Link Relations
Name Description RFC
create-form The target IRI points to a resource where a submission form can be
obtained. RFC6861
edit-form The target IRI points to a resource where a submission form for editing
associated resource can be obtained. RFC6861
payment Indicates a resource where payment is accepted RFC5988
latest-version Points to a resource containing the latest (e.g., current) version of the
context. RFC5829
profile Identifying that a resource representation conforms to a certain profile,
without affecting the non-profile semantics of the resource
representation.
RFC6906
search Refers to a resource that can be used to search through the link's
context and related resources. OpenSearch
index Refers to an index. HTML4
about Refers to a resource that is the subject of the link's context. RFC6903
help Refers to context-sensitive help. HTML5

37. Hypermedia
REST
37
Hypermedia Factors
What about and ?

38. Hypermedia
REST
JSON JSON-LD json:api HAL Cj Siren Mason Uber
LE ⊗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗
LO ⊗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗
LT ⊗ ⊗ ⩗ ⩗ ⩗ ⊗ ⩗ ⩗
LN ⊗ ⊗ ⊗ ⊗ ⩗ ⩗ ⩗ ⩗
LI ⊗ ⊗ ⊗ ⊗ ⩗ ⩗ ⩗ ⩗
CR ⊗ ⊗ ⊗ ⩗ ⊗ ⩗ ⩗ ⩗
CU ⊗ ⊗ ⊗ ⊗ ⊗ ⩗ ⩗ ⩗
CM ⊗ ⊗ ⊗ ⊗ ⊗ ⩗ ⩗ ⩗
CL ⊗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗ ⩗
38
JSON-based Media Types

39. Hypermedia
REST
39
Java Support
HAL (Hypertext Application Language):! • Spring HATEOAS
• halbuilder
• halarious
• HyperExpress-Hal
• + JavaScript / Scala / PHP / Ruby / C++ …
Siren: Siren4J
JSON Hyper-Schema: JJSchema
JSON-LD: json-ld-java
Collection+JSON: collection-json.java (Scala support)

40. Hypermedia
REST
40
HAL Overview
Hypertext Application Language:
• simple format
• explorable & discoverable APIs
• for JSON:
! application/vnd+json
• for XML:
application/vnd+xml

41. Hypermedia
REST
41
HAL - state

42. Hypermedia
REST
42
HAL - links

43. HAL - embedded resources
Hypermedia
REST
43

44. Hypermedia
REST
44
HAL - CURies
• Resource documentation
• Link name-spacing

45. Hypermedia
REST
45
HAL APIs

46. Hypermedia
REST
46
Core Domain
(internal business logic)
@Getter
@Setter
public class Booking {
!
..private Long id;
..private LocalDate checkIn;
..private LocalDate checkOut;
..private boolean includeBreakfast;
..private BigDecimal price;
..private Hotel hotel;
!
}

47. Hypermedia
REST
47
Integration Domain
(external, REST API)
@Getter
@Setter
public class BookingRepresentation {
!
..private LocalDate checkIn;
..private LocalDate checkOut;
..private boolean includeBreakfast;
..private BigDecimal price;
..private List<Link> links;
!
}
http://localhost:8080/api/bookings/12345

48. id not necessarily exposed in data:
links encode it to preserve lookup strategy
Hypermedia
REST
http://localhost:8080/api/bookings/12345
48
Integration Domain
(external, REST API)
@Getter
@Setter
public class BookingRepresentation {
!
private LocalDate checkIn;
private LocalDate checkOut;
private boolean includeBreakfast;
private BigDecimal price;
..private List<Link> links;
!
}

49. Core Domain ≠
Integration Domain
Hypermedia
REST
49
• Different clients
• Different reasons to change
• Different rate of change
• IMPORTANT!
• Do not bridge Core domain to Integration domain
(exposing it via REST API directly) to avoid coupling
issues!

50. Hypermedia
REST
50
Embedded Resource
{
"_links": {
…
},
"_embedded": {
"take-a-rest:booking": {
"_links": {
"self": {
"href": "http://~/api/bookings/12345"
}
},
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"paid": false,
"price": 4500,
"hotelName": "Cosmopolite Hotel",
"city": "Kyiv"
}
}
}
/api/bookings

51. Hypermedia
REST
51
Full Resource
{
"_links": {
"curies": {
"href": "http://~/doc/{rel}.html",
"name": "take-a-rest",
"templated": true
},
"self": {
"href": "http://~/api/bookings/1"
},
"take-a-rest:booking-cancellation": {
"href": "http://~/api/bookings/1"
},
"take-a-rest:booking-payment": {
"href": "http://~/api/bookings/1/payment"
},
"take-a-rest:booking-update": {
"href": "http://~/api/bookings/1"
},
"take-a-rest:hotel": {
"href": "http://~/api/hotels/1"
}
},
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"paid": false,
"price": 4500,
"includeBreakfast": true,
"roomType": "SINGLE",
"hotelName": "Cosmopolite Hotel",
"city": "Kyiv"
}
/api/bookings/12345

52. Embedded / Full Resource
• Representations usually require different hypertext
(both data and links)
• Provide separate assembler classes for embedded
and full resource representations!
• Allow property expansion for granularity control:
Hypermedia
REST
52
/api/bookings/12345?props=checkIn,checkOut

53. Hypermedia
REST
53
Tooling Support
1. Media Type
• Representation Model
• Assembly
2. Link Construction
3. Documentation

54. Hypermedia
REST
54
HATEOAS

55. @Getter
@Setter
public class BookingRepresentation extends ResourceSupport {
!
..private LocalDate checkIn;
!
..private LocalDate checkOut;
!
..private boolean includeBreakfast;
!
..private BigDecimal price;
!
}
Hypermedia
HATEOAS
REST
55
Representation

56. BookingRepresentation representation = new BookingRepresentation();
representation.setCheckIn(LocalDate.of(2014, 11, 23));
…
String bookingHref = "http://~/api/bookings/" + id;
representation.add(new Link(bookingHref)); // "self" link
representation.add(new Link(bookingHref, "booking-update"));
…
String hotelHref = "http://~/api/hotels/" + hotel.getId();
representation.add(new Link(hotelHref, "hotel"));
Hypermedia
HATEOAS
REST
56
Filling Representation

57. @Controller
@RequestMapping("/bookings")
public class BookingController {
!
..@RequestMapping(value = "/{id}", method = RequestMethod.GET)
..public HttpEntity<BookingRepr> retrieveById(@PathVariable Long id) {
....BookingRepr representation = …;
....return new HttpEntity<BookingRepr>(representation);
..}
!
}
Hypermedia
HATEOAS
REST
57
Controller

58. Hypermedia
HATEOAS
REST
58
Filling Representation
{
"_links": {
"hotel": {
"href": "http://~/api/hotels/12345"
},
"booking-update": {
"href": "http://~/api/hotels/12345"
}
},
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"includeBreakfast": true,
"price": 10000
}

59. Curie Provider
Hypermedia
HATEOAS
REST
59
@Configuration
@EnableWebMvc
@EnableEntityLinks
@EnableHypermediaSupport(type = HypermediaType.HAL)
public class HypermediaConfiguration {
!
..@Bean
..public CurieProvider curieProvider() {
....return new DefaultCurieProvider(
........"take-a-rest",
........new UriTemplate("http://~/api/doc/{rel}"));
..}
!
}

60. Hypermedia
HATEOAS
REST
60
Curie Provider
{
"_links": {
"curies": {
"href": "http://~/api/doc/rels/{rel}",
"name": "take-a-rest",
"templated": true
},
"take-a-rest:hotel": {
"href": "http://~/api/hotels/12345"
},
"take-a-rest:booking-update": {
"href": "http://~/api/hotels/12345"
},
…
},
…
}

61. Resource Assembler
Hypermedia
HATEOAS
REST
61
@Component
public class BookingRepresentationAssembler extends
....ResourceAssemblerSupport<Booking, BookingRepr> {
!
..public BookingRepresentationAssembler() {
....super(BookingController.class, BookingRepr.class);
..}
!
..@Override
..public BookingRepr toResource(Booking booking) {
....BookingRepr representation = instantiateResource(booking);
....…
....return representation;
..}
!
}

62. @Controller
@RequestMapping("/bookings")
public class BookingController {
!
..@Autowired
..private BookingRepresentationAssembler assembler;
!
..@RequestMapping(value = "/{id}", method = RequestMethod.GET)
..public HttpEntity<BookingRepr> retrieveById(@PathVariable Long id) {
....Booking booking = …;
....BookingRepr representation = assembler.toResource(booking);
....return new HttpEntity<BookingRepr>(representation);
..}
!
}
Hypermedia
HATEOAS
REST
62
Controller -> Assembler

63. JAX-RS REST
@Path("/bookings")
public class BookingResource {
!
..@GET
..@Path("/{id}")
..public BookingRepr retrieveById(@PathParam("id") Long id) {
....BookingRepr representation = …;
....return representation;
..}
!
}
Hypermedia
63
Resource

64. RepresentationFactory factory = new StandardRepresentationFactory();
Representation repr = factory.newRepresentation().withBean(sample);
repr.toString(RepresentationFactory.HAL_JSON);
Hypermedia
REST
64
{
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"includeBreakfast": true,
"price": 10000
}

65. Hypermedia
REST
65
factory.newRepresentation().
....withBean(sample).
....withProperty("paid", false);
{
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"includeBreakfast": true,
"price": 10000,
"paid": false
}

66. factory.newRepresentation()…
........withNamespace("take-a-rest", "http://~/api/doc/rels/{rel}").
........withLink("take-a-rest:hotel", "http://~/api/hotels/12345");
Hypermedia
REST
66
{
"_links": {
"curies": {
"href": "http://~/api/doc/rels/{rel}",
"name": "take-a-rest",
"templated": true
},
"take-a-rest:hotel": {
"href": "http://~/api/hotels/12345"
}
},
…
}

67. factory.newRepresentation()…
........withRepresentation("take-a-rest:booking",
................factory.newRepresentation().withBean(sampleBooking));
Hypermedia
REST
67
{
…
"_embedded": {
"take-a-rest:booking": {
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"includeBreakfast": true,
"price": 10000
}
}
}

68. • XML support via halbuilder-xml
• JAX-RS support via halbuilder-jaxrs
• Scala support via halbuilder-scala
• Representation reader API
• Modular
• Open for customization
• Agnostic to web framework (JAX-RS / Spring / etc.)
Hypermedia
REST
68

69. • setting «self» link:
RepresentationFactory.newRepresentation(String/URI)
• field mapping: Representation.withFields
• mapping delegation: Representation.withRepresentable
• serialization options: pretty print, null stripping,
collating links, etc.
• custom Jackson’s ObjectMapper configuration available
via custom RepresentationFactory
• option to serialize directly to java.io.Writer
• link rel validation
Hypermedia
REST
69

70. Hypermedia
REST
70
Link Construction: How?
based on the request:
scheme server port
{
"_links": {
"take-a-rest:booking": {
"href": "http://localhost:8080/api/bookings/12345"
}
},
…
}
root URL rel. resource URL
based on configuration:

71. @Controller
@RequestMapping("/bookings")
public class BookingController {
!
..@RequestMapping(value = "/{id}", method = RequestMethod.GET)
..public HttpEntity<BookingRepr> retrieveById(@PathVariable Long id) {
....BookingRepr representation = …;
....// add links
....return new HttpEntity<BookingRepr>(representation);
..}
!
}
Hypermedia
HATEOAS
REST
71
Controller
/api/bookings
/api/bookings/{id}

72. Not a Go
Hypermedia
HATEOAS
REST
72
representation.add(
....new Link("http://localhost:8080/api/bookings/" + id)
);
- does not respect request protocol, host and port
- may not URL-escape id properly if it is a String
- breaks if root URL changes
- breaks if controller URL mappings change

73. import static org.spring…ControllerLinkBuilder.linkTo;
!
representation.add(
....linkTo(BookingsController.class).slash(id).withSelfRel()
);
http://localhost:8080/api/bookings /12345
Hypermedia
HATEOAS
REST
73
Standard Approach
- breaks if controller URL mappings change

74. import static org.spring…ControllerLinkBuilder.linkTo;
!
try {
..Method method = BookingsResource.class.getMethod("retrieveById", Long.class);
..representation.add(
....linkTo(BookingsResource.class, method, booking.getId()).withSelfRel()
..);
}
catch (NoSuchMethodException e) {
…
}
Hypermedia
HATEOAS
REST
74
Reflective Approach
http://localhost:8080/api/bookings/12345
- breaks if method is renamed or parameters are
changed
- much more boilerplate :(

75. import static org.spring…ControllerLinkBuilder.linkTo;
import static org.spring…ControllerLinkBuilder.methodOn;
!
representation.add(
....linkTo(methodOn(BookingsController.class).retrieveById(id)).withSelfRel()
);
Hypermedia
HATEOAS
REST
75
Type-safe
http://localhost:8080/api/bookings/12345
✓ (probably) most convenient approach
- return type must be proxy-able
- non-@PathVariable parameters are neglected

76. JAX-RS REST
/api/bookings
@Path("/bookings")
public class BookingResource {
!
..@GET
..@Path("/{id}")
..public BookingRepr retrieveById(@PathParam("id") Long id) {
....BookingRepr representation = …
....// add links
....return representation;
..}
!
}
Hypermedia
/api/bookings/{id}
76
Resource

77. JAX-RS REST
Hypermedia
77
UriBuilder #1
@GET
@Path("/{id}")
public BookingRepr retrieveById(…, @Context UriInfo uri) {
…
..representation.withLink(
...."self",
....uri.getBaseUriBuilder().
......path(BookingsResource.class).
......segment(id.toString()).
......build()
..);
…
}
http://localhost:8080/api
/bookings
/12345
- breaks if resource URL mappings change

78. JAX-RS REST
try {
..Method method = BookingsResource.class.getMethod(
...."retrieveById", Long.class, UriInfo.class);
..representation.withLink(
...."self",
....uri.getBaseUriBuilder().
......path(BookingsResource.class).
......path(method).
......build(id.toString())
..);
}
catch (NoSuchMethodException e) {
..…
} - does not make things robust
Hypermedia
78
- cumbersome
UriBuilder #2

79. JAX-RS REST
UriBuilder #3
Hypermedia
79
representation.withLink(
.."self",
..uri.getBaseUriBuilder().
....path(BookingsResource.class).
....path(BookingsResource.class, "retrieveById").
....build(id.toString())
);
- breaks if method is renamed or
path parameters are changed

80. JAX-RS REST
Hypermedia
80
- URI construction could
have been more robust!

81. JAX-RS REST
Hypermedia
81
LinkBuilder
return Response.ok(representation).
....link("http://~/api/hotels/1", "hotel").
....build();
200 OK HTTP/1.1
Content-Type: application/json
Link: <http://~/api/hotels/321>; rel="hotel"
{
"checkIn": [ 2014, 11, 23 ],
"checkOut": [ 2014, 12, 1 ],
"includeBreakfast": true,
"price": 10000,
"paid": false
}

82. Hypermedia
REST
82
CURie Documentation?
Use Markdown!

83. Hypermedia
REST
83
API Survey
Spring 2014
180+ respondents

84. Hypermedia
REST
84
API Survey - Top Priority
Security Usability Can't decide
18 %
38 %
44 %

85. Hypermedia
REST
85
API Survey - Format
JSON XML Other
2 %
48 % 51 %

86. Hypermedia
REST
86
API Survey - Style (Now)
SOAP CRUD Hypermedia
24 %
39 %
38 %

87. Hypermedia
REST
87
API Survey - Plans to add
28 %
21 %
14 %
7 %
0 %
Hypermedia SOAP CRUD

88. REST
88
Thanks!
Questions?

89. References -
Hypermedia & APIs
• https://www.mnot.net/blog/2013/06/23/linking_apis
• http://oredev.org/2010/sessions/hypermedia-apis
• http://vimeo.com/75106815
• https://www.innoq.com/blog/st/2012/06/hypermedia-benefits-for-m2m-communication/
• http://ws-rest.org/2014/sites/default/files/wsrest2014_submission_12.pdf
• http://www.infoq.com/news/2014/03/ca-api-survey
• https://twitter.com/hypermediaapis
• https://www.youtube.com/watch?v=hdSrT4yjS1g
• https://www.youtube.com/watch?v=mZ8_QgJ5mbs
• http://nordsc.com/ext/classification_of_http_based_apis.html
• http://soabits.blogspot.no/2013/12/selling-benefits-of-hypermedia.html
• https://github.com/mamund/Building-Hypermedia-APIs
• http://amundsen.com/hypermedia/hfactor/
• http://tech.blog.box.com/2013/04/get-developer-hugs-with-rich-error-handling-in-your-api/
• http://odino.org/hypermedia-services-beyond-rest-architectures/
Hypermedia
REST
89

90. References - Media Types
• http://stateless.co/hal_specification.html
• https://github.com/kevinswiber/siren
• https://github.com/JornWildt/Mason
• http://json-ld.org/
• http://amundsen.com/media-types/collection/
• http://soabits.blogspot.com/2013/12/media-types-for-apis.html
• http://soabits.blogspot.no/2013/05/the-role-of-media-types-in-restful-web.
Hypermedia
REST
90
html
• http://soabits.blogspot.com/2014/03/modelling-shipment-example-as.
html
• http://soabits.blogspot.com/2014/02/representing-issue-tracker-with-mason.
html
• https://github.com/mamund/media-types/blob/master/uber-hypermedia.
asciidoc

91. References -
Tutorials & Tools
• https://jax-rs-spec.java.net/
• http://www.oracle.com/technetwork/articles/java/jaxrs20-1929352.html
• http://resteasy.jboss.org/
• https://code.google.com/p/siren4j/
• http://gotohal.net/
• https://www.youtube.com/watch?v=1wEp9yHHtwg
• https://www.youtube.com/watch?v=sVvL12BnIyQ
• https://www.youtube.com/watch?v=pCnXy2Hs2Ag
• https://www.youtube.com/watch?v=_0kmqtWYvaY
• http://kingsfleet.blogspot.com/2014/02/transparent-patch-support-in-jax-rs-20.html
• http://spring.io/guides/tutorials/rest/
• https://jaxb.java.net/
• https://github.com/FasterXML/jackson
• http://zeroturnaround.com/rebellabs/beyond-rest-how-to-build-a-hateoas-api-in-java-with-spring-jax-rs-and-vraptor/
Hypermedia
REST
91