Introduction to JAX-RS @ SIlicon Valley Code Camp 2010

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Introduction to JAX-RS
Jitendra Kotamraju

Oct 2010

What this presentation is about ?

• Not the REST style per se
– But, briefly ...
• The basics of JAX-RS

2

Agenda

• What is JAX-RS ?
• JAX-RS Resources
• Standard Methods (uniform interface)
• JAX-RS Representations
• Lots of demos using JAX-RS API
– @Path, HTTP methods, @Produces/@Consumes
– XML, JSON, @xxParam, Response, Application,
– Sub-resource locators, Injection etc

3
©2010 Oracle Corporation

Very Short REST Primer:
Buy This Book

4

REST is an Architectural Style

Set of constraints you apply to the
architecture of a distributed system
to induce desirable properties

5

RESTful Web Services

Application of REST architectural
style to services that utilize Web
standards (URIs, HTTP, HTML,
XML, Atom, RDF etc.)

6

Java API for RESTful Web Services
(JAX-RS)

Standard annotation-driven API that
aims to help developers build
RESTful Web services in Java

7

Status of JAX-RS

• JSR 311: JAX-RS 1.1 released Nov 2009
• Part of Java EE 6; Not part of the Web profile!
• Specifies integration with technologies:
– CDI 1.0
– EBJ 3.1
– Servlet 3.0
• Jersey implementation shipped with GlassFish 3.x
• 7 implementations
– Apache CXF, Apache Wink, eXo, Jersey, RESTEasy,
Restlet, Triaxrs

8

Sample JAX-RS application

GlassFish
hello.war
GET /hello/world HTTP/1.1
JAX-RS
resource

HTTP/1.1 200 OK
Content-Type: text/xml
<hello world/>

9

RESTful Application Cycle

Resources are identified by URIs
↓
Clients communicate with resources via requests using a
standard set of methods
↓
Requests and responses contain resource representations
in formats identified by media types
↓
Responses contain URIs that link to further resources

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Resources are identified by URIs

http://example.com/widgets/foo

http://example.com/customers/bar

http://example.com/customers/bar/orders/2

http://example.com/orders/101230/customer

11

JAX-RS Resources
• Resource == Java class
– POJO, EJB Stateless, Singleton Session Beans
– No required interfaces
• ID provided by @Path annotation
– Value is relative URI, base URI is provided by
deployment context or parent resource
– Embedded parameters for non-fixed parts of the URI
– Annotate class or “sub-resource locator” method

12

JAX-RS Resource URIs
@Path("properties")
public class Props {
@GET
List<Prop> getProperties(...) {...}

}

http://.../context/properties

13

JAX-RS Sub-resources

• Root resources can declare sub-resources that will
match the unmatched part of the URI path
• Root resources implement sub-resource locator
methods

14

@Path("properties")

@GET
@Path("{name}")
Prop getProperty(@PathParam("name")String p){…}
}

GET http://.../context/properties/java.home

15

@Path("properties")
@GET
@Path("java.home")
Prop getProperty() {…}

@Path("{name}")
Object getProp(@PathParam("name")String name){
return new Dyna(name); }
}
public class Dyna {
@GET Prop getProperty() {…}
}

16

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

17

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

18

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

19

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

GET http://.../context/properties/java.tmp.dir
20

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

21

@Path("properties")
@GET
@Path("java.home")

@Path("{name}")
}
public class Dyna {
}

22

JAX-RS Sub-resources summary

• Sub-resource classes are processed at runtime
• Warning: easy to confuse sub-resource methods with
sub-resource locators

23

Standard Set of Methods

Method Purpose

GET Read, possibly cached

POST Update or create without a known ID

PUT Update or create with a known ID

DELETE Remove

24

JAX-RS Methods

• Annotate resource class methods with standard method
– @GET, @PUT, @POST, @DELETE, @HEAD
– @HttpMethod meta-annotation allows extensions, e.g.
WebDAV
• JAX-RS routes request to appropriate resource class and
method
• Flexible method signatures, annotations on parameters
specify mapping from request
• Return value mapped to response

25

JAX-RS HTTP Methods

@Path("properties/{name}")

@GET
Prop get(@PathParam("name") String name)
{...}

@PUT
Prop set(@PathParam("name") String name,
String value) {...}

}

26

Resource Representations

• Representation format identified by media type. E.g.:
– XML - application/properties+xml
– JSON - application/properties+json
– (X)HTML+microformats - application/xhtml+xml
• JAX-RS automates content negotiation
– GET /foo
Accept: application/properties+json

27

Resource Representations

• Annotate methods or classes with static capabilities
– @Produces, @Consumes
• Use Variant, VariantListBuilder and
Request.selectVariant for dynamic capabilities
– Also supports language and encoding

28

JAX-RS Resource Representations

@GET
@Produces("application/properties+xml")
Prop getXml(@PathParam("name") String name) {
...
}

@GET
@Produces("text/plain")
String getText(@PathParam("name") String name)
{
...
}

29

JAX-RS Resource Representations

@POST
@Consumes("application/xml")
@Produces({"application/xml","application/json"})
Customer getCustomer(Source id) {
…
return customer;
}

@XmlRootElement
class Customer {
public String first;
public String last;
}

30

Responses Contain Links

HTTP/1.1 201 Created
Date: Wed, 03 Jun 2009 16:41:58 GMT
Server: Apache/1.3.6
Location: http://example.com/properties/foo
Content-Type: application/order+xml
Content-Length: 184

<property self="http://example.com/properties/foo">
<parent ref="http://example.com/properties/bar"/>
<name>Foo</name>
<value>1</value>
</order>

31

• UriInfo provides information about deployment
context, the request URI and the route to the resource
• UriBuilder provides facilities to easily construct URIs
for resources

32


@Context UriInfo i;

SystemProperty p = ...
UriBuilder b = i.getBaseUriBuilder();
URI u = b.path(SystemProperties.class)
.path(p.getName()).build();

List<URI> ancestors = i.getMatchedURIs();
URI parent = ancestors.get(1);

33

The future of JAX-RS

• Possible features in scope for a JAX-RS 2.0 effort
– Client API
– Declarative hyperlinking
– Model View Controller
– Quality of Source
– Form validation
– Asynchronous/Comet/WebSocket
– Improved integration with JSR-330 and @Inject
– JAX-RS Modules

35

Information

• JSR-311: http://jsr311.dev.java.net/
• http://jersey.dev.java.net
• mailto:users@jersey.dev.java.net
• http://glassfish.dev.java.net

36

Servlet
JAX-RS application packaged in WAR like a servlet
For JAX-RS aware containers
web.xml can point to Application subclass
For non-JAX-RS aware containers
web.xml points to implementation-specific Servlet;
and
an init-param identifies the Application subclass
Resource classes and providers can access Servlet
request, context, config and response via injection

38

Java EE

Resource class can be an EJB session or singleton bean
Providers can be an EJB stateless session or singleton
bean
JAX-RS annotations on local interface or no-interface
bean
If JCDI (JSR 299) also supported then
Resource classes can be JCDI beans
Providers can be JCDI beans with application
scope
Full access to facilities of native component model, e.g.
resource injection

39

Introduction to JAX-RS @ SIlicon Valley Code Camp 2010

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