introduction to jax-rs @ silicon valley code camp 2010

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Introduction to JAX-RS Jitendra Kotamraju

Oct 2010

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What this presentation is about ?

• Not the REST style per se– But, briefly ...

• The basics of JAX-RS

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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

©2010 Oracle Corporation

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Very Short REST Primer:Buy This Book


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REST is an Architectural Style

Set of constraints you apply to the architecture of a distributed system

to induce desirable properties


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RESTful Web Services

Application of REST architectural style to services that utilize Web standards (URIs, HTTP, HTML,

XML, Atom, RDF etc.)

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Java API for RESTful Web Services (JAX-RS)

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

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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

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Sample JAX-RS application

GlassFish

hello.war

JAX-RSresource

GET /hello/world HTTP/1.1

HTTP/1.1 200 OKContent-Type: text/xml

<hello world/>

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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

RESTful Application Cycle

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http://example.com/widgets/foo

http://example.com/customers/bar

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

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

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


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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


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JAX-RS Resource URIs

@Path("properties")public class Props { @GET List<Prop> getProperties(...) {...}

}

http://.../context/properties

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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


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@Path("properties")public class Props { @GET @Path("{name}") Prop getProperty(@PathParam("name")String p){…}}

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


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

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


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


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JAX-RS Sub-resources summary

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

sub-resource locators

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Standard Set of Methods

PurposeMethod

RemoveDELETE

Update or create with a known IDPUT

Update or create without a known IDPOST

Read, possibly cachedGET

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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


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@Path("properties/{name}")public class Props {

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

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

}

JAX-RS HTTP Methods

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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 /fooAccept: application/properties+json

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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

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

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

JAX-RS Resource Representations

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

@XmlRootElementclass Customer { public String first; public String last;}

JAX-RS Resource Representations

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Responses Contain Links

HTTP/1.1 201 CreatedDate: Wed, 03 Jun 2009 16:41:58 GMTServer: Apache/1.3.6Location: http://example.com/properties/fooContent-Type: application/order+xmlContent-Length: 184

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

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• UriInfo provides information about deployment context, the request URI and the route to the resource

• UriBuilder provides facilities to easily construct URIs for resources


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@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);

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Demos

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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

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Information

• JSR-311: http://jsr311.dev.java.net/• http://jersey.dev.java.net• mailto:[email protected]• http://glassfish.dev.java.net

http://jsr311.dev.java.net/

http://jersey.dev.java.net/

mailto:[email protected]

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Questions ?


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ServletJAX-RS application packaged in WAR like a servlet

For JAX-RS aware containersweb.xml can point to Application subclass

For non-JAX-RS aware containersweb.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

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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 thenResource 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

introduction to jax-rs @ silicon valley code camp 2010

Technology

jaxrs resources resource

jaxrs methods

jaxrs api

jaxrs resourcehttp1

jaxrs resource uris

public class dyna

home prop getproperty

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