Introduction to JAX-RS

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Andreas Bjärlestam

mailto:andreas@bjarlestam.com

http://andreas.bjarlestam.com

http://twitter.com/bjarlestam

REST? Attribution: http://www.flickr.com/photos/noahbulgaria/270090287

Pragmatic explanation

Use HTTP the way it was designed to be used

Take advantage of the good things in HTTP

By following a set of constraints

Constraints in REST

Give everything its own URI

Communicate with a standard set of methods

Communicate with Media Types

Link your resources together

Avoid session state

Support caching

* This is a very simplified version of the real REST constraints, for the real stuff read Roy Fieldings dissertation

JAX-RS (JSR 311)

Java API for building RESTful services

JAX-RS

Based on POJOs with Annotations

JAX-RS

Makes the developer focus on URLs, HTTP methods and Media Types.

Lets code…

@Path

@Path( "location" )

public class LocationResouce {

}

@GET, @PUT, @POST

@Path( "location" )

@GET

@Produces( "application/xml" )

public String getLocation() {

return "<location>I’m in Sweden</location>" ;

}

}

curl

@PathParam, @QueryParam

@Path( "location" )

@GET

@Path( "{user}" )

public String getLocation(@PathParam( "user" ) String user) {

return "<location>” + user + " is in Sweden</location>" ;

}

}

JAXB

@Path( "location" )

@GET

@Path( "{user}" )

public Location getLocation(@PathParam( "user" ) String user) {

return new Location( "59.3" , "18" );

}

}

JAXB

@XmlRootElement

public class Location {

public String lattitude;

public String longitude;

public Date timestamp;

. . .

}

@Produces and Media Types

@Path( "location" )

@GET

@Path( "{user}" )

@Produces({ "application/xml", "application/json" })

public Location getLocation(@PathParam( "user" ) String user) {

return new Location( "59.3" , "18" );

}

}

@Context, UriInfo and UriBuilder

@Path( "location" )

@Context UriInfo uriInfo;

. . .

@POST

@Consumes( "application/x-www-form-urlencoded" )

public Response saveLocation(@FormParam( "user" ) String user) {

locations.put (user, new Location( "59.3" , "18" ));

UriBuilder uriBuilder = uriInfo .getAbsolutePathBuilder();

URI userUri = uriBuilder.path(user).build();

return Response.created(userUri).build();

}

}

Cache Control

@GET

@Path( "{user}" )

@Produces({ "application/xml", "application/json" })

public Response getLocation(@PathParam( "user" ) String user) {

Location l = locations .get(user);

CacheControl cc = new CacheControl();

cc.setMaxAge(500);

Response.ResponseBuilder builder = Response.ok(l);

builder.cacheControl(cc);

return builder.build() ;

}

For the interested

Roy Fieldings PhD dissertation, see ch 5

http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm

Roy Fieldings blog

http://roy.gbiv.com/untangled/

Mark Hadleys blog

http://weblogs.java.net/blog/mhadley/

Mark Nottinghams blog

http://www.mnot.net

Stefan Tilkovs blog

http://www.innoq.com/blog/st/

Extra slides

JAX-RS

JSR 311

Version 1.0 was finalized in september 2008

Version 1.1 is planned to be part of JEE6

JAX-RS

Several implementations available

Sun Jersey

JBoss RestEasy

Restlets

Apache CXF

Triaxrs

Apache WINK

Serendipity

By giving everything a URL, sticking to a Uniform Interface and linking your resources you make the chances of reuse in unexpected ways higher

Statelessness

Better scaling

No session storage on server

Any server in a cluster can handle any request

The resources can safely be cached

More reliable

A client can safely re-send a request

Better resource reuse

The resources can safely be linked to

Caching

Client Proxy Cache Client Client Server Proxy Cache Client Reverse Proxy Cache Client Cache Client Cache Client Cache Client Cache

“ The best requests are those that not even reach me.” - Anonymous overloaded Server

50 requests/second = 3000 requests/minute setting max-age=60 (seconds) can then save you 2999 requests

Caching

GET can be cached while POST can't (safely)

Specify max-age

Use max-age cache control header

Split data according to freshness requirement

Support conditional GET

Get if modified since

E-tags

Introduction to JAX-RS

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