javadayiv - leoncini writing restful applications with resteasy
DESCRIPTION
JavaDayIV http://roma.javaday.it/javaday2010Writing Restful Application with RestEasyAndrea Leoncini - Ugo LandiniTRANSCRIPT
Javaday IV – Roma – 30 gennaio 2010
Writing Restful ApplicationsWith RESTEasy
Andrea LeonciniUgo Landini
Javaday IV – Roma – 30 gennaio 2010
Who's Andrea
● Serves as presales & GPS @ Red Hat● Partecipates:
● JBoss User Group Roma (member & sponsor)www.jbugroma.org
● Java User Group Roma (member & proudly cofounder)www.jugroma.it
● JBoss.org
Javaday IV – Roma – 30 gennaio 2010
B42K
● HTTP/1.1● 8 methods, 4 of them (GET,
POST, PUT, DELETE) sufficient to create a Constrained Interface (as well as SQL)
● Ubiquitous, stable● At the same time...
Javaday IV – Roma – 30 gennaio 2010
...Roy Fielding works on REST
● Roy is one of the contributors of the HTTP specification
● He thinks to REST as a key architectural principle of the World Wide Web.
● In other words everything we need to write distributed services is available in the protocol himself
Javaday IV – Roma – 30 gennaio 2010
...and so what?
REST == WWW
SOAP != WWW
REST != SOAP
Javaday IV – Roma – 30 gennaio 2010
What's REST
● REpresentational State Transfer● Is a set of architectural principles or an architectural style● isn’t protocol specific but usually REST == REST + HTTP● It's a different way for writing Web Services● Addressability is the real keyword
Everything should have a URI
Javaday IV – Roma – 30 gennaio 2010
Addressability also means Linkability
● Resource representations have a standardized way of referencing other resource representations
● Representations have a standardized way to compose themselves:
<book id=“123”> <author>http://rs.bookshop.com/authors/345</author> <title>Java Cookbook</title> <abstract> …
Javaday IV – Roma – 30 gennaio 2010
WEB promises, so REST
● Simple● Fast & Scalable● Interoperable● Ubiquitous● Updateable
Javaday IV – Roma – 30 gennaio 2010
Let's start working
● Deploy RESTEasy as web application.● Annotate your classes which have representations you
want to expose.● JAX-RS annotation framework lead by Sun Microsystems – Marc Hadley
● Add annotated classes to the container, RESTEasy has a ServletContextListener to initialize the registry of your services (you can programmatically interact with it).
Javaday IV – Roma – 30 gennaio 2010
Using @Path
● @Path("/library") associates a URI to your representation
● Both class and methods must have @Path annotation
● URI is the concatenation of class and method
● You don't need to annotate a method you are mapping with the class @Path
@Path("/library")public class Library {
@GET @Path("/books") public String getBooks() {...}
[...] }
Javaday IV – Roma – 30 gennaio 2010
Using @Path
● @Path("/library") associates a URI to your representation
● Both class and methods must have @Path annotation
● URI is the concatenation of class and method
● You don't need to annotate a method you are mapping with the class @Path
@Path("/library")public class Library {
@GET @Path("/books") public String getBooks() {...}
[...] }
http://www.therestserver.org/rs/library/books
Javaday IV – Roma – 30 gennaio 2010
Using HTTP Methods
● @GET, @POST, @PUT and @DELETE4 methods for a CRUD environment, isn't it?
● As well as SQL
● But don't forget @HEAD
Javaday IV – Roma – 30 gennaio 2010
Ok, what about parameters?
● @PathParam enables you to map variables from URL to your method
@Path("/library")public class Library {
@GET @Path("/book/{isbn}") public String getBook(@PathParam("isbn") ISBN id) {...}
[...] }
Javaday IV – Roma – 30 gennaio 2010
Ok, what about parameters?
● @PathParam enables you to map variables from URL to your method
@Path("/library")public class Library {
@GET @Path("/book/{isbn}") public String getBook(@PathParam("isbn") ISBN id) {...}
[...] }
http://www.therestserver.org/rs/library/book/357
Javaday IV – Roma – 30 gennaio 2010
Do we have other ways?
● Use @QueryParam to specify parameters on QueryString of the URL
● Or @HeaderParam to access the HTTP header
Javaday IV – Roma – 30 gennaio 2010
Do we have other ways?
● Use @QueryParam to specify parameters on QueryString of the URL
● Or @HeaderParam to access the HTTP header
@GET @Path("/used") public String getUsedCars(@QueryParam("min") int min, @QueryParam("max") int max) {...}
Javaday IV – Roma – 30 gennaio 2010
Do we have other ways?
● Use @QueryParam to specify parameters on QueryString of the URL
● Or @HeaderParam to access the HTTP header
@GET @Path("/used") public String getUsedCars(@QueryParam("min") int min, @QueryParam("max") int max) {...}
@GET @Path("/books") public String getBooks(@HeaderParam("From")String requestFrom) {...}
Javaday IV – Roma – 30 gennaio 2010
Do we have other ways?
● Use @QueryParam to specify parameters on QueryString of the URL
● Or @HeaderParam to access the HTTP header
@GET @Path("/used") public String getUsedCars(@QueryParam("min") int min, @QueryParam("max") int max) {...}
http://www.therestserver.org/rs/carshop/used?min=30000&max=40000
@GET @Path("/books") public String getBooks(@HeaderParam("From")String requestFrom) {...}
Javaday IV – Roma – 30 gennaio 2010
And not only...
● You can exchange parameters also with:● @CookieParam● @FormParam● @Form (RESTEasy specific)● @Encoded
Javaday IV – Roma – 30 gennaio 2010
And don't forget...
● With both paths and parameters you can useregular expressions
● For every parameter you can specify a primitive, a string or a class with a String constructor or static valueof() method
Javaday IV – Roma – 30 gennaio 2010
HTTP Content Negotiation
● Which type of objects can my clients obtain or my server receive?
● The HTTP protocol has built-in content negotiation headers that allow the client and server to specify the type of content that they transfer, and the type of content they prefer to receive.
● On the server side we can specify content preferences using @Produces and @Consumes annotations
Javaday IV – Roma – 30 gennaio 2010
Using @Produces
● @Produces is used to map a client request and match it with the client's Accept header.
● The Accept HTTP header is sent by the client, and defines the media types that the client prefers to receive from the server
@Path("/library")@Produces("text/*")public class Library {
@GET @Path("/books") @Produces("text/xml") public String getXMLBooks() { return “<books>An xml list of books</books>”; }
@GET @Path("/books") @Produces("text/plain") public String getBooks() { return “a list of books”; } }
Javaday IV – Roma – 30 gennaio 2010
Using @Consumes
● @Consumes is used to specify a set of media types a resource can consume with its methods
● The client makes a request with content-type header parameter
● Then the server invokes the method that matches the media type indicated by the client
@Path("/bookshop")@Consumes("text/*")public class Library {
@POST @Path("/order") @Consumes("application/xml") public void addBookToBasket(Book xmlBook) { ... } }
Javaday IV – Roma – 30 gennaio 2010
Using Cache Annotations
● @Cache and @NoCache enables you to set the Cache-Control headers on a successful GET request, that is any any request that returns a 200 OK response.
● It can be used only on GET annotated methods.
● @Cache annotation builds the Cache-Control header, @NoCache actually sets Cache-Control: nocache.
● If (and only if) you have specified a Cache annotation on your method server side implementation of RESTEasy checks to see if the URL has been already served. If it does it uses the already marshalled response without invoking the method.
Javaday IV – Roma – 30 gennaio 2010
ATOM support
● RESTEasy supports ATOM● What is ATOM?
● XML doc for listing related information, AKA feeds.It is primarily used to syndicate the web
● ATOM is very likely the RSS feed of the next generation● Used with REST can be considered as a simplyfied
envelope
Javaday IV – Roma – 30 gennaio 2010
ATOM support
● RESTEasy supports ATOM● What is ATOM?
● XML doc for listing related information, AKA feeds.It is primarily used to syndicate the web
● ATOM is very likely the RSS feed of the next generation● Used with REST can be considered as a simplyfied
envelope
@Path("/feeder")public class Feeder {
@GET @Path("/entry") @Produces("application/atom+xml") public Entry getEntry() Entry entry = new Entry(); entry.setTitle("Hi mr president"); Content content = new Content(); content.setJAXBObject(new Customer("Ugo")); ... return entry;}
Javaday IV – Roma – 30 gennaio 2010
Next Steps
● Hands On Lab with JBosstwo hours step by step session for a real use case, including Providers and Cache, so...stay tuned... www.it.redhat.com/events/
● http://www.jboss.org/resteasyDownload, unzip, run, code, debug, deploy, enjoy
● http://jsr311.dev.java.net/JAX-RS
18 marzo a Roma25 marzo a Milano
