Creating a Web of Data with Restlet

Creating a Web of Data with Restlet Andrew Newman Monday, 8 December 2008 1

REST Architecture Resource Oriented Analysis and Design (ROAD) Stateless Access Where Everything is a Resource Identiﬁed by URI With Different Representations Linked Together Monday, 8 December 2008 2

Restlet Oveview GWT, Client and Server APIs Standalone, App Servers, Oracle, OSGi, Spring HTTP, SMTP, POP3, JDBC, File Connectors JSON, XML, HTML, Atom Representations Integration with Groovy, JPA, Seam, Struts Hibernate Monday, 8 December 2008 3

A little bit of HTTP Verb Action GET Return the entity POST Server create/modify entity PUT Client create/modify entity DELETE X Delete an entity HEAD Entity metadata (not data) OPTIONS ? Methods supported on entity Monday, 8 December 2008 4

Restlet Model Uniform Restlet Application Component Redirector Connector Router Filter Finder Client Server Guard Route Transformer Monday, 8 December 2008 5

Restlet Model • Reference - Mutable java.net.URI • Request - Client Request • Response - Server Response • MediaType - Mime Types e.g. text/html, application/xml • Resource - Anything with a Reference e.g. video, document, collection • Variant - Metadata about a representation. • Representation - The current state/value of a Resource. Monday, 8 December 2008 6

Resource API GET Representation represent(Variant) POST void acceptRepresentation(Representation) PUT void storeRepresentation(Representation) DELETE void removeRepresentations() HEAD Calls GET without stream. OPTIONS Updates Response’s getAllowedMethods Monday, 8 December 2008 7

Applications and Components // Create Application for http://localhost/helloWorld Application application = new Application() { public synchronized Restlet createRoot() { Router router = new Router(getContext()); // Attach a resource router.attach(quot;helloWorldquot;, HelloWorldResource.class); return router; } }; // Create the component and attach the application Component component = new Component(); component.getServers().add(Protocol.HTTP); component.getDefaultHost().attach(application); // Start the web server component.start(); Monday, 8 December 2008 8

Data and Resources public HelloWorldResource(Context context, Request request, Response response) { super(context, request, response); // Declare all kind of representations supported by the resource getVariants().add(new Variant(MediaType.TEXT_PLAIN)); } // Respond to GET public Representation represent(Variant variant) throws ResourceException { Representation representation = null; // Generate a representation according to the variant media type. if (MediaType.TEXT_PLAIN.equals(variant.getMediaType())) { representation = new StringRepresentation(quot;hello, worldquot;, MediaType.TEXT_PLAIN); } return representation; } Monday, 8 December 2008 9

A Bit More HTTP GET /index HTTP/1.1 Host: www.realestate.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: 1.7.12)... Accept: text/xml,application/xml,application/xhtml +xml,text/html;q=0.9,... Accept-Language: us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-15,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive Monday, 8 December 2008 10

Drop the Dot Yes http://realestate.com/house/1 + type No http://realestate.com/house/1.html http://realestate.com/house/1.xml http://realestate.com/house/1.json http://realestate.com/house/1.png Monday, 8 December 2008 11

No iPhone Yes http://realestate.com/house/1 + user-agent No http://www.realestate.com/house/1 http://iphone.realestate.com/house/1 http://iphone-v2.realestate.com/house/1 http://n95-8GB-Black.realestate.com/house/1 Monday, 8 December 2008 12

Client Side API // GET a resource from uri as a XML DOM. Response response = new Client(Protocol.HTTP).get(uri); DomRepresentation document = response.getEntityAsDom(); // Specify content types. ClientInfo clientInfo = request.getClientInfo(); List<Preference<MediaType>> preferenceList = new ArrayList<Preference<MediaType>>(); preferenceList.add(new Preference<MediaType>(TEXT_XML)); preferenceList.add(new Preference<MediaType>(APPLICATION_XML)); preferenceList.add(new Preference<MediaType>(APPLICATION_XHTML_XML)); preferenceList.add(new Preference<MediaType>(TEXT_HTML, 0.9f)); clientInfo.setAcceptedMediaTypes(preferenceList); // Specify encodings clientInfo.setAcceptedEncodings(Arrays.asList(new Preference<Encoding>(Encoding.GZIP)); // Finally, GET. client.get(uri); Monday, 8 December 2008 13

Simple WebDAV Directory Demo See also: http://code.google.com/p/gogoego/ Monday, 8 December 2008 14

Restlet and Spring ConﬁgurableRestletResource <bean id=quot;someResourcequot; class=quot;SomeResourcequot; scope=quot;prototypequot;> <property name=quot;representationTemplatesquot;> <map> <entry key-ref=quot;TEXT_HTMLquot; value-ref=quot;htmlRepquot;/> <entry key-ref=quot;APPLICATION_JSONquot; value-ref=quot;jsonRepquot;/> <entry key-ref=quot;APPLICATION_XMLquot; value-ref=quot;xmlRepquot;/> </map> </property> </bean> Monday, 8 December 2008 15

Restlet and Spring FreemarkerRepresentationFactory <bean id=quot;htmlRepquot; class=quot;org.jrdf.query.server.FreemarkerRepresentationFactoryquot;> <property name=quot;templateNamequot; value=quot;dbLocal-html.ftlquot;/> <property name=quot;freemarkerConfigquot; ref=quot;freemarkerConfigquot;/> </bean> dbLocal-html.ftl <html> <head> <title>Query Page -- Database ${database}</title> </head> <body> <h1> Query for database <i>${database}</i> ... Monday, 8 December 2008 16

Restlet and Spring SpringRouter <bean id=quot;routerquot; class=quot;org.restlet.ext.spring.SpringRouterquot;> <property name=quot;attachmentsquot;> <map> <entry key=quot;/databasesquot;> <bean class=quot;org.restlet.ext.spring.SpringFinderquot;> <lookup-method name=quot;createResourcequot; bean=quot;listDbResourcequot;/> </bean> </entry> <entry key=quot;/databases/{database}quot;> <bean class=quot;org.restlet.ext.spring.SpringFinderquot;> <lookup-method name=quot;createResourcequot; bean=quot;queryDbResourcequot;/> </bean> </entry> </map> </property> </bean> Monday, 8 December 2008 17

Restlet and Spring public Representation represent(Variant variant) { Representation rep = null; try { graphName = (String) getRequest().getAttributes().get(quot;databasequot;); if (getRequest().getResourceRef().hasQuery()) { queryString = getRequest().getResourceRef().getQueryAsForm(). getFirst(quot;queryquot;).getValue(); } if (queryString == null) { rep = queryPageRepresentation(variant); } else { rep = queryResultRepresentation(variant); } getResponse().setStatus(SUCCESS_OK); } catch (Exception e) { getResponse().setStatus(SERVER_ERROR_INTERNAL, e, e.getMessage().replace(quot;nquot;, quot;quot;)); } return rep; } Monday, 8 December 2008 18

Linking Data MyFood.Com YourFood recipe recipe ID Desc. Cat. ID Desc. Cat. 1 Chips Snack 1 Toast Snack 2 Ice Water Drink 2 Tea Drink URIs URIs http://myfood.com/recipe/chips http://yourfood.com/recipe/toast http://myfood.com/recipe/water http://yourfood.com/recipe/tea http://myfood.com/cat/snack http://yourfood.com/cat/snack http://myfood.com/cat/drink http://yourfood.com/cat/drink Monday, 8 December 2008 19

Linking Data ? MyFood.Com YourFood recipe recipe ID Desc. Cat. ID Desc. Cat. 1 Chips Snack 1 Toast Snack 2 Ice Water Drink 2 Tea Drink URIs URIs http://myfood.com/recipe/chips http://yourfood.com/recipe/toast http://myfood.com/recipe/water http://yourfood.com/recipe/tea http://myfood.com/cat/snack http://yourfood.com/cat/snack http://myfood.com/cat/drink http://yourfood.com/cat/drink Monday, 8 December 2008 20

Linking Data http://myfood.com/cat/snack http://yourfood.com/cat/snack IsA IsA http://myfood.com/recipe/chips http://yourfood.com/recipe/toast Monday, 8 December 2008 21

Linking Data http://myfood.com/cat/snack isTheS ameA s http://yourfood.com/cat/snack IsA IsA http://myfood.com/recipe/chips http://yourfood.com/recipe/toast Monday, 8 December 2008 22

Linking Data http://myfood.com/cat/snack isTheS ameA s http://yourfood.com/cat/snack IsA IsA http://myfood.com/recipe/chips IsA IsA http://yourfood.com/recipe/toast http://purl.org/recipe Monday, 8 December 2008 23

Querying the Web User at myFood.Com wants all the snack recipes: 1. Find all http://purl.org/recipe and http://myfood.com/cat/snack recipe {my:chips, my:water}, snack {my:snack} 2. my:snack = your:snack 3. Query YourFood recipe {your:toast, your:tea}, snack {your:tea} 4. Answer: {my:chips, your:toast} Monday, 8 December 2008 24

How do you Link Data? RDF (Linking URIs) <my:chips> <rdfs:type> <purl:snack> SPARQL (Querying) SELECT * FROM myfood, yourfood WHERE { ?recipe <rdfs:type> <purl:recipe> . ?recipe <rdfs:type> <my:cat/snack> } OWL (Adding Relationships) <my:cat/snack> <owl:sameAs> <your:cat/snack> Monday, 8 December 2008 25

Questions? Monday, 8 December 2008 26

Creating a Web of Data with Restlet

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