A description of REST, using RESTlet and linking data together from different web sites.

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

2. REST Architecture
Resource Oriented Analysis and Design (ROAD)
Stateless Access
Where Everything is a Resource
Identified by URI
With Different Representations
Linked Together
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3. 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
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4. 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
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5. Restlet Model
Uniform
Restlet
Application Component Redirector
Connector Router Filter Finder
Client Server Guard Route
Transformer
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6. 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.
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7. 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
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8. 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();
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9. 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;
}
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10. 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
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11. 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
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12. 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
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13. 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);
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14. Simple WebDAV
Directory Demo
See also: http://code.google.com/p/gogoego/
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15. 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>
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16. 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>
...
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17. 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>
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18. 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;
}
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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
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20. 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
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21. Linking Data
http://myfood.com/cat/snack
http://yourfood.com/cat/snack
IsA
IsA
http://myfood.com/recipe/chips
http://yourfood.com/recipe/toast
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22. 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
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23. 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
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24. 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}
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25. 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>
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26. Questions?
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