Java Web Services [5/5]: REST and JAX-RS
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This document discusses Representational State Transfer (REST) and the Java API for RESTful Web Services (JAX-RS). It defines REST as an architectural style for distributed hypermedia systems that specifies resources be identified in requests using URIs and manipulated using representations and standard HTTP methods. It outlines how JAX-RS allows developing RESTful web services using Java by treating classes as resources identified with URIs and HTTP methods mapped to class methods using annotations. Major implementations of JAX-RS are also listed.
![REST : Definition [Wikipedia]
Representational State Transfer
a style of software architecture for distributed
hypermedia systems such as the World Wide
Web.
was introduced and defined in 2000 by Roy
Fielding in his doctoral dissertation.
Conforming to the REST constraints is referred
to as being ‘RESTful’.
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Java Web Services [5/5]: REST and JAX-RS
- 1. Topic 5 REST and JAX-RS Assoc.Prof. Dr. Thanachart Numnonda www.imcinstitute.com August 2010
- 2. Agenda What is REST? REST/HTTP Methods JAX-RS 2
- 3. What is REST? 3
- 4. REST : Definition [Wikipedia] Representational State Transfer a style of software architecture for distributed hypermedia systems such as the World Wide Web. was introduced and defined in 2000 by Roy Fielding in his doctoral dissertation. Conforming to the REST constraints is referred to as being ‘RESTful’. 4
- 5. REST is ... An architectural style, not technology – Client/server + Request/response approach. Everything is a RESOURCE. CRUD (Create / Read / Update / Delete) Stateless by nature (excellent for distributed systems) Cacheable (naturally supported !) A great way to web-service ! 5
- 10. Everything is a resource … A resource is … – A network-accessible data object or service identified by an URI: – Images, – Documents (HTML, PDF, …), – Geo-location, – Weather 10
- 11. Resource Collections – http://portal/books/ Members/Items: – http://portal/documents/mybook.doc 11
- 12. Characteristics of REST RESTful services are stateless – Each request from client to server must contain all the information necessary to understand the request RESTful services have a uniform interface – GET, POST, PUT, and DELETE. REST-based architectures are built from resources (pieces of information) that are uniquely identified by URIs – In a RESTful purchasing system, each purchase order has a unique URI 12
- 13. Characteristics of REST REST components manipulate resources by exchanging representations of the resources – For example, a purchase order resource can be represented by an XML document. – Within a RESTful purchasing system, a purchase order might be updated by posting an XML document containing the changed purchase order to its URI REST-based architectures communicate primarily through the transfer of representations of resources – State is maintained within a resource representation 13
- 14. REST/HTTP Methods 14
- 15. CRUD to HTTP method mapping 15
- 16. CRUD Operations are Performed through “HTTP method”+“Resource” CRUD Operations HTTP method Resource Create (Single) POST Collection URI Read (Multiple) GET Collection URI Read (Single) GET Entry URI Update (Single) PUT Entry URI Delete (Single) DELETE Entry URI 16
- 17. HTTP Methods /books/ – POST - submit a new book – GET - list all books /books/{isbn}/ – GET - get a book – PUT - update a book – DELETE - remove a book 17
- 18. HTTP Methods: GET GET to retrieve information Retrieves a given URI Idempotent, should not initiate a state change Cacheable 18
- 19. HTTP Methods: POST POST to add new information add the entity as a subordinate/append to the POSTed resource Example – POST /music/beatles Adds the music specified in the POSTDATA to the list of music 19
- 20. HTTP Methods: DELETE Remove (logical) an entity Example – DELETE /songs/heyjude Delete the song 'heyjude” from the system 20
- 21. HTTP Methods: POST POST to add new information add the entity as a subordinate/append to the POSTed resource Example – POST /music/beatles Adds the music specified in the POSTDATA to the list of music 21
- 22. Why REST ? • Uniformity: – URI is a uniform way to identify resources – HTTP uniform interface to manipulate resources • REST base services are easy to work with – Do not need specialized API, just need to understand HTTP and browser for experimentation • Scripting language friendly – Easy to consume and develop 22
- 23. Advantages of REST • Its architectural constraints when applied as a whole, generate: – Scalable component interactions – General interfaces – Independently deployed connectors – Reduced interaction latency – Strengthened security – Safe encapsulation of legacy systems 23
- 24. REST vs “Big” Web Services • “Big” web service – Few URIs (nouns), many custom methods (verbs) • musicPort.getRecordings(“beatles”) – Uses HTTP as transport for SOAP messages • RESTful web service – Many resources (nouns), few fixed methods(verbs) • GET /music/artists/beatles/recordings – HTTP is the protocol 24
- 25. JAX-RS 25
- 26. JAX-RS (JSR-311) : Goals • POJO-based, • HTTP-centric, • Format independent, • Container independent, • Availability as standalone and enterprise platforms. 26
- 27. JAX-RS: Address-ability through URI • A Web service exposes data as resources • A resource is exposed through a URI • Resources are “plain old” Java classes and methods • The annotation @Path exposes a resource • Think resources and URIs using Java classes and @Path 27
- 28. POJO + Annotation = JAX-RS resource 28
- 29. Reading the catalog 29
- 30. Reading the catalog item 30
- 31. Address-ability through HTTP Methods • Methods: what are the HTTP methods? • HTTP methods implemented as Java methods annotated with – @POST – @GET – @PUT – @DELETE 31
- 32. Uniform interface: methods on root resources @Path(“/books/”) class books { @POST <type> create(<type>) { ... } @GET <type> get() { ... } } @Path(“/books/{isbn}/”) class book { @GET <type> get(...) { ... } @PUT void update(...) { ... } @DELETE void delete(...) { ... } } Java method name is not significant The HTTP method is the method 32
- 33. Leading JAX-RS implementations • Glassfish Jersey project • RESTEasy(JBoss) • Apache CXF (Apache Software Foundation) • Wink (ASF incubation project) • Restlet(NoeliosTechnologies) 33
- 34. Resources Some contents are borrowed from the presentation slides of Sang Shin, Java™ Technology Evangelist, Sun Microsystems, Inc. JAX-RS… and the REST will follow, Guy Nir, Java Edge 09 34
- 35. Thank you [email protected] www.facebook.com/imcinstitute www.imcinstitute.com 35