Short introduction to REST

Transcription

1 Short introduction to REST

2 HTTP Hypertext Transfer Protocol HTTP protocol methods: GET, POST, PUT, DELETE, OPTIONS, HEAD HTTP protocol is stateless Server does not know whether this is your first request, and whether this request is yours at all REST 2

3 REST REpresentational State Transfer Introduced and defined in 2000 by Roy Fielding in his PhD htm Fielding developed the REST architectural style in parallel with HTTP 1.1 protocol during REST 3

4 Resource The key abstraction of information in REST is a resource. Any information that can be named can be a resource: a document or image, a temporal service (e.g. "today's weather in Los Angeles"), a collection of other resources, and so on REST 4

5 Resource Representation REST components perform actions on a resource by using a representation to: capture the current or intended state of that resource and transferring that representation between components A representation is: a sequence of bytes, and representation metadata to describe those bytes The data format of a representation is called media type REST 5

6 JSON Example { "book":{ "isbn" : " ", "title" : "Algorithm", "author" : [ "Cormen", "Rivest", "Stein" ], "price" : REST 6

7 REST Constraints (not all) Stateless No client context is being stored on the server between requests. Each request from any client contains all the information necessary to service the request, and session state is held in the client Identification of resources individual resources are identified in requests for example using URIs Resource representation information about resource that is enough to create, modify or delete it REST 7

8 JAX-RS: REST in Java EE JAX-RS: Java API for XML Restful Services JSR 339: 9/index.html Standardizes RESTful Service API for Java EE REST 8

9 REST Application Config import javax.ws.rs.applicationpath; import public class ApplicationConfig extends Application { public Set<Class<?>> getclasses() { return new HashSet<Class<?>>( Arrays.asList( UseCaseController1.class, UseCaseController2.class,... ) ); REST 9

10 Resource (JPA entity + XML + other JPA public class User // and other JPA annotations private long id; private String name; getters/setters REST 10

11 @Produces(MediaType.APPLICATION_XML, ) public class UseCaseController1 private public User find(@pathparam("userid") long id) { User user = em.find(user.class, id); return user; REST 11

12 public User String String String mail) { User user = new User(); user.setfullname(name); user.setpassword(pwd); user.set (mail); em.persist(user); return user; REST 12

13 POST Operation public Response long String String String mail) { User user = em.find(user.class, id); if (user == null) { throw new IllegalArgumentException("user id " + id + " not found"); user.setfullname(name); user.setpassword(pwd); user.set (mail); em.merge(user); return Response.ok(user).build(); // low level API REST 13

14 Resources avimas/library/refcards/refcard-rest.pdf REST 14