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REST ( RE presentational S tate T ransfer)

REST ( RE presentational S tate T ransfer). 2012. 10 Youn-Hee Han LINK@KOREATECH http://link.koreatech.ac.kr. REST 의 개념 이해. What is REST?. REST (Representational State Transfer) 대규모 네트워크 시스템을 위한 설계패턴 또는 아키텍처 웹을 기반으로 하는 대규모 네트워크 시스템 설계 및 구현을 위한 일종의 원칙들의 모음

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REST ( RE presentational S tate T ransfer)

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  1. REST(REpresentational State Transfer) 2012. 10 Youn-Hee Han LINK@KOREATECH http://link.koreatech.ac.kr

  2. REST의개념 이해 LINK@KOREATECH

  3. What is REST? • REST (Representational State Transfer) • 대규모 네트워크 시스템을 위한 설계패턴 또는 아키텍처 • 웹을 기반으로 하는 대규모 네트워크 시스템 설계 및 구현을 위한 일종의 원칙들의 모음 • 2000년 Roy Fielding의 박사 학위 논문에서 처음 제안. • Architectural Styles and the Design of Network-based Software Architectures (DOCTOR OF PHILOSOPHY) • http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm • 최근 추가된 뜻 • XML과 HTTP를 사용하는 단순한 웹 기반 인터페이스를 지칭(즉, REST의 원칙을 따르는 Web Services) LINK@KOREATECH

  4. What is REST? • 왜 Representational State Transfer 이라고 명칭을 붙였나? All Resources on WEB are represented as XML by URL(Representation) CLICK URL 표현(다른 URL 포함) Representational State Transfer은 잘 디자인된 웹 어플리케이션이 어떻게 동작하는 지에 대한 이미지를 떠올리게 하기 위한 용어이다. 즉 웹을 거대한 Virtual State Machine이라고 생각하면 우리는 그 웹의 상태를 XML등으로 표현된 것으로 확인할 수 있고 그 전에 알고 있던 또는 XML에 포함된 링크를 선택/호출함으로써 Machine내에 존재하는 State가 전이되고 새로운 표현 (New State Representation)이 보여지게 된다 LINK@KOREATECH

  5. What is REST? • 좀 더 현실적인 REST의 설명 • Web Service를 구현하는 기존 방식인 SOAP, XML-RPC보다 매우 간단 • 최근 Open API 구현에 많이 사용 • 많은 웹2.0 회사들이 Open API의 구현 방법으로 많이 사용. • 구글, 플리커, 아마존 등의 Open API가 REST 방식으로 구현되어 공개 • 서비스의 서버 플랫폼 구축에 있어 필수적인 아키텍쳐로 인식됨 • REST는 실제 표준은 아니지만 HTTP/URL/MIME Type같은 웹 표준만을 사용 • 구글이오랫동안 제공해온 SOAP 기반 검색 API서비스가 2006년 12월 5일 부로 중단 • 대신 구글은 REST 기반의 Ajax Search API를 대안으로 제시 LINK@KOREATECH

  6. What is REST? • REST is not a standard • You will not see the W3C REST specification. • You will not see IBM or Microsoft or Sun selling a REST developer's toolkit. • REST is just a design pattern • You can only understand it and design your Web services according to its rules. • REST does prescribe the use of standards: • HTTP • URL • XML/HTML/JSON/GIF/JPEG/etc.(Resource Representations) • text/xml, text/html, image/gif, image/jpeg, etc. (Resource Types, MIME Types) LINK@KOREATECH

  7. What is REST? • REST의성공 요인 • 상태를 유지하지 않는 (Stateless) 클라이언트/서버 구조를 가진다. • 작고 어디에서나 적용되는 인터페이스를 가진다. • GET, POST, PUT, DELETE • PUT과 DELETE 메소드는 HTTP스펙에는 존재하지만 지원하는 브라우저는 거의 없다. • 모든 자원은 URL를 이용하여 유일하게 지칭될 수 있다. • 자원들의 표현(Representation)들이 URL을 통해 서로 연결되어 있다. • REST의 원칙에는 쿠키나 세션을 사용하지 않는다. LINK@KOREATECH

  8. CRUD Operations in REST • URL을 통해 필요한 자원을 계속해서 추적하여… • 얻어(GET) 가거나 • 생성(POST) 하거나 • 삽입(PUT) • 삭제(DELETE) 할 수 있게 분류 설계한다. • CRUD/HTTP 사이의 대응 • 전체 시스템은 단지 다음 4개의 명령을 사용해서만 동작한다. LINK@KOREATECH

  9. REST vs. RPC (Remote Procedure Call)-style • REST vs RPC-style (Java RMI, CORBA, DCOM, SOAP…) • REST URL • 서버 주소/서비스 이름/자원 • Examples • 잘 된 구성 - http://wisefree.com/employee/603045 (O) • 잘못 된 구성 - http://wisefree.com/employee/getEmployee?id=603045 (X) LINK@KOREATECH

  10. Web Design, Axiom 0(Tim Berners-Lee, director of W3C) • Axiom 0: all resources on the Web must be uniquely identified with a URI. resource1 URL1 resource2 URL2 resource3 URL3 LINK@KOREATECH

  11. Example1: Airline Reservation Service • The airline wants to ensure that its premier members get immediate service, its frequent flyer members get expedited service and all others get regular service • There are two main approaches to implementing the reservation service… LINK@KOREATECH

  12. Approach 1 • "Press 1 for Premier, Press 2 for…“ • The airline provides a single telephone number. • Upon entry into the system a customer encounters an automated message, "Press 1 if you are a premier member, press 2 if you are a frequent flyer, press 3 for all others." Premier Customer Representative Premier Members F.F. Customer Representative Answering Machine Airline Reservations Frequent Flyer Members Regular Customer Representative Regular Members LINK@KOREATECH

  13. Approach 2 • " Telephone Numbers are Cheap! Use Them!” • The airline provides several telephone numbers - one number for premier members, a different number for frequent flyers, and still another for regular customers. Premier Customer Representative 1-800-Premier Premier Members F.F. Customer Representative 1-800-Frequent Frequent Flyer Members Regular Customer Representative 1-800-Reservation Regular Members LINK@KOREATECH

  14. Approach 2: URLs are Cheap! Use Them! The airline provides several URLs - one URL for premier members, a different URL for frequent flyers, and still another for regular customers. Premier Member Reservation Service http://www.kings-air/reservations/premier client Premier Members Frequent Flyer Reservation Service http://www.kings-air/reservations/frequent-flyer client Frequent Flyer Members Regular Member Reservation Service http://www.kings-air/reservations/regular client Regular Members LINK@KOREATECH

  15. Approach 2 Advantages • The different URLs are discoverable by search engines and UDDI registries. • It's easy to understand what each service does simply by examining the URL. • There is no need to introduce rules. • Priorities are elevated to the level of a URL. • "What you see is what you get." • It's easy to implement high priority • simply assign a fast machine at the premier member URL. • There is no bottleneck. • There is no central point of failure. • Consistent with Axiom 0. LINK@KOREATECH

  16. Three Fundamental Aspects of the REST Design Pattern • Resources • Every distinguishable entity is a resource. • A resource may be a Web site, an HTML page, an XML document, or a Web service, etc. • URL can identify Resources • Every resource is uniquely identified by a URL. • This is Tim Berners-Lee Web Design, Axiom 0. • CRUD operations Resources URLs Simple Operations (CRUD) LINK@KOREATECH

  17. REST 방식의 웹서비스 구현 및 실습 LINK@KOREATECH

  18. REST 구현 방법 • 방법 1] Restlet 라이브러리 사용 • 자바를 위한 경량화 REST framework • 오픈소스 프로젝트 • 서블릿의 프로그래밍 모델을 기반 • JSR (Java Specification Requests) 311 • Java API for RESTful Web Services (이하 JSR 311) • Restlet 홈페이지 • http://www.restlet.org • 방법 2] Java EE에서 지원하는 REST 라이브러리 사용 • JAX-WS (Java API for XML Web Services) 라이브러리 • XML과 웹 서비스 관련 API • JAX-WS의 핵심은 SOAP-WSDL이여서 그다지 쓰이지 않았음. • JAX-WS2에서 HTTP바인딩과 함께 REST 지원 LINK@KOREATECH

  19. REST 구현 방법 • RESTlet 라이브러리설치 • http://www.restlet.org/downloads/stable (version 2.0.15) • Editionfor Java SE • D 드라이브의 특정 폴더에 압축 해제 LINK@KOREATECH

  20. REST 구현 방법 • RESTlet 소스를 저장할 폴더로 이동 • RESTlet 주요 라이브러리를 Java의 CLASSPATH에 추가 • 소스 저장 폴더에 다음과 같은 두 개의 bat 파일 구성 • jc.bat • j.bat javac -classpath "%CLASSPATH%;D:\0.MY_KUT_DATA\restlet-jse-2.0.15\lib\org.restlet.jar" %1 java -classpath "%CLASSPATH%;D:\0.MY_KUT_DATA\restlet-jse-2.0.15\lib\org.restlet.jar;." %1 LINK@KOREATECH

  21. Restlet Example-1 • HelloWorld 예제 – Server RESTletHelloWorld.java import org.restlet.Server; import org.restlet.data.Protocol; import org.restlet.resource.Get; import org.restlet.resource.ServerResource; public class RESTletHelloWorld extends ServerResource { public static void main(String[] args) throws Exception { // Create the HTTP server and listen on port 8182 new Server(Protocol.HTTP, 8182, RESTletHelloWorld.class).start(); } @Get public String toString() { return “Hello, RESTlet World!"; } } 컴파일: jc RESTletHelloWorld.java 실행: j RESTletHelloWorld LINK@KOREATECH

  22. Restlet Example-1 • HelloWorld 예제 – Client • 방법 1: 브라우저에서 http://localhost:8182/ 접속 • 방법 2 RESTletHelloWorldClient.java import org.restlet.resource.ClientResource; public class RESTletHelloWorldClient extends ClientResource { public static void main(String[] args) throws Exception { // Create the client resource ClientResource resource = new ClientResource("http://localhost:8182/"); // Write the response entity on the console resource.get().write(System.out); } } 컴파일: jc RESTletHelloWorldClient.java 실행: j RESTletHelloWorldClient LINK@KOREATECH

  23. Restlet Example-2 • TextMessage 예제 – Server (1/2) RESTInfoService.java import org.restlet.Application; import org.restlet.Request; import org.restlet.Response; import org.restlet.Restlet; import org.restlet.Server; import org.restlet.data.MediaType; import org.restlet.data.Protocol; public class RESTInfoService extends Application { public static void main(String[] args) throws Exception { // Create the HTTP server and listen on port 8182 Server server = new Server(Protocol.HTTP, 8182); server.setNext(new RESTInfoService()); server.start(); } LINK@KOREATECH

  24. Restlet Example-2 • TextMessage 예제 – Server (2/2) RESTInfoService.java public Restlet restlet = new Restlet() { @Override public void handle(Request request, Response response) { String message = "Method : " + request.getMethod() + '\n' + "Resource URI : " + request.getResourceRef() + '\n' + "IP address : " + request.getClientInfo().getAddress() + '\n' + "Agent name : " + request.getClientInfo().getAgentName() + '\n' + "Agent version : " + request.getClientInfo().getAgentVersion(); response.setEntity(message, MediaType.TEXT_PLAIN); } }; @Override public Restlet createInboundRoot() { return restlet; } } LINK@KOREATECH

  25. Restlet Example-3 • Route 예제 – Server (1/3) RESTRouteService.java import org.restlet.Application; import org.restlet.Request; import org.restlet.Response; import org.restlet.Restlet; import org.restlet.Server; import org.restlet.data.MediaType; import org.restlet.data.Protocol; import org.restlet.routing.Router; public class RESTRouteService extends Application { public static void main(String[] args) throws Exception { // Create the HTTP server and listen on port 8182 Server server = new Server(Protocol.HTTP, 8182); server.setNext(new RESTRouteService()); server.start(); } LINK@KOREATECH

  26. Restlet Example-3 • Route 예제 – Server (2/3) RESTRouteService.java public Restlet restlet1 = new Restlet() { public void handle(Request request, Response response) { String message = "This is a information for students"; response.setEntity(message, MediaType.TEXT_PLAIN); } }; public Restlet restlet2 = new Restlet() { public void handle(Request request, Response response) { String message = "<?xml version='1.0' encoding='UTF-8'?><students> <student><id>1</id><url>/students/1</url></student> <student><id>2</id><url>/students/2</url></student></students>"; response.setEntity(message, MediaType.TEXT_XML); } }; LINK@KOREATECH

  27. Restlet Example-3 • Route 예제 – Server (3/3) RESTRouteService.java public Restlet restlet3 = new Restlet() { public void handle(Request request, Response response) { String message = "<?xml version='1.0' encoding='UTF-8'?><student> <id>1</id><name>Jun-Ha Jung</name><address>Seoul</address> </student>"; response.setEntity(message, MediaType.TEXT_XML); } }; @Override public Restlet createInboundRoot() { Router router = new Router(); router.attach("http://localhost:8182/info", restlet1); router.attach("http://localhost:8182/students", restlet2); router.attach("http://localhost:8182/students/1", restlet3); return router; } } LINK@KOREATECH

  28. Restlet Example-4 • QueryString 예제 – Server (1/2) RestletQueryString.java import org.restlet.Application; import org.restlet.Request; import org.restlet.Response; import org.restlet.Restlet; import org.restlet.Server; import org.restlet.data.MediaType; import org.restlet.data.Form; import org.restlet.data.Protocol; import org.restlet.routing.Router; public class RestletQueryString extends Application { public static void main(String[] args) throws Exception { // Create the HTTP server and listen on port 8182 Server server = new Server(Protocol.HTTP, 8182); server.setNext(new RestletQueryString()); server.start(); } LINK@KOREATECH

  29. Restlet Example-4 • QueryString 예제 – Server (2/2) • 테스트 – 웹 브라우저로 접속 • http://localhost:8182/query?num=10 RestletQueryString.java public Restlet restlet1 = new Restlet() { public void handle(Request request, Response response) { Form queryString = request.getResourceRef().getQueryAsForm(); String num = queryString.getValues("num"); String message = "<?xml version='1.0' encoding='UTF-8'?><num>" + num + "</num>"; response.setEntity(message, MediaType.TEXT_XML); } }; @Override public Restlet createInboundRoot() { Router router = new Router(); router.attach("http://localhost:8182/query", restlet1); return router; } } LINK@KOREATECH

  30. [실습] • REST 기반 계산기 프로그램 (1/3) • 클라이언트에서 호출할 URL 및 이에 대한 XML 응답 • http://localhost:8182/plus?num1=10&num2=9 • http://localhost:8182/substraction?num1=10&num2=9 <?xml version='1.0' encoding='UTF-8'?> <plus> <num1>10</num1> <num2>9</num2> <solution>18</solution> </plus> <?xml version='1.0' encoding='UTF-8'?> <substraction> <num1>10</num1> <num2>9</num2> <solution>1</solution> </substraction> LINK@KOREATECH

  31. [실습] • REST 기반 계산기 프로그램 (2/3) • 클라이언트에서 호출할 URL 및 이에 대한 XML 응답 • http://localhost:8182/product?num1=10&num2=9 • http://localhost:8182/divide?num1=10&num2=9 • http://localhost:8182/divide?num1=10&num2=0 <?xml version='1.0' encoding='UTF-8'?> <product> <num1>10</num1> <num2>9</num2> <solution>90</solution> </product> <?xml version='1.0' encoding='UTF-8'?> <divide> <num1>10</num1> <num2>9</num2> <solution>1.111</solution> </divide> <?xml version='1.0' encoding='UTF-8'?> <divide> <num1>10</num1> <num2>0</num2> <solution>Error!</solution> </divide> LINK@KOREATECH

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