Programming for RESTful-SOA

1. Programming for RESTful-SOA An introduction to building aSOA System with light-weighted RESTful Web Services (Web Services without SOAP or WSDL) Xiong Haoyi xhyccc@vip.sina.com Huazhong University of Science and Technology

2. Review of REST • REST, means REpresentational State Transfer, was firstly raised by Roy Thomas Fielding in his doctoral thesis --“Architectural Styles and the Design of Network-based Software Architectures”（University of California - Irvine，2000） • Rest, broadly used in the web applications, is considered as the basic architecture of web. • The typical technologies based on REST include WebDAV, Resource-Oriented Web System etc.

4. Principles of RESTful Programming • URI-Oriented Designing • Linking Anything! • Using the standard Methods of HTTP • Multi-Representation of Resource • Stateless Communication

5. URI-Oriented Designing • Uniform Resource Identifier--”a compact string of characters used to identify or name a resource on the Internet.” • URI could be the UUID for any Object in this world. • The operations over resource could represent as the operations with the URI.

6. Example of URI and REST Index to distinct Customer’s Detail with customer id:1234 http://example.com/customerdetails/1234 Index to All Orders in the date of 2007 http://example.com/orders/2007/ Example above Powered by Stefan Tilkov

7. HTTP Methods and Service Operations • HTTP Methods including GET, POST, DELETE, PUT and HEAD, in some degree, could map to the CRUD actions which are the typical operations towards to resources. • Service Operations , binding with semanteme of transcation, focus on the package of complex process and business activity.

8. REST vs RPC • REST • Resources—Commands are defined in simple terms: resources to be retrieved, stored / get, set—difficult to do many joins • RPC • Calling—Commands are defined in methods with varying complexity: depending on “standard”—easier to hide complex things behind a method • REST • Nouns—Exchanging resources and concepts • RPC • Verbs—Exchanging methods

9. REST in Action • RestfulBeansServices, as the main result of our research, now is published as an open source software with the apache license on Google Code under the name of “RESTfulCRUDBeans” • It is a Spring based framework deploying the Pojos as RESTful Web Services.

10. REST in Action • Sample Code: • Define a RESTful Web Service with annotation package org.lightechs.restfulbeans.sample; import org.lightechs.restfulbeans.annotation.*; …… @DefaultTransformer(name=“TextureTransformer") /*Index to default Representation Transformer Defined in Spring beans*/ public class SampleRESTfulBean{ …… }

11. REST in Action • Sample Code: • Define a RESTful Web Service Operation with annotation ..... @ReadMethod /*Reading with GET Method*/ @ResourceURI(URI="hello/${id}")/*URI Designing*/ public String getHelloWorld(@PathParam(name="${id}", converter= "Int“ ) int i) { return “Hello!”+i; } … Invoke this operation with URI: GET hello/123 Accept: text /* if the accept fragment is invalid, the server would choose default one*/ Result of Server: Hello!123 (the result depends on the representation of ‘text’)

12. REST in Action • Sample Code:Transformer Interface package org.lightechs.restfulbeans.transformer; import javax.servlet.http.HttpServletResponse; public interface transformer{ public void doTransformer(Object obj,HttpServletResponse response); /*Object means operation result, response means the HTTP response. Implements this method and define the way reflect in to response stream. */ }

13. REST in Action • Sample Transformer,Transform String into stream package org.lightechs.restfulbeans.transformer; import javax.servlet.http.HttpServletResponse; import net.sf.json.*; ….. public void doTransformer(Object obj, HttpServletResponse response) { try{ String str=(String)obj; /*if obj is not instance of String, it will throw cast exception to container*/ response.setContentType(“plain/text; charset=utf-8"); PrintWriter pw=reponse.getWriter(); pw.write(str); Pw.close(); }catch(IOException e){ e.printStack(); } } …..

14. REST in Action • Sample Code: Single String Converter Interface package org.lightechs.restfulbeans.converter; public interface SingleStringConverter extends ConvertInterface{ public Object convert(String str); /*str means the part of URI such as “http://....../Operation/${id}” The part named ${id} would convert int to Object as your wish by implementation of this method. */ }

15. REST in Action • Sample Converter, Covert String into Integer package org.lightechs.restfulbeans.converter; public class Str2Integer implements SingleStringConverter{ public Object convert(String str) { return new Integer(str); /*if this str is not in the format of integer the methods would throws exception to container*/ } }

16. REST in Action • Sample Multi-String Converter, Covert Strings into File package org.lightechs.restfulbeans.converter; import java.io.File; public class MultiStr2FilePath implements MultiStringConverter{ public Object convert(String[] strs) {/*Multi-String convert Method*/ String temp=strs[0]; for(int i=1;i<strs.length;i++){ temp+=(File.pathSeparator+strs[i]); } File file=new File(temp); return file; } } Eg: “http://..../operation/Disk:/Path1/Path2/.../File” could index to native file of server side

17. REST in Action • Annotation of this container • @PathParam : the Parameter in URI Path. • @NamedParam :named parameter in query String. • @HttpRequest :Mutipart fragment of Http Request (eg. file upload) • @ResourceURI :Mapping the URI with PathParams (eg.@ResourceURI(“hello/${id}/.../”)-->@PathParam(name=${id},...) ) • @DefaultTransformer : firm default transformer for the service such as Json, TableList in sample source. • @ReadMethod,@CreateMethod,@UpdateMethod ,@DeleteMethod could mapping the operation into GET,POST,PUT and DELETE Method.

18. Special RESTful Web Services • QBE (Query By Example)! • Asynchronous Message Queue

19. Query By Example • URI-Query Mapping Original URI: GET db/STUDENT/hust/2005/ceee/ ACCEPT:NAME+CODE+AGE+SEX/COLLEGE+YEAR+DEPARTMEN T/X-JSON Mapped SQL: SELECT NAME, CODE, AGE, SEX FROM student WHERE COLLEGE=’hust’ AND YEAR=’2005’ AND DEPARTMENT='ceee’

20. Query By Example

21. Asynchronous Message Queue • Asynchronous Message Queue over keep-alive HTTP Connection • The Server Response Content-type: multipart/mixed; boundary=”StudentMessage” --StudentMessage Content-type: X-JSON {code:”001”, name:”Sam” ,age=20} --StudentMessage Content-type: X-JSON {code:”002”, name:”Lily” ,age=20} --StudentMessage--

22. Introduction to Our Team • Our team—LighTECHs which is a student team of HUST focus on Open-Source Java Web Container. • Main Staffs of LighTECHs Xiong Hao-yi : System analyst, Architecture Leader Bie Rui : Sofware Designer, Chief Programmer He Lingli : Software Designer, Interrupter …….

23. Q&A