Rest dengan restlet

REZA LESMANAUniversitas Gunadarma

Saturday, February 5, 2011

RESTUsing Restlet Framework


RESTRepresentational State Transfer


WHAT IS REST?

GAYA ARSITEKTUR SOFTWARE UNTUK ARSITEKTUR APLIKASI BERBASIS JARINGAN

BASICALLYWEB SERVICES ARCHITECTURE


WHY USE REST?UNIFORM INTERFACE

SEMUA KOMPONEN APLIKASI DALAM WEB SERVICES BERINTERAKSI DENGAN CARA YANG SAMA


UNIFORM INTERFACEone of the feature of REST


UNIFORM INTERFACEResource Identification [1]

RESOURCEinformasi yang dibutuhkan oleh user untuk

menjalankan proses bisnis dari suatu aplikasi



Uniform Resource Identifier (URI)

Contoh : HTTP URL



URI Template

http://contohaja.com/message/{index}


http://contohaja.com/messages/%7B

http://contohaja.com/messages/%7B

RESTLET FRAMEWORKapplication building block


RESTLET FRAMEWORKservlet configuration (web.xml)

 <context-param> <param-name>org.restlet.application</param-name> <param-value> com.helloworld.main.MainApplication </param-value> </context-param>  <servlet> <servlet-name>RestletServlet</servlet-name> <servlet-class> org.restlet.ext.servlet.ServerServlet </servlet-class> </servlet>  <servlet-mapping> <servlet-name>RestletServlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping>


http://web.xml

http://web.xml


aplikasi penyimpanan pesan dalam stack

•Daftar Pesan --->

• Top of Stack --->

• Pesan Tunggal --->

• “/” ---> MessagesResource

• “/message/ ---> MessageResource

• “/message/{index} ---> MessageResource


RESTLET FRAMEWORKMainApplication

public class MainApplication extends Application {

public MainApplication(Context parentContext) { super(parentContext); } @Override public synchronized Restlet createInboundRoot() { Router router = new Router(getContext()); router.attach("/", MessagesResource.class); router.attach("/message/", MessageResource.class); router.attach("/message/{messageIndex}", MessageResource.class); return router; }}


UNIFORM INTERFACEManipulation Through Representation [1]

REPRESENTATION

representasi dari resource


RESTLET FRAMEWORKapplication building block



HTTP METHOD as Popular Practices

• HTTP POST --->

• HTTP GET --->

• HTTP PUT --->

• HTTP DELETE --->

•membuat Resource baru (Create)

•mendapatkan Resource (Read)

•mengubah Resource (Update)

•menghapus Resource (Delete)



Another Protocol?

• Gunakan standar protokol komunikasi sesuai dengan spesifikasinya

• Perhatikan Safety dan Idempotency dari method

• Safety : tidak menghasilkan “efek samping” pada resource

• Idempotency : dilakukan berulang-ulang hasilnya sama



Standardized Document Structure as Representation

• XHTML

• XML

• Atom Pub

•OData

•MPEG

•MP3

• AVI

• Text/Audio/Video Streaming



Not Only HTTP

TEXT/AUDIO/VIDEO STREAMINGContoh : VoIP

Using SIP or XMPP


RESTLET FRAMEWORKMainApplication

public class MainApplication extends Application {

public MainApplication(Context parentContext) { super(parentContext); } @Override public synchronized Restlet createInboundRoot() { Router router = new Router(getContext()); router.attach("/", MessagesResource.class); router.attach("/message/", MessageResource.class); router.attach("/message/{messageIndex}", MessageResource.class); return router; }}


RESTLET FRAMEWORKManipulation Through Representation [1]

public class MessageResource extends ServerResource { @Post public Representation addMessage(Representation entity) { StringRepresentation representation = null; String result = ""; try { result = HelloBusiness.create(entity.getText()); } catch (IOException e) { setStatus(Status.SERVER_ERROR_INTERNAL ); } representation = new StringRepresentation (result, MediaType.APPLICATION_XML); return representation; }



@Get("xml") public Representation get(){ String index = (String)getRequest().getAttributes().get("messageIndex"); StringRepresentation representation = null; String result = ""; try{ if(index != "" && index != null){ result = HelloBusiness.get(Integer.parseInt(index)); }else{ result = HelloBusiness.get(); } representation = new StringRepresentation (result, MediaType.APPLICATION_XML); return representation; }catch(Exception e){ setStatus(Status.CLIENT_ERROR_NOT_FOUND); representation = new StringRepresentation ("no item found", MediaType.TEXT_PLAIN); return representation; } }



@Put public Representation put(Representation entity){ StringRepresentation representation = null; String result = ""; try { result = HelloBusiness.update(entity.getText()); } catch (IOException e) { setStatus(Status.SERVER_ERROR_INTERNAL ); } representation = new StringRepresentation (result, MediaType.APPLICATION_XML); return representation; }



@Delete public Representation delete(){ StringRepresentation representation = null; String result = ""; try { result = HelloBusiness.delete(); }catch(NoMoreItemException ne){ setStatus(Status.CLIENT_ERROR_FORBIDDEN); representation = new StringRepresentation ("Tidak boleh, udah kosong", MediaType.TEXT_PLAIN); return representation; } representation = new StringRepresentation (result, MediaType.APPLICATION_XML); return representation; }


UNIFORM INTERFACESelf-Descriptive Messages [1]

TWO FACTORS

The Protocol MessageThe Media Type (Type of Representation)



The Protocol Message

•HTTP Header --> Content Negotiation

• Contoh : Accept : application/xml

•Status Respon :

• Contoh : HTTP 1.1 / 200 OK ,HTTP 1.1 / 403 FORBIDDEN



The Media Type

•Struktur Dokumen Bisa Mudah Diolah

•Contoh :

•XML (application/xml)

•Atom Pub (application/atom+xml)


Contoh MediaType XML

<messages><message>

<messageid>120</messageid><author>Reza</author><created>2011/02/04 08:20:12</created><value>Hello, World!</value><link>/message/120</link>

<message>................

<messages>


<entry> <id>urn:uuid:95506d98-aae9-4d34-a8f4-1ff30bece80c</id> <title type=ʹ′ʹ′textʹ′ʹ′>product created</title> <updated>2009-07-05T10:25:00Z</updated> <link rel=ʹ′ʹ′selfʹ′ʹ′ href=ʹ′ʹ′http://starbucks.com/products/notifications/95506d98-aae9-4d34-a8f4-1ff30bece80cʹ′ʹ′/><link rel=ʹ′ʹ′relatedʹ′ʹ′ href=ʹ′ʹ′http://starbucks.com/products/527ʹ′ʹ′/> <category scheme=ʹ′ʹ′http://starbucks.com/products/categories/typeʹ′ʹ′ term=ʹ′ʹ′productʹ′ʹ′/> <category scheme=ʹ′ʹ′http://starbucks.com/products/categories/statusʹ′ʹ′ term=ʹ′ʹ′newʹ′ʹ′/> <content type=ʹ′ʹ′application/vnd.starbucks+xmlʹ′ʹ′>

<product xmlns=ʹ′ʹ′http://schemas.starbucks.com/productʹ′ʹ′ href=ʹ′ʹ′http://starbucks.com/products/527ʹ′ʹ′>

<name>Fairtrade Roma Coffee Beans</name> <size>1kg</size><price>10</price> <currency>$</currency></product>

</content></entry>

Contoh MediaType Atom


http://restbucks.com/products/notifications/95506d98-aae9-4d34-a8f4-




http://restbucks.com/products/527


http://restbucks.com/products/categories/type

http://restbucks.com/products/categories/type

http://restbucks.com/products/categories/status

http://restbucks.com/products/categories/status

http://schemas.restbucks.com/product

http://schemas.restbucks.com/product



RESTLET FRAMEWORKSelf-Descriptive Message [1]

@Get("xml") public Representation get(){ String index = (String)getRequest().getAttributes().get("messageIndex"); StringRepresentation representation = null; String result = ""; try{ if(index != "" && index != null){ result = HelloBusiness.get(Integer.parseInt(index)); }else{ result = HelloBusiness.get(); } representation = new StringRepresentation (result, MediaType.APPLICATION_XML); return representation; }catch(NotFoundException e){ setStatus(Status.CLIENT_ERROR_NOT_FOUND); representation = new StringRepresentation ("no item found", MediaType.TEXT_PLAIN); return representation; } }


RESTLET FRAMEWORKSelf-Descriptive Message [2]

<messages><request>GET : ALL</request><message> <request>GET</request> <value>Hello, World!</value> <link>/message/0</link></message><message> <request>GET</request> <value>Halo, Dunia!</value> <link>/message/1</link></message><message> <request>GET</request> <value>Apa Kabar?</value> <link>/message/2</link></message></messages>



UNIFORM INTERFACEHypermedia as The Engine of Application

State (HATEOAS) [1]

orHypermedia constraints


UNIFORM INTERFACEHypermedia Constraint [1]

• Inti dari Representational State Transfer

•Menyatukan informasi proses bisnis dalam representasi resource



explains why named as “representational state transfer”



execution of business process

“Consumers in a hypermedia system cause state transitions by visiting and manipulating resource state. Interestingly, the application state changes that result from a consumer driving a hypermedia system resemble the execution of a business process. This suggests that our services can advertise workflows using hypermedia.” - Jim Webber - REST In Practice



Best Practices

•Menambahkan informasi possible next states langsung di dalam Representation

•Caranya (untuk saat ini) :

•possible next states ----> hyperlinks



examples<entry><order xmlns=ʹ′ʹ′http://schemas.starbucks.comʹ′ʹ′> <location>takeAway</location> <item>

<name>latte</name> <quantity>1</quantity> <milk>whole</milk> <size>small</size>

</item> <cost>2.0</cost> <status>payment-expected</status><link rel=ʹ′ʹ′http://relations.restbucks.com/paymentʹ′ʹ′

href=ʹ′ʹ′https://restbucks.com/payment/1234ʹ′ʹ′/> <link rel=ʹ′ʹ′http://relations.restbucks.com/special-offerʹ′ʹ′

href=ʹ′ʹ′http://restbucks.com/offers/cookie/1234ʹ′ʹ′/></entry>


http://schemas.restbucks.com

http://schemas.restbucks.com

http://relations.restbucks.com/payment

http://relations.restbucks.com/payment

https://restbucks.com/payment/1234

https://restbucks.com/payment/1234

http://relations.restbucks.com/special-offer

http://relations.restbucks.com/special-offer

http://restbucks.com/offers/cookie/1234

http://restbucks.com/offers/cookie/1234


hypermedia support in MediaType

•Lebih baik jangan gunakan MediaType XML untuk menambahkan hyperlinks di dalamnya.

• Tidak ada dukungan langsung (native link tag) untuk hyperlinks

•Gunakan Hypermedia Types (-Mike Amundsen)

•Contoh : Atom

•http://amundsen.com/hypermedia/Saturday, February 5, 2011

http://amundsen.com/hypermedia/

http://amundsen.com/hypermedia/

RESTLET FRAMEWORKHypermedia Constraints [1]

•Native support untuk mempermudah manajemen hypermedia constraints terdapat pada Restlet versi 2.1 (dalam pengembangan)

•Solusi : Tambahkan secara manual ! :D

•Solusi : Pakai versi 2.1 dengan resiko sendiri


CONTOH APLIKASI LAINSOCIAL COMMERCE [1]

• Indeks Aplikasi Memuat :

•Daftar Toko Online (dengan link masing-masing)

• Link ke User Profile

• Link ke Pengaturan Toko Online milik user



•Masuk ke salah satu Toko Online (melalui link). Memuat :

• Profil singkat penjual (dengan link ke profil lengkap)

•Daftar Deskripsi Singkat Produk (dengan link masing-masing untuk deskripsi lengkap)

• Link ke Indeks



• Lihat deskripsi lengkap produk (melalui link). Memuat :

• Informasi produk

• Link untuk memesan

• Link kembali ke Toko Online










THANK YOU !

QUESTION?

Technology

Rest dengan restlet