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Octavia Powers
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Andrid prgramming curse Sessin bjectives

1 Andrid prgramming curse Sessin bjectives Intrductin URL & HttpCnnectin Netwrking APIs Using URL t read data Using HttpCnnectin pst data Reading netwrk state Web Service SOAP REST By Võ Văn Hải Faculty f Infrmatin Technlgies 2 1

Intrductin Within an Andrid applicatin yu shuld avid perfrming lng running peratins n the user interface thread. This includes file and netwrk access. As f Andrid 3.

-- fr internet access --> <uses-permissin andrid:name="andrid.permissin.internet" /> <!-- fr netwrk states --> <uses-permissin andrid:name="andrid.permissin.access_network_state" /> <!

2 Intrductin Within an Andrid applicatin yu shuld avid perfrming lng running peratins n the user interface thread. This includes file and netwrk access. As f Andrid 3.0 (Hneycmb) the system is cnfigured t crash with a NetwrkOnMainThreadExceptin exceptin, if netwrk is accessed in the user interface thread. Yu may als need these permissin  <uses-permissin andrid:name="andrid.permissin.internet" />  <uses-permissin andrid:name="andrid.permissin.access_network_state" />  <uses-permissin andrid:name="andrid.permissin.write_settings" /> 3 Check the netwrk availability Befre cnnect t netwrk, yu shuld check the state f cnnectin 4 2

3 Accessing netwrk thrugh a prxy If yu want t test with the Andrid simulatr using a prxy. Yu can set the prxy via the Settings class. <uses-permissin andrid:name="andrid.permissin.write_settings" /> Perfrm Netwrk Operatins n a Separate Thread Netwrk peratins can invlve unpredictable delays. T prevent this frm causing a pr user experience, always perfrm netwrk peratins n a separate thread frm the UI AsyncTask r ther Asynchrnus Techniques 3

URL URL & HttpCnnectin A URL, shrt fr "Unifrm Resurce Lcatr", is a way t

The resurce can be an HTML page, an image r simply any file.

cm/ Name f the prtcl, which is used t fetch the resurce frm the Internet.

4 URL URL & HttpCnnectin A URL, shrt fr "Unifrm Resurce Lcatr", is a way t unambiguusly identify the lcatin f a resurce n the Internet. The resurce can be an HTML page, an image r simply any file. URL frm prtcl://resurce Prtcl Identifier Name f the prtcl, which is used t fetch the resurce frm the Internet. Resurce Name Address f the resurce Separated frm the prtcl identifier with a cln and tw frward slashes Resurce frmat depends n the prtcl being used

5 Reading Data frm a URL The penstream() methd cnnects t the server specified in the URL and returns an InputStream bject fed by the data frm that cnnectin. public final InputStream penstream() thrws IOExceptin Any headers that precede the actual data are stripped ff befre the stream is pened. Netwrk cnnectins are less reliable and slwer than files. Buffer with a BufferedReader r a BufferedInputStream. Using Asynchrnus techniques

URLCnnectins The java.net.urlcnnectin class is an abstract class that handles cmmunicatin with different kinds f servers like ftp servers and web servers.

6 URLCnnectins The java.net.urlcnnectin class is an abstract class that handles cmmunicatin with different kinds f servers like ftp servers and web servers. Prtcl specific subclasses f URLCnnectin handle different kinds f servers. By default, cnnectins t HTTP URLs use the GET methd. Capacities: Can send utput as well as read input Can pst data Can read headers frm a cnnectin I/O Acrss a URLCnnectin Data may be read frm the cnnectin in ne f tw ways raw by using the input stream returned by getinputstream() thrugh a cntent handler with getcntent(). Data can be sent t the server using the utput stream prvided by getoutputstream()

7 Send request t server Since a URLCnnectin desn't allw utput by default, yu have t call setdoutput(true) befre asking fr an utput stream. Get respnse frm server

Determining and Mnitring the Cnnectivity Status Sme f the mst cmmn uses fr repeating alarms and backgrund services is t schedule regular updates f applicatin data frm Internet resurces, cache data, r

8 Determining and Mnitring the Cnnectivity Status Sme f the mst cmmn uses fr repeating alarms and backgrund services is t schedule regular updates f applicatin data frm Internet resurces, cache data, r execute lng running dwnlads. But if yu aren't cnnected t the Internet, r the cnnectin is t slw t cmplete yur dwnlad, why bth waking the device t schedule the update at all? Yu can use the CnnectivityManager t check that yu're actually cnnected t the Internet, and if s, what type f cnnectin is in place. Determine if Yu Have an Internet Cnnectin There's n need t schedule an update based n an Internet resurce if yu aren't cnnected t the Internet. The fllwing snippet shws hw t use the CnnectivityManager t query the active netwrk and determine if it has Internet cnnectivity

9 Determine the Type f yur Internet Cnnectin It's als pssible t determine the type f Internet cnnectin currently available. Device cnnectivity can be prvided by Mbile data, WiMAX, Wi-Fi, and ethernet cnnectins. Mbile data csts tend t be significantly higher than Wi-Fi, s in mst cases, yur app's update rate shuld be lwer when n mbile cnnectins. Having disabled yur updates, it's imprtant that yu listen fr changes in cnnectivity in rder t resume them nce an Internet cnnectin has been established. Mnitr fr Changes in Cnnectivity The CnnectivityManager bradcasts the andrid.net.cnn.connectivity_change actin whenever the cnnectivity details have changed. Yu can register a bradcast receiver in yur manifest t listen fr these changes and resume (r suspend) yur backgrund updates accrdingly. 17 Changes t a device's cnnectivity can be very frequent this bradcast is triggered every time yu mve between mbile data and Wi-Fi. 18 9

Retrieving Andrid Netwrk Status Web Sckets Web Sckets are a standard based n HTTP fr asynchrnus message-based cmmunicatin between a client and a server.

cm/ request, the client and the server can send each ther messages.

10 Retrieving Andrid Netwrk Status Web Sckets Web Sckets are a standard based n HTTP fr asynchrnus message-based cmmunicatin between a client and a server. T start a web scket cmmunicatin, yu create a HTTP GET request with a special HTTP headers. If the server accepts this request, the client and the server can send each ther messages. Messages can be text r binary data and shuld be relatively small, as the web scket prtcl is intended t be used with small paylads in the data. It is gd practice t use JSON as data frmat fr the messages. Yu find a Java library fr bth the server and the client under

11 SOAP Web Service intr Web Service Ref: Curse Sftware Architecture A web service is, therefre, any service that Is available ver the Internet r private (intranet) netwrks Uses a standardized XML messaging system Is nt tied t any ne perating system r prgramming language Is self-describing via a cmmn XML grammar Is discverable via a simple find mechanism Cmpnents f Web Services SOAP (Simple Object Access Prtcl) UDDI (Universal Descriptin, Discvery and Integratin) WSDL (Web Services Descriptin Language)

12 Hw Des a Web Service Wrk? A web service enables cmmunicatin amng varius applicatins by using pen standards such as HTML, XML, WSDL, and SOAP. A web service takes the help f: XML t tag the data SOAP t transfer a message WSDL t describe the availability f service. Create simple SOAP WS

13 URL: methd name params Cnsuming Web Services with ksoap The ksoap library is an elegant, lightweight, and efficient SOAP client library. Dwnlad at: Add reference t prject:

REST intr "REST " was cined by Ry Fielding in his Ph.D. dissertatin t describe a design pattern fr implementing netwrked systems. REST stands fr Representatinal State Transfer.

14 REST intr "REST " was cined by Ry Fielding in his Ph.D. dissertatin t describe a design pattern fr implementing netwrked systems. REST stands fr Representatinal State Transfer. REST is an architecture style fr designing web services All f the majr webservices n the Internet nw use REST Twitter, Yah s web services use REST ebay and Amazn have web services fr bth REST and SOAP Sharepint 2013 intrduces new REST endpints fr almst every API in client bject mdel

15 Http HTTP is an applicatin-level prtcl HTTP has peratins fr transferring representatins between clients and servers. In HTTP GET, POST, PUT, and DELETE are peratins n resurces. Prper use f HTTP eliminates the need fr invent peratins like createorder, getstatus... SOAP uses HTTP as a prtcl t transprt messages but pr use f HTTP peratins. REST - Basics Unlike SOAP and XML-RPC, REST des nt really require a new message frmat The HTTP API is CRUD (Create, Retrieve, Update, and Delete) GET = "give me sme inf" (Retrieve) POST = "here's sme update inf" (Update) PUT = "here's sme new inf" (Create) DELETE = "delete sme inf" (Delete)

16 REST Fundamentals Resurce based architecture. A resurce is accessed via a cmmn interface based n the HTTP standard methds. Identify each resurce using a URL. Every resurce shuld supprt the HTTP cmmn peratins. REST allws that resurces t have different representatins, e.g. text, xml, jsn etc. The rest client can ask fr specific representatin via the HTTP prtcl (Cntent Negtiatin). REST vs. SOAP REST Transprt must be HTTP r HTTPS SOAP Nrmally HTTP/HTTPS but can be smething else Respnse data transmitted as any frmat Transmitted as XML 31 Request is transmitted as URI Lightweight and URI indicate the intend Transmitted as XML T understand the intent must analyse message bdy Easy t call frm JavaScript Easy t build Need JS parsing fr XML Develpment tls are available 32 16

17 JSON vs. XML JSON N validatin scheme XML XSD Fast parsing just as Eval Required xml dc parsing In JavaScript we can wrk as bjects In JavaScript we wrk as strings Sample REST cde

18 Cnsuming REST in Andrid Summary

Network programming 14/01/2013. Introduction. Session objectives. Client/Server working model. Advanced Java Programming Course

Network programming 14/01/2013. Introduction. Session objectives. Client/Server working model. Advanced Java Programming Course Advanced Java Prgramming Curse Netwrk prgramming Sessin bjectives Netwrking intrductin URL Class InetAddress Class By Võ Văn Hải Faculty f Infrmatin Technlgies Industrial University f H Chi Minh City Wrking