The document discusses connecting Android applications to web services using HTTP, XML, JSON, and OAuth. It covers using the HttpClient API to make HTTP requests, parsing responses in XML and JSON formats, and obtaining access tokens from services using OAuth authentication. The document also recommends libraries for tasks like XML/JSON processing and provides examples of client libraries that connect to specific web services.

1. Connecting to Web Services
Sean Sullivan
Android Dev Camp Amsterdam
8 January 2009

3. +

6. • HTTP
• XML
• JSON
• OAuth

7. HTTP request
XML response

8. http://code.google.com/p/jfireeagle

9. jfireeagle uses:
• HttpClient API
• XStream
• OAuth Java library

10. “An open protocol to allow secure API
authorization in a simple and standard method
from desktop and web applications”

11. • use OAuth to access protected data
• your application needs to obtain an access
token from the service provider
• service provider will issue access token
after the user grants permission

12. +
http://code.google.com/p/oauth

13. +
jfireeagle
http://code.google.com/p/jfireeagle/wiki/Android
jpoco
http://code.google.com/p/jpoco/wiki/Android

14. + HTTP
Option 1
• java.net.URL
• java.net.HttpURLConnection
Option 2
• HttpClient 4.0 API

15. HttpClient 4.0 API
• org.apache.http.client.HttpClient
• org.apache.http.impl.client.DefaultHttpClient

16. HttpClient 4.0 API
• org.apache.http.client.methods.HttpGet
• org.apache.http.client.methods.HttpPost
• org.apache.http.client.methods.HttpPut
• org.apache.http.client.methods.HttpDelete

17. HttpClient 4.0 API
• org.apache.http.HttpResponse
• org.apache.http.StatusLine
• org.apache.http.HttpEntity
• org.apache.http.utils.EntityUtils

18. HttpClient programming
• HTTP response status code
• I/O exceptions
• timeouts
• gzip?

19. HttpClient programming
synchronous invocation
public HttpResponse execute(HttpUriRequest request)
asynchronous invocation
public HttpResponse execute(HttpUriRequest request,
ResponseHandler handler)

20. Android UI thread
• user clicks on button
• onClick listener
• Don’t block the UI thread!
• Tip: use java.lang.Runnable

21. Response formats
• XML
• JSON
• RSS, Atom
• other

22. XML processing
• org.w3c.dom package (DOM)
• org.xml.sax package (SAX)
• org.xmlpull package (XPP3)
• XStream
• JDOM
• Apache XmlBeans *
* does not work on Android 1.0

23. JSON processing
• org.json package
• Google GSON library *
• XStream + Jettison
*
• json-lib
*
* does not work on Android 1.0

24. Client libraries
• code.google.com/p/jfireeagle
• code.google.com/p/jpoco
• code.google.com/p/meetup-java-client
• code.google.com/p/upcoming-java-client
• code.google.com/p/gdata-java-client
• flickrj.sourceforge.net

25. Conclusion
• HttpClient API
• use XStream for XML processing
• use org.json package for JSON processing
• OAuth has a learning curve
• OAuth affects user experience

26. Thank you

27. Resources
• http://code.google.com/android/documentation.html
• http://hc.apache.org/httpcomponents-client
• http://code.google.com/p/oauth
• http://xstream.codehaus.org