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

+

• HTTP
• XML
• JSON
• OAuth

HTTP request
XML response

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

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

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

• 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Thank you

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