REST.md

#Connectivity and REST

• Many times we want to use our Android app as a client, in a client-server relationship
• Android supports normal socket programming, through Java's standard libraries
• Most client-server now is done through HTTP and some kind of web services
• Android includes two http clients, Apache's HttpClient and HttpUrlConnection

XML, SOAP etc

• XML solves the syntax problem when communicating
• We defined web services with SOAP, which gives us either RPC or message based services
• SOAP is now considered heavy, disciplined and 'enterprisey'
• performance may be a problem

REST and JSON

• Roy Fielding (one of the creators of the apache web server) proposed the REST model in his PhD dissertation

  • URLs represent objects or resources
  • idea, implemented many ways; not a formal standard
  • use all HTTP methods
    • GET is for reading
    • POST is for creating
    • PUT is for replacing (updating)
    • DELETE is for deleting

• communication is usually done in Json, not XML

  • JSON stands for JavaScript Object Notation
  • Basically the notation for values in javascript, similar to other languages
  • Objects in JSON are defined with a list of name : value pairs, separated by commas, inside {}
  • { age: 3, name:"Orlando"}
  • strings can be single or double quoted; field names can be quoted (need to be quoted if containing spaces etc)

Http Connections in Android

• Apache's HttpClient
• HttpUrlConnection
• We need to add internet permission

    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

• your machine is 10.0.2.2 from the emulator

Json in Java

• JSONObject