Let's Talk:
Efficient Communication
between PHP and Android

Matthew Turland

There (Will) Be Slides

Publications section of http://matthewturland.com

I Work Here

• Internet solutions for ISPs, media companies, and advertisers
• Offices in Buffalo, New York City, and Atlanta
• Clientele includes most of the top 20 USA cable providers
• Great company to work for - join us!

I Co/Wrote These

http://phparch.com

http://sitepoint.com

Also Relevant

Lay of the Land

• Mobile: where it's at
• Service-oriented architecture: ahead of its time
• Increased mobile device availability = increased network strain
• Pinch bandwidth like we did memory in the Old Days (tm)

Lafayette Traffic

Free and Open Source (BSD License)

Related blog post

Objectives

• Build a PHP-based REST web service
• Build an Android (2.3+) client to consume that service
• Explore approaches to efficient communication between the two
  • data serialization
  • data compression

Presumptions

• You have a basic working knowledge of PHP
  • If not, check out PHP and MySQL Development first
• You have a basic working knowledge of Android
  • If not, check out my introductory presentation

HTTP

• RFC 2616 defines the Hypertext Transfer Protocol or HTTP
• Some related references:
  • HTTP Pocket Reference by Clinton Wong, O'Reilly Media
  • HTTP Developer's Handbook by Chris Shiflett, Sam's Publishing
  • php|architect's Guide to Web Scraping with PHP by Matthew Turland, php|architect Press

REST

• Dr. Roy Fielding's doctorol dissertation defines the principles behind Representational State Transfer or REST
• The rest-discuss Yahoo! Group is a great place to talk about it
• Hypermedia is beyond the scope of this presentation — check out Luke Stokes' presentation on it

A Common Request

GET /foo HTTP/1.1
Accept: application/json;q=1, application/xml;q=0.5
Accept-Encoding: gzip, deflate

A Common Response

HTTP/1.1 200 OK
Content-Type: application/json
Content-Encoding: gzip
...

Client Needs Internet Access

More on Permissions

Checking Network State

Client Needs an HTTP Client

• Facilitates communication with REST services
• HttpURLConnection is available in all Android versions
  • However, it has nasty bugs in Eclair and Froyo (2.0.x-2.2.x)
  • For how to handle these, see this article and this code

A Simple Request

Keeping It Asynchronous

• If you block the main (UI) thread, you're going to have a bad time
• Wrap your request logic in an AsyncTask (example) or a service

Accessing Local Services

• If the machine hosting your service is accessible to your Android application by...
  • ... your app running in an emulator on that machine, access the service on IP 10.0.2.2
  • ... your app running on a device plugged into that machine via USB, access the service on IP 10.0.1.2
• Otherwise, your Android application can generally access any machine the host can access using the same hostname

Environment Detection

• Slightly unreliable way: analyze the values of the PRODUCT, MODEL, and FINGERPRINT constants from android.os.Build
• More reliable way: use <meta-data> elements in your manifest file to explicitly set the environment for the build

Server Supported Types

Client Supported Types

Deriving Best Type

Content Negotiation

• What we just did to figure out what type to return
• Detailed in RFC 2616 Section 12
• Also works for encoding, character set, and language

Content Compression

• Common compression schemes:
  • bzip2
  • gzip
  • deflate
• Related: RFC 2616 Section 3.5

Server Compression Schemes

Client Compression Schemes

Deriving Best
Compression Scheme

A Simple Comparison

By the Numbers

• PHP 5.4.12 with Xdebug 2.2.1 for profiling
• Intel C2D 1.83GHz, 4 GB RAM
• YMMV — experiment with types and compression schemes
• TL;DR: if you can, use bzip2

Back to the Client

Decoding the Response

Batteries Not Included

• bzip2 is not natively supported
• Apache Commons Compress library is an easy way to add it
• Two ways to handle this:
  1. Bundle the library JAR
  2. Extract only needed files from the JAR

Stream to String

Parsing the Response

Stream Parsing

Response Caching

• Related headers detailed in subsections of RFC 2616 Section 14
• Server returns a 304 status if the response has not changed
• Two methods
  • Modification time
  • ETag
• If your minimum Android version is Ice Cream Sandwich or higher (>= 4.0/API level 14), use HttpResponseCache

Time-Based Caching

Tag-Based Caching

Pre-ICS Cache Reading

Pre-ICS Cache Writing

That's All, Folks

• Questions? Comments? Discussion?
• E-mail: me@matthewturland.com
• Web site: http://matthewturland.com
• Twitter: @elazar
• Thanks for attending!