Morena middleware2012

MORENA: A Middleware for Programming NFC-enabled Android Applications as Distributed Object-Oriented Programs

Andoni Lombide CarretonKevin PinteWolfgang De Meuter

ACM/IFIP/USENIX 13th International Conference on Middleware 2012December 5 2012Montreal, Canada

Monday 28 January 13

• NFC (touch range).

• Callback on activities to detect RFID tags with subscribed MIME-type in memory.

• File access abstraction

RFID in Android

NdefMessage: { , , }

NdefRecord byte array

read write


Drawbacks of the Android NFC API

• Manual failure handling (and NFC causes A LOT of failures because of its hardware characteristics).

• Blocking communication (Android documentation recommends to use a separate thread for many RFID operations).

• Manual data conversion

• Tight coupling with activity-based architecture


Lessons Learnt from Previous Ambient-Oriented Programming Research

• Using objects as first class software representations for RFID-tagged “things” is a nice abstraction.

• These objects can be directly stored in the RFID tags’ memory to minimize data conversion.

• Event-driven discovery (fortunately built-in into Android).

• Asynchronous reads and writes.


Application

Middleware Architecture

Android

Tag level

Thing level One middlewarefor Android 4.0

or higher


Evaluation: WiFi Sharing Application




Things

public class WifiConfig extends Thing {

public String ssid_; public String key_;

public WifiConfig(ThingActivity<WifiConfig> activity, String ssid, String key) { super(activity); ssid_ = ssid; key_ = key; } public boolean connect(WifiManager wm) {

// Connect to ssid_ with password key_ };}

From now on, we don’t have to worry about the

activity anymore.

Supported serialization: - JSON-serializable fields. - Skipping transient fields. - Deep serialization, no cycles.


Initializing Things

@Overridepublic void whenDiscovered(EmptyRecord empty) { empty.initialize( myWifiThing, new ThingSavedListener<WifiConfig>() { @Override public void signal(WifiConfig thing) { toast("WiFi joiner created!"); } }, new ThingSaveFailedListener() { @Override public void signal() { toast("Creating WiFi joiner failed, try again."); } });}

As soon as an empty tag is detected


Discovering and Reading Things

@Overridepublic void whenDiscovered(WifiConfig wc) { toast("Joining Wifi network " + wc.ssid_); wc.connect();}

As soon as a WifiConfig tag is detected

Contains cached fields for synchronous access.

Physical reads must be asynchronous.


Saving Modified Things

myWifiConfig.ssid_ = "MyNewWifiName";myWifiConfig.key_ = "MyNewWifiPassword";

myWifiConfig.saveAsync( new ThingSavedListener<WifiConfig>() { @Override public void signal(WifiConfig wc) { toast("WiFi joiner saved!"); } }, new ThingSaveFailedListener() { @Override public void signal() { toast("Saving WiFi joiner failed, try again."); } });


Broadcasting Things to Other Phones

myWifiConfig.broadcast( new ThingBroadcastSuccessListener<WifiConfig>() { @Override public void signal(WifiConfig wc) { toast("WiFi joiner shared!"); } }, new ThingBroadcastFailedListener<WifiConfig>() { @Override public void signal(WifiConfig wc) { toast("Failed to share WiFi joiner, try again."); } });

Will trigger whenDiscovered on the receiving phone with the broadcasted thing




Middleware Architecture

Android

Tag level

Thing level One middlewarefor Android 4.0

or higher

Application


Detecting RFID Tags

new MyTagDiscoverer(this, THING_TYPE, new NdefMessageToStringConverter(), new StringToNdefMessageConverter());

private class MyTagDiscoverer extends TagDiscoverer { @Override public void onTagDetected(TagReference tagReference) { readTagAndUpdateUI(tagReference); } @Override public void onTagRedetected(TagReference tagReference) { readTagAndUpdateUI(tagReference); }}


The Tag Reference Abstraction


Reading RFID Tags

tagReference.read( new TagReadListener() { @Override public void signal(TagReference tagReference) { // tagReference.getCachedData() } }, new TagReadFailedListener() { @Override public void signal(TagReference tagReference) { // Deal with failure } });


Writing RFID Tags

tagReference.write( toWrite, new TagWrittenListener() { @Override public void signal(TagReference tagReference) { // Handle write success } }, new TagWriteFailedListener() { @Override public void signal(TagReference tagReference) { // Deal with failure } });


Fine-grained Filtering

private class MyTagDiscoverer extends TagDiscoverer { @Override public void onTagDetected(TagReference tagReference) { readTagAndUpdateUI(tagReference); } @Override public void onTagRedetected(TagReference tagReference) { readTagAndUpdateUI(tagReference); }

@Override public boolean checkCondition(TagReference tagReference) { // Can be used to apply a predicate // on tagReference.getCachedData() }}


Conclusion

• Event-driven discovery.

• Non-blocking communication:

• Things: cached copy, asynchronous saving of cached data.

• TagReferences: first class references to RFID tags offering asynchronous reads and writes.

• Automatic data conversion

• Looser coupling from activity-based architecture

• Data structures over several tags, stronger consistency guarantees?


MORENA: A Middleware for Programming NFC-enabled Android Applications as Distributed Object-Oriented Programs

Andoni Lombide CarretonKevin PinteWolfgang De Meuter

ACM/IFIP/USENIX 13th International Conference on Middleware 2012December 5 2012Montreal, Canada


Morena middleware2012

Documents