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» FasterDDR

welcome

Welcome to the FasterDDR open source project. The project provides read/write and refactor/caching interfaces to WURFL and OpenDDR (experimental) XML files and is written in Java.

overview

The most important features of this project are

• * Lightweight
• * Easy to use - few and simple interfaces
• * Efficient - fast setup and usage

FasterDDR is helpful for CPU- and memory-constrained environments which need access to the WURFL capabilities.

reading

Reading capabilities is straightforward:

// create device repository factory
DDRFactory ddrFactory = new WurflFactory();

// create repository instance
DDR ddr = ddrFactory.newInstance(new File("wurfl.xml"), "UTF-8");

// add patch file
ddrFactory.parsePatch(ddr, new File("wurfl_patch.xml"), "UTF-8");

// get a device using its id
Device device = ddr.getCapabilityDevice("nokia_n95_ver1");

// get the bandwidth as a string
String bandwidthString = device.getStringCapability("max_data_rate");

Alternatively, use one of the convenience methods:

// get the bandwidth as a long with a default value fallback
long bandwidth = device.getLongCapability("max_data_rate", -1L);

Note that zero-length strings ("") returns as null.

writing

Slashing the capabilities you do not need can save a lot of memory, given the DOM-nature of most DDR-APIs.

// get the device description repository and output stream
DDR ddr = getDDR();
OutputStream = getOutputStream();

// get serializer
WurflSerializer serializer = new WurflSerializer();

// add group
serializer.addGroup("object_download");

// add capability to group
serializer.addCapability("object_download", "video_mov");

// add another group
serializer.addGroup("display");

// add capability to group
serializer.addCapability("display", "max_image_width");

// serialize
serializer.serialize(ddr, out);

In addition, it is also possible to add a device filter to remove devices you do not need.

refactoring

Refactoring device description repository files can potentially reduce the size of the output XML file further.

// get the device description repository
DDR ddr = getDDR();

// create a set of the desired output capabilities
Set capabilities = new HashSet();
capabilities.add("streaming_mp4");
capabilities.add("streaming_mov");
capabilities.add("streaming_3g2");
capabilities.add("streaming_3gpp");
		
// create a capability filter
CapabilityFilter capabilityFilter = new CapabilityFilterImpl(capabilities);
		
// create refactorer				
DDRRefactorer refactorer = new WurflRefactorer();

// refactor		
DDR refactoredDDR = refactorer.refactor(ddr, capabilityFilter);

Refactoring reorganizes the device hierarchy, but keeps everything else intact, like device id, user-agent and capability values.
Refactoring should be performed offline, and patches must be incorporated first. Again, a device filter can also used.

example results
Refactoring the capabilities found within each WURFL group, the following reductions were made:

Note that: Results will vary depending on which capabilities you include - as with all optimizations, care should be taken in
verification of the actual improvement.

caching

The project also includes a simple cache filter which helps in populating a delegate cache provided by you. It organizes
devices which do not specify their own capabilities in sets with their parent(s). As one device is assigned a value,
all members in the same set are assigned that value too.

// get the device description repository
DDR ddr = getDDR();

// get your usual cache from somewhere, for your custom value V
CacheProvider<String, V> cacheDelegate = getCache();

// create the cache factory
DDREmptyDescendantCacheFactory factory = new DDREmptyDescendantCacheFactory(ddr);

// get a cache instance
EmptyDescendantCache<V> cache = factory.newEmptyDescendantCache(cacheDelegate);

// as a request is processed, check cache for some device id
V value = cache.get("nokia_n95_ver1");

if(value == null) { // no value is cached
   // generate a new value
   value = createValue("nokia_n95_ver1");
   
   // add value to cache
   cache.put("nokia_n95_ver1", value); // populates all devices in the same groups as nokia_n95_ver1
}

// .. use value in request response

In other words

cache.put("nokia_n95_ver1", value);

can later yield a positive result for

V value = cache.get("nokia_n93_ver1");

if the two devices are in the same set. Use a cache delegate wrapper if you want to use a more structured or complicated
key in your actual backend cache, i.e. for example go from 'nokia_n95_ver1' to '/items/54/nokia_n95_ver1'.

The cache is light-weight and suitable as part of for example EAR or WAR deployment initializations.
There is also a version of this cache for use with the latest WURFL API.

combining cache and refactoring - example results
Refactoring typically increases the number of empty devices, thus adding to the cache effectiveness.
The following tables shows cache statistics before and after refactoring, again for each WURFL group:

Again note that: Results will vary depending on which capabilities you include.
The most important number in the above table is the estimated number of (random, uniformly distributed) requests for (6686 root) devices
required to fill 90% of the cache, before and after refactoring. Refactoring makes the number of empty (root) devices
increase and thus the number of sets go down correspondingly. Then the cache is likely to be populated with fewer requests,
increasing hit rates and so increasing performance.

other features

We managed to squeeze in a few extra essential features:

• * Read access thread safety
• * Compressed device states
• * Optional String internating

See the javadoc for additional documentation.

license

The FasterDDR library is released under the MIT license.

feedback

Please tell us what you think! Use the forums or mailing lists. All feedback is valuable.

weblog

• » 19-Jan-12, 23:59 - FasterDDR 1.2 release - posted by skjolber
• » 25-May-11, 23:59 - FasterDDR 1.1.1 maintenance release - posted by skjolber
• » 26-Apr-11, 23:59 - FasterDDR 1.1 release - posted by skjolber
• » 9-Apr-09, 18:37 - FasterDDR 1.0.1 maintenance release - posted by skjolber
• » 10-Mar-09, 01:36 - FasterDDR 1.0 released - posted by skjolber
• » 7-Mar-09, 21:05 - Sourceforge project approved - posted by skjolber