org.apache.shindig.gadgets
Class AbstractSpecFactory<T>

java.lang.Object
  org.apache.shindig.gadgets.AbstractSpecFactory<T>

Direct Known Subclasses:

DefaultGadgetSpecFactory, DefaultMessageBundleFactory

public abstract class AbstractSpecFactory<T>
extends Object

Basis for implementing GadgetSpec and MessageBundle factories. Automatically updates objects as needed asynchronously to provide optimal throughput.

Nested Class Summary

protected static class	AbstractSpecFactory.Query Holds information used to fetch a spec.
protected static class	AbstractSpecFactory.SpecRetrievalFailedException

Constructor Summary

AbstractSpecFactory(Class<T> clazz, ExecutorService executor, RequestPipeline pipeline, Cache<Uri,Object> cache, long refresh)

Method Summary

protected T	fetchFromNetwork(AbstractSpecFactory.Query query) Retrieves a spec from the network, parses, and adds it to the cache.
protected T	getSpec(AbstractSpecFactory.Query query) Attempt to fetch a spec, either from cache or from the network.
protected abstract T	parse(String content, AbstractSpecFactory.Query query) Parse and return a new spec object from the network.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractSpecFactory

public AbstractSpecFactory(Class<T> clazz,
                           ExecutorService executor,
                           RequestPipeline pipeline,
                           Cache<Uri,Object> cache,
                           long refresh)

Parameters:

clazz - the class for spec objects.

executor - for asynchronously updating specs

pipeline - the request pipeline for fetching new specs

cache - a cache for parsed spec objects

refresh - the frequency at which to update specs, independent of cache expiration policy

Method Detail

getSpec

protected T getSpec(AbstractSpecFactory.Query query)
             throws GadgetException

Attempt to fetch a spec, either from cache or from the network. Note that the query passed here will always be passed, unmodified, to parse(String, Query). This can be used to carry additional context information during parsing.

Throws:

GadgetException

fetchFromNetwork

protected T fetchFromNetwork(AbstractSpecFactory.Query query)
                      throws AbstractSpecFactory.SpecRetrievalFailedException,
                             GadgetException

Retrieves a spec from the network, parses, and adds it to the cache.

Throws:

AbstractSpecFactory.SpecRetrievalFailedException

GadgetException

parse

protected abstract T parse(String content,
                           AbstractSpecFactory.Query query)
                    throws XmlException,
                           GadgetException

Parse and return a new spec object from the network.

Parameters:

content - the content located at specUri

query - same as was passed getSpec(Query)

Throws:

XmlException

GadgetException