SCA Java binding.rss (TUSCANY) created by Dan Becker
http://cwiki.apache.org/confluence/display/TUSCANY/SCA+Java+binding.rss
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h3. <binding.rss> Introduction
The Tuscany Java SCA runtime supports Really Simple Syndication (RSS) using the
<binding.rss> extension. Tuscany can communicate with services that provide or
consume items described in the RSS 1.0 or 2.0 syndication format. The RSS
protcol is an additional conceptual layer that operates on top of the Hyper
Text Transfer Protocol, so it is useful to understand that underlying protocol
as well. Reference materials on these specifications is available here.
* [Hyper Text Transfer Protocol|http://tools.ietf.org/html/rfc2616].
* [RSS 1.0 Specification|http://web.resource.org/rss/1.0/].
* [RSS 2.0 Specification|http://cyber.law.harvard.edu/rss/rss.html].
(on) Some of the function described here is included in the Tuscany 1.3.2 and
1.4 releases. The complete timeline of available and future plans is given in
the [Tuscany Web 2.0 Roadmap|http://tuscany.apache.org/sca-java-roadmap.html].
Note also that the RSS binding support is similar to the [Tuscany Atom Binding
Support|http://tuscany.apache.org/sca-java-bindingatom.html] in both syntax and
function.
h3. Using the Tuscany RSS binding
The primary use of the RSS binding is to provide support for collections that
can be shared in a distributed fashion. Examples of shared collections includes
shopping carts, telephone directories, insurance forms, and blog sites. These
collections of items can be added, retrieved, updated, and deleted using the 4
basic actions of the HTTP protocol:
* POST (create or add)
* GET (retreive or query)
* PUT (update)
* DELETE (destroy or remove
The simplest way to use the Atom binding is to declare a collection as a
service and provide an HTTP address where one can access the service. This
service is declared in an SCA composite file which describes the SCA domain.
{code}
<service name="customer" promote="CustomerCollection">
<tuscany:binding.rss uri = "http://localhost:8084/customer"/>
</service>
{code}
The service can be implemented in Java or any of the the Tuscany implementation
types. For example, here is a way to create an implmentation for the above
CustomerCollection service as the Java implementation.
{code}
<component name="CustomerCollection">
<implementation.java
class="org.apache.tuscany.sca.binding.feed.CustomerCollectionImpl"/>
</component>
{code}
A collection that uses the RSS binding usually implements the Collection
interface given in the package org.apache.tuscany.sca.binding.atom.collection.
This interface declares the basic access methods mentioned above (post, get,
put, and delete), and the data types on the methods are expressed as RSS
SyndFeed and SyndEntry objects. This shows the basic methods of the RSS
Collection interface in Tuscany:
{code}
public interface Collection {
SyndFeed getFeed();
SyndFeed query(String queryString);
{code}
It is up to the developer or implementer of the shopping cart, telephone
directory, or blog site to provide the code that implements the Collection
interface. The developer or implementor also provides the code that translates
from the business objects (shopping cart items, directory entries, insurance
forms, blog articles) to the Atom model objects Feed and Entry.
One of the features of using this binding is that your business objects
(shopping cart items, directory entries, insurance forms, and blog articles)
can now be easily published and shared by the many RSS supporting tools such as
feed readers, web browsers, and syndication aggregation. In other words, people
can access your collection most anywhere on any device.
h3. Example
Continuing with the CustomerCollection example shown above, let's see how to
implement one of the common access methods. In this case, let's look at the get
method in a client and how one would display the items of a collection. When
you declared your RSS binding in your SCA composite, you also provided a uri
for your collection. Using a web browser or other device, a user performs an
HTTP get request to this uri. The HTTP response for your get request contains a
body which has the RSS SyndFeed seruialized as a SyndFeed. You may access this
SyndFeed using Java, and display or present to a user the contents of the RSS
feed.
{code}
SyndFeed feed = resourceCollection.getFeed();
for (Object o : feed.getEntries()) {
SyndEntry e = (SyndEntry)o;
System.out.println("id = " + e.getUri() + " entry = " +
e.getTitle());
}
{code}
Much of the code consists of converting from a RSS SyndFeed or SyndEntry to a
business data model and storing to a collection.
Tuscany uses Java Project ROME to provide a model for RSS data. Please see
[Project ROME |https://rome.dev.java.net/] for the Java methods to access RSS
SyndFeeds and SyndEntries, and how to easily convert these Java objects to and
from XML.
h3. Other Features of the Tuscany RSS Binding
In contrast to the Tuscany Atom binding, the Tuscany RSS binding does not
provide:
* Data caching based on ETag and LastModified header fields.
* JavaScript Object Notation (JSON) alternative to XML feeds and entry data.
* Service document for site introspection.
* Full featured JavaScript client for easy client side programming.
See the [Tuscany Atom Binding
Support|http://tuscany.apache.org/sca-java-bindingatom.html] for a description
of these features and how users may get more benefits from the Atom binding.
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