Solutions for Java developers
04/14/09
By Adam Bien
The crucial artifact in any SOA is an exposed service. A service
can be considered as a contract with significant business value.
A clear relationship should exist between the service contract
and a business requirement, a use case, or even a user story. A
service can be realized as a single action or a set of cohesive
actions. For example, anOrderServicemight comprise a single
action that performs the actual order, or a group of related
operations that also include canceling the order and receiving
the order status. An SOA does not reveal any details about how a
service must be implemented; it aims for services to be
technology- and even location-agnostic.
SOA principles can be mapped to Java EE artifacts. The most
important ingredients in a Java-based SOA implementation are
interfaces and packages. Everything else is only a refinement,
or design. Only one artifact in the language -- a plain Java
interface -- meets the requirements of a service contract. It is
often used to decouple the client from the service
implementation. It can also be used to expose the functionality
of a component.
Component based design (CBD) is SOA's evolutionary predecessor.
Component contracts are comparable to SOA's services, except for
their heavier dependence on particular technology and general
lack of operations-related metadata -- such as service-level
agreements (SLAs) -- or strong governance principles
http://www.javaworld.com/podcasts/jtech/2008/071508jtech.html .
A component is built on themaximal cohesion, minimal
couplingprinciple. A component should be highly independent of
other components, and the implementation should consist of
related (cohesive) elements. In a Java EE SOA implementation, a
component is a Java package with these strong semantics. The
package's functionality is exposed with a single interface, or
in rare cases a few interfaces.
Read more: Lean SOA: The essential complexity
http://www.networkworld.com/nljavaworldsente191680
1. EJB 3: From legacy technology to secret weapon
http://www.javaworld.com/javaworld/jw-10-2008/jw-10-ejb3.html
2. Dan Diephouse: SOA governance with Mule Galaxy
http://www.javaworld.com/podcasts/jtech/2008/071508jtech.html
3. SOA & Web services research center
http://www.javaworld.com/channel_content/jw-webserv-index.html
Alex Miller is a respected Java concurrency and scalability
enthusiast who works on Terracotta, an open source, Java-based
clustering system. In this talk with Andrew Glover, Alex
demystifies Terracotta, explaining the programming magic that
enables enterprise customers to run 50 to 100 JVMs on a single
application server instance. Alex also talks about Terracotta's
"sweet spot" -- storing session data off of the database -- and
Terracotta 3.0, which promises new features that he says will
eliminate certain scalability barriers.
Listen up: Alex Miller: Enterprise clustering with Terracotta
http://www.networkworld.com/nljavaworldsente191681 1. Dustin Marx: Exporting POJO via JMX and Groovy
http://www.javaworld.com/community/?q=node/2781
2. Charles Nutter: JRuby Moves to Git
http://www.javaworld.com/community/?q=node/2780
3. Esther Schindler: When the Job Changes But the Programmer
Doesn't http://www.javaworld.com/community/?q=node/2779
You've hit the tip of the iceberg: Read more in JW Blogs
http://www.javaworld.com/community/
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This newsletter is sponsored by Dell
More Productive Mobile Computing
This webcast details the key elements and best practices
essential to planning a successful large-scale migration to
Windows Vista so you can immediately begin to reap the benefits
of improved security, lower operating costs and more productive
mobile computing.
http://adserver.fattail.com/redir/redirect.asp?CID=296006
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