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This essay developed out of conversations I've had with several other programmers about why Java smelled suspicious. It's not a critique of Java!
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" Java provides the industry - software companies and customer alike , an opportunity to create a true open computing environment where software is portable,
and customers benefit from increase competition. "
Java and the Future
December 1, 2008-LEJB 3.1: EJB New and Improved!
The EJB 3.0 specification was a huge improvement from what you were used to in the early versions of EJB. Available as an early draft, EJB 3.1 has many more features and is even easier to use.
December 1, 2008-Should Java Assert that Network I/O Can't Occur on the UI Thread?
Doing network I/O on the user interface (UI) thread is bad. Most developers know that and can tell you why; unfortunately, it's still done.
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EJB 3.0 Message-Driven Bean
A message-driven bean is an enterprise bean that allows J2EE applications to process messages asynchronously. It acts as a JMS message listener, which is similar to an event listener except that it receives messages instead of events. The messages may be sent by any J2EE component--an application client, another enterprise bean, or a Web component--or by a JMS application or system that does not use J2EE technology.
Message-Driven Beans Different from Session and Entity Beans?
The most visible difference between message-driven beans and session and entity beans is that clients do not access message-driven beans through interfaces.
- A message-driven bean's instances retain no data or conversational state for a specific client.
- All instances of a message-driven bean are equivalent, allowing the EJB container to assign a message to any message-driven bean instance. The container can pool these instances to allow streams of messages to be processed concurrently.
- A single message-driven bean can process messages from multiple clients.
Applications that use JMS are called JMS clients , and the messaging system that handles routing and delivery of messages is called the JMS provider . A JMS application is a business system composed of many JMS clients and, generally, one JMS provider. A JMS client that sends a message is called a producer , and a JMS client that receives a message is called a consumer . A single JMS client can be both a producer and a consumer.
JMS provides two types of messaging models: publish-and-subscribe and point-to-point . The JMS specification refers to these as messaging domains. In JMS terminology, publish-and-subscribe and point-to-point are frequently shortened to pub/sub and p2p (or PTP), respectively.