Java EE applications

javaee , from just beginning to see " EJB " when you want to write, always feel that they know too little, it is not worth mentioning, too deficient (I am too modest) ... haha ha . To later work has been using javaee related technologies. Open-Source popular frameworks (ssh and lang= >spring "en-us" spring as the core Family things) were almost the same. At work javaee Enterprise-class stuff is like a fool. Look back to the summary to avoid yourself really become a fool.

Starting with "Components" (component), it is not known when people want software development to be assembled like a child's building blocks. One concept that comes up is "components," which, in a professional sense, is "a component is a self-contained, reusable unit of software that can be integrated into an application." It is more straightforward to say that a building block is able to complete a task independently, and that blocks can be used in multiple places (think of the screws, nuts, think of the engine, the transmission is believed to help readers understand the concept of "components"). The simplest form of a component in Java is JavaBean. We are usually called beans.

It is squalling to hear the word that the person who has just started learning. Pig, Pig awareness can , pig just the iguana , mu mother, net Altar Messenger, Tian Peng a bunch of names in the end is not a pig!

What Bean,Javabean , is not the class in Java .

Squalling to squalling, different names in different places are meaningful.

The Marshal of the Sky Peng refers to this pig in heaven officials when the name, Pig is the pig with the Tang priest after the name, pig just the iguana is the pig in the Gao period of the name ... It seems that far. In short, the difference between the meaning of the name and the things to be reacted to is not blinders. Do you understand the name of JavaBean now?

Within the enterprise, components are more focused on implementing business services. Define the contract for the component at the same time based on the business operations that the component can run. The standard component model of Java EE is the EJB model, which defines the way in which packaging, deployment, and interaction with self-contained business services are made.

The type of EJB determines the contract that needs to interact with it. The session Beanuses a standard Java interface to define a collection of business methods that can be invoked. The behavior of a message-driven Bean(message-driven bean) depends on the type of message and format that the Bean is intended to accept.

The above paragraph is very official. summed up into the ground gas is in the Java EE domain different types of components have their own specifications, these components can be in accordance with their own specifications to complete the business services.

Ah. Good abstraction ...

It is optional to use the component model in our usual development, and in general the container service that can be used with the session Bean is also available Servet.

As a result, most Web applications today completely shun EJBs, directly from Servet to the database.

This has led to the vigorous development of spring 's spring family and the open source framework of the spring family.

When using components we , where the business service is in the component model. And it means that the service layer is above it (you might be thinking mvc . As far as I understand it now ejb and mvc is not either included nor tied. They are ... Again later).

now very much Span lang= "en-US" >web application does not select ejb because of the complexity of ejb in history. As opposed to ejb2 , ejb3 absorbs the idea of a very much open source framework, which can now be said to be very easy. As the problem of complexity is solved, people begin to reap the benefits of a defined set of business services brought to the application. (ejb is not as complicated as before, x , and began to use, ho haha Ha ).

!--[if!supportlists]-->l  ! --[endif]-->oose couping ). Organize business logic with the idea of components, and make it easier to write loosely coupled code.

l Dependency Management (dependencymanagement). Whether it is an annotation or a configuration file. Containers and people (mostly people) can be at a glance.

!--[if!supportlists]-->l   The!--[Endif]--> Life cycle Tube ifecyce management ). Components are defined and managed by the container to handle the acquisition and deallocation of resources uniformly.

l Declarative Container Services (decarativecontainerservice). The business method of the component is intercepted by Application server. So concurrency, transaction management, security, and remoting do not need to distract developers from too much effort.

l Portability (portabiity). An application can run under Tomcat so gassfish can also be used. There's no problem with webogic , so it's not too much of a problem for Jboss to talk about IIS .

l Scalability and Reliability (Scaabiity and reiabiity).

Application server is designed to ensure that the components are effectively implemented for scalability management. Depending on the type of component and server configuration, business operations implemented using components can retry failed method calls, or even fail over to a server on the cluster (consider RMI).

Java EE applications