J2EE basic knowledge (not completed, not before, not substance)
Today started learning J2EE, J2EE accumulated knowledge!
Have a reference book called "Guide to J2EE network programming standards," on the content inside is very good, huh, when the Internet to see when this book to see that the name is also the underlying network and related things, Socket explain what that is like and TCP / IP communication protocol Dongdong, did not want to, then I do not know how to download it and sent it opened read, Guihe Hey, I want to see the original is the Dongdong, generally see J2EE basic knowledge of the previous chapter, basically on the macro level of J2EE with a clear understanding (not joking, really, because jade dragon was in school, learn C + + and after graduation spent two years as Delphi and ASP development, the design of the system to understand and not the Henben 
), The J2EE basic knowledge on the basis of this book, and began to learn, start to accumulate their knowledge well.
Well, if the beginners are interested can go to download their own look at this book, jade dragon will be listed here J2EE basic knowledge in the knowledge points to facilitate their learning and mastering. Remember, these write-NEE is to the dragon with their own learning, and as long as jade dragon will be able to understand the other person? Hei hei, a Kanbukan understand, I am of Pishi
First, the core of the J2EE there are two: One is the ideological stratification and the other is the ideological component
J2EE will function in accordance with a system, divided into four independent layers, they are:
Data layer (layer also called EIS), business layer, presentation layer, layer.
J2EE hierarchical diagram
Data layer (also called EIS layer)
Business Layer
Presentation layer
Customer -
√
√
√
Component
√
√
√
Vessels
√
√
√
Server
As shown below, the data layer (layer also called EIS), business layer, presentation layer, layer, which is four tiered system of tiered, four layers are mutually independent relationship.
One business layer, presentation layer, layer, layer and the three into their components, containers, three of the server. The containers often with the server has been integrated into an underlying platform used to provide the underlying services. So J2EE developers no longer concerned with the bottom of the relevant operating platform, and just focus on functional modules and business processes - EJB component of the development, and then deployed to the server components on it.
Components must be running in the containers, and containers must be running on the server (usually container and the server has been integrated)
Server to provide services for containers, and containers for EJB components provide services.
J2EE must seize the study of the two ideas and views so that they will not feel the technical confusion.
Second, J2EE Design of the three kinds of structures and components
J2EE structure 1
J2EE architecture 2
J2EE structure 3
Hierarchical
Component
Client Applications
Dynamic HTML pages
Dynamic HTML pages
,
Client machines
Client components: the client components and procedures Applet components
JSP pages
JSP pages
WEB -
J2EE server
WEB components: JSP Servlet component or components
EJB
EJB
Business Layer
Business logic components: EJB component
Database
Database
Database
Data layer (also called EIS layer)
Database Server
On the Plan has been very clear that the J2EE Design of the three kinds of structure, and show that the use of the corresponding components, which WEB components and business logic components of the design is the focus of J2EE.
Third, the J2EE container and the server
Components can operate independently, must be running in the containers, that is, the components must be deployed to boost container.
The so-called deployment, the configuration is designated containers, containers should be told what kind of services to the components in order to guarantee the normal operation of components.
Special Note: 1) between the components and parts can not communicate directly, and they must be associated with the exchange of information through the containers to carry out.
2) attention to the "callback containers," the concept of components in containers running on is, in fact, components of the containers callback process that is to say, components can be called the bottom of containers to provide services (can be termed 'positive Calling '), components and containers in turn calls the function, that is, "correction."
3) between the components and containers through the "interface" of the call, access interface components called bottom containers, container function call interface components services.
4) components in the definition of methods for users is not the definition, but the definition of containers for the callback interfaces; user is not directly call components of the method must be adopted to achieve callback containers, the containers will be automatically Component identification and call the method, completed application functions. This is, understand the need to pay particular attention to time, is also very important.
Fourth, in the J2EE components, the relationship between the container and server
Components and containers were one-to-one relationship, what types of components are the types of containers: WEB WEB containers are mapping components; EJB components are one-to-one EJB containers can not be deployed to the components WEB EJB containers forward, nor can EJB components deployed to boost WEB containers, because they are not related to the same interface.
Server does not mean that the meaning of a specific computer hardware, but rather refers to a service provider process, which is easier for beginners mixed.
Vessel and between the call server is not visible and communications, and they have been integrated manufacturers, programmers can not be visible.
J2EE programmers to solve the problem is to achieve the components and containers between the call problem.
