JSP has a lot to learn, here we introduce the JSP, and BEAN, including the introduction Servlet used to write the business layer is very strong and so on.
Simply put, SUN first developed Servlet, more robust functionality, system design is also very advanced, but, it outputs HTML statement or CGI use the old way, is a one output, therefore, is very inconvenient to write and modify HTML. SUN ASP was introduced similar to the mosaic type of JSP, the JSP TAG statement embedded into HTML, so that would greatly simplify and facilitate the web design and modification.
New network languages such as ASP, PHP, JSP are Inlaid SCRIPT language
Three layers from the network point of view, a network project for at least three layers: data layer, business layer, presentation layer. Of course, can also be more complex. Servlet used to write the business layer is very powerful, but very convenient for the written presentation layer. JSP is written primarily for the convenience of presentation layer is designed. Of course, you can write business layer. Was used to ASP, PHP, CGI friends, often unconsciously, the presentation layer and business layer mixed. Like that in front of friends, to process information into the JSP in the database, in fact, it should be placed in the business layer.
According to SUN own recommendation, JSP that should be kept with the presentation layer only related to the East, that is, only put part of the output HTML page. And all the data calculation, data analysis, database connection handling, all belong to business layer, should be placed in JAVA BEANS. Called by JSP JAVA BEANS, to achieve the integration of two.
In fact, Microsoft recently introduced DNA technology, simply, is that ASP + COM / DCOM technology. And JSP and BEANS completely similar to the presentation layer of all completed by the ASP, all the business layer from the COM / DCOM completed. By calling, to achieve integration.
Why should we use these components technology? As simple ASP / JSP language is very inefficient implementation, if there is a large number of user clicks, pure SCRIPT language quickly reached the limit of his capabilities, and component technology can significantly improve the function of the ceiling, accelerate the pace of implementation.
On the other hand, pure SCRIPT language presentation layer and business layer will be mixed, resulting in changes inconvenient, and the code can not be reused. If you want to change a place, often involving dozens of pages CODE, with component technology will only change components on it.
In summary, Servlet is an early imperfect product, writing a good business layer, presentation layer was very foul, and two mixed.
Therefore, the introduction of JSP and BAEN, written with JSP presentation layer, using BAEN written business layer. SUN is the meaning of their own future alternative use JSP Servlet.
However, this is not to say, learned the Servlet useless, in fact, you should from the Servlet entry, then the JSP, then the JSP and BEAN.
Stress: Studies of the JSP, and will not integrate with JAVA BEAN, virtually no school. We spend more effort on the JSP and BEAN.
Add a few:
We can see that when the ASP + COM, and JSP and BEAN are using component technology, all of the components are compiled first, and the presence of memory, and rapid implementation. Therefore, we always blow the Servlet / JSP first compiled in memory, speed of implementation, there is no advantage.
Conversely, ASP + COM + IIS + NT tightly integrated and should have a greater speed advantage showed. Moreover, ASP + COM + IIS + NT development efficiency is very high, although many BUG. So why use JSP and BEAN? Because JAVA is promising. Microsoft spin-off, the operating system will be independent warlords, the application software developers will find a common development language for development, JAVA domination time comes. If Microsoft is successful spin-off, separate the applications from the company will become the new leader in JAVA. The bulk of the current JAVA SUN and IBM are stagnant, disappointing. Hope that the new company will inject new life. However, the new company is likely to start the old SUN JAVA standards war, the two sides to develop their own standards, influence boast JAVA platform.
In addition, the machine is now faster and faster, JAVA speed disadvantage can be overcome soon.
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