jsp和数据库外文文献原文及翻译
Dynamic Web-based data access using JSP and JDBC technologies
This article discusses using the JSP and JDBC technologies to integrate static, dynamic, and database content in Web sites. For the purposes of simplicity and illustration, the JSP pages here use short scriptlets to expose the JSP developer to the underlying JDBC concepts instead of hiding them in custom tags. The author introduces a key design approach that integrates JavaBeans components with JDBC, similar to the way that JavaServer Pages technology already uses beans with HTTP. He also provides code for implementing this integration.
Building on the Java Servlet technology, JavaServer Pages (JSP) technology is the core server-side Java architecture for generating dynamic content. One source of dynamic content is the relational database. To manage everything from online communities to e-commerce transactions, Web sites use relational databases to store all sorts of information: catalog items, images, text, data about registered members, and so on. This article discusses the application of JSP technology to relational databases through Java Database Connectivity (JDBC). JDBC is the means by which Java programs work with relational databases.
To get the most out of this article, you should be familiar with JDBC and SQL.
JDBC basics
JDBC is the bridge between Java code and SQL databases. The primary JDBC objects represent connections to a database and the statements performed using those connections. The two basic kinds of statements used with a relational database are 原文请找腾讯752018766优,文-论'文.网http://www.youerw.com/ like a Web server, you want to reuse connections whenever possible. Such reuse is called connection pooling.
In real life, JDBC code is not this simple; exceptions and warning conditions need to be handled. Listing 2 illustrates the same JDBC example but adds handling for JDBC exceptions and warnings. In this example, exceptions and warnings are simply logged and, in the case of exceptions, we abort the operation. However, the finally{} clauses ensure that resource cleanup proceeds.
The actual processing of the results is only hinted at here; we'll be looking at it more closely later on in this article. If we were performing a database update instead of a query, we would replace the while loop with the following:
int count = statement.executeUpdate(sqlUpdate);
The executeUpdate() method returns the number of rows affected by the update statement.
If the material in these code listings seems unfamiliar, you may want to spend some time reviewing some of the JDBC tutorial information found in the Resources section.
Using JDBC with JSP pages
So how do we combine JDBC and JSP technologies so that our dynamic content comes from a database?
As a general rule, good JSP practice suggests that you separate presentation from model behavior. This is analogous to the Model-View-Controller (MVC) paradigm in object-oriented programming. One reason for the separation is that applications based on JSP technology are likely to have the Model and Controller components authored by programmers, whereas the View components will be authored by page designers. In the case of JSP application architectures, the role of View, whose responsibility is presentation, is handled by a JSP page. The role of Controller, whose responsibility is reacting to requests, is often played by a servlet, but many JSP practitioners are coming to realize the advantages of using a JSP page in the Controller role. The role of Model, whose responsibility is modeling the behavior of application entities, is typically played by JavaBeans components.1905