計(jì)算機(jī)外文翻譯--使用自定義標(biāo)簽庫和jsp標(biāo)準(zhǔn)標(biāo)簽庫

1、外文原文Chapter 7. Using Custom Tag Libraries and the JSP Standard Tag LibrarySo far we've covered the JSP basics—the primary parts of a page and installation and execution of a page—and how to use beans to dynamically

2、add content to a page. Before we start working on real applications, let's turn to another fundamental JSP feature: custom tag libraries.Custom tag libraries are, in my opinion, what make JSP so powerful. They make i

3、t possible for page authors to embed pretty much any logic in a page using familiar, HTML-like elements. In this chapter, we take a close look at what a custom tag library is, how to install and use it, and what the JSP

4、Standard Tag Library (JSTL) brings to the table.7.1 What Is a Custom Tag Library?The JSP standard actions, such as the and actions used in Chapter 6, are HTML-like elements for commonly needed functions in a JSP page:

5、creating beans, accessing bean properties, and invoking other JSP pages. But there's a lot more you want to do that isn't covered by the standard actions.To extend the set of action elements a page author can use

6、 in the same familiar way, new actions can be developed, either by a programmer as Java classes or by a page author as tag files (a special kind of JSP file). In either case, these actions are called custom actions. A cu

7、stom action can do pretty much anything: it has access to all information about the request, it can add content to the response body as well as set response headers, and it can use any Java API to access external resourc

8、es such as databases, LDAP servers, or mail servers. The way the JSP container interacts with a custom action also makes it possible for a custom action to conditionally process its body and to abort the processing of th

9、e rest of the page. Custom actions can be created for application-specific functions to make it easier for page authors to develop the JSP pages. Some typical examples are shown later in this book.new MixedMessageBean(

10、);// Attributesprivate String category;public void setCategory(String category) {this.category = category;}public void doTag( ) throws IOException {mmb.setCategory(category);JspWriter out = getJspContext().getOut( );ou

11、t.println(mmb.getMessage( ));}}For each attribute supported by the custom action, the tag handler must implement a bean-style setter method, such as the setCategory( ) method in this example. The container calls methods

12、 defined by the SimpleTag interface, such as the doTag( ) method, to let the tag handler do its thing.So why is it called a custom tag library if it's a collection of custom actions? Using formal XML terminology, one