Chapter 7. Building JSP Pages Using the Expression Language (EL)
Given a scenario(方案;情況;概要), write EL code that accesses the following implicit variables including: pageScope, requestScope, sessionScope, and applicationScope, param and paramValues, header and headerValues, cookie, initParam and pageContext.
There are several implicit objects that are available to EL expressions used in JSP pages. These objects are always available under these names(講的是EL的隱含對象和簡單的說明)

Chapter 9. Building JSP Pages Using Tag LibrariesFor a custom tag library or a library of Tag Files, create the 'taglib' directive for a JSP page.
The set of significant(有意義的, 重大的, 重要的) tags a JSP container interprets (解釋, 說明)can be extended through a tag library.

The taglib directive in a JSP page declares that the page uses a tag library, uniquely(獨特地,唯一地,珍奇地) identifies the tag library using a URI and associates(使發生聯絡, 使聯合) a tag prefix that will distinguish usage of the actions in the library.

If a JSP container implementation cannot locate a tag library description, a fatal translation error shall result.

It is a fatal translation error for the taglib directive to appear after actions or functions using the prefix.

In the following example, a tag library is introduced and made available to this page using the super prefix; no other tag libraries should be introduced in this page using this prefix. In this particular case, we assume the tag library includes a doMagic element type, which is used within the page.

Given a design goal, use an appropriate(適當的) JSP Standard Tag Library (JSTL v1.1) tag from the "core" tag library.
The center of JSTL is the core taglib. This can be split into five areas:

General purpose

Variables support



URL Related

To use the core library, use the following directive:

<%@ taglib prefix="c" uri="" %>The prefix attribute specifies(指定,規定,確定) the prefix used in the tag name for a particular library. For example, the core library includes a tag named out. When combined with a prefix of c, the full tag would be <c:out>. You are free to use any prefix you like, but you must use different prefixes for each of the four standard tag libraries.

You must also put the corresponding(相應的) .tld file for each tag library in your /WEB-INF directory and use the taglib element in your web.xml file to include the tag library:

<taglib>    <taglib-uri></taglib-uri>    <taglib-location>/WEB-INF/tld/core.tld</taglib-location></taglib>

General purpose tags.

The general-purpose tags let you display variable values, and enclose(封閉,密封;封裝,包圍) a group of tags within a try-catch block.

The <c:out> action provides a capability(能力, 效能, 容量)similar to JSP expressions such as <%= scripting-language-expression %> or ${el-expression}. For example:

You have <c:out value="${sessionScope.user.itemCount}"/> items.

The <c:catch> action allows page authors to handle errors from any action in a uniform(統一的, 相同的) fashion, and allows for error handling for multiple actions at once. <c:catch> provides page authors with granular(粒度[狀) error handling: Actions that are of central importance to a page should not be encapsulated(密封) in a <c:catch>, so their exceptions will propagate to an error page, whereas actions with secondary importance to the page should be wrapped in a <c:catch>, so they never cause the error page mechanism to be invoked(調用). The exception thrown is stored in the scoped variable identified by var, which always has page scope. If no exception occurred, the scoped variable identified by var is removed if it existed. If var is missing, the exception is simply caught and not saved.

<c:catch [var="varName"]>nested(嵌套的) actions</c:catch>這部分基本上涉及了JSTL的所有內容。





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