Developing J2EE applications - IntelliJ IDEA in Action - page 385

In case of a separate .tld file, make sure that its containing folder is regis-
tered in the Web Resource Directories list and mapped to the / WEB-INF
deployment directory or one of its subfolders.

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In case of a JAR , once it's added to the Classpath, IDEA resolves all refer-
ences to the tag library and provides appropriate code completion and
highlighting. But for the deployment purposes (to avoid possible runtime
errors), you may need to specify packaging method and deployment path
for that JAR in the Modules and Libraries to Package list.

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In rare cases, when you have the accompanying .tld file detached from its
JAR , you need to configure references for file and JAR separately, as
described earlier.

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IDEA 5.0 supports the new JSP 2.0 tag files format. This format makes it easy to
add new tags without writing a line of Java code, mucking with the TLD , and so
forth. IDEA can locate your tags through the direct reference to their containing
folder in the tagdir attribute of the taglib directive. IDEA supports both the
scriptlet-based .tag and XML .tagx formats. The editor assists you in including
these through code completion and identifies invalid usage or syntax errors.
IDEA 5.0 fully supports the XML version of JSP files known as JSP documents ,
which have the file extension .jspx, including those features of the format new to
JSP 2.0. In JSP documents, a JSP is represented as well-formed XML code, and any
embedded HTML must be well-formed XHTML . When you're working in JSPX
documents, you have both the benefits of IDEA 's XML editing features as well as
the Java code completion and other aspects of the traditional JSP editor. JSPX
documents have their own file type designation and code style settings.

This TLD file, which describes the tags in the library and defines their attributes,
can be located by IDEA through a variety of means defined in the JSP specifica-
tion. We'll describe the most common ones momentarily.
When you use a tag library in JSP , you must specify the tag library's URI and its
prefix on each JSP page in which you wish to use it. Both direct and indirect URI
references can be used, as shown in the following examples:

<%@ taglib uri="my_descriptor.tld" prefix="descriptor" %>
IDEA looks for my_descriptor.tld file in all web resource directories that are
mapped to the deployment directory / WEB-INF .