5.2.2

Location of Java Classes

The request time Tag handler classes and the translation time TagExtraInfo classes are just 

Java classes.  In a Web Application they must reside in the standard locations for Java 

classes: either in a JAR file in the WEB INF/lib directory or in a directory in the WEB INF/

classes directory.

The previous rule indicates that a JAR containing a packaged tag libraries can be dropped 

into the WEB INF/lib directory to make its classes available at request time (and also at 

translation time, see Section 5.3.2).  The mapping between the URI and the TLD is explained 

further below.

5.2.3

Tag Library directive

The 

taglib

 directive in a JSP page declares that the page uses a tag library, uniquely 

identifies the tag library using a URI and associates a tag prefix that will distinguish usage of 

the actions in the library.

If a JSP container implementation cannot locate (following the rules described in 

Section 5.3.1) a tag library description for a given URI, a fatal translation error shall result.

It is a fatal translation error for the 

taglib

 directive to appear after actions using the prefix 

introduced by the 

taglib

 directive.

5.3

Tag Library Descriptor

The Tag Library Descriptor (TLD) is an XML document that describes a tag library. The 

TLD for a tag library is used by a JSP container to interpret pages that include 

taglib

directives referring to that tag library. The TLD is also used by JSP page authoring tools that 

will generate JSP pages that use a library, and by authors who do the same manually.

The TLD includes documentation on the library as a whole and on its individual tags, version 

information on the JSP container and on the tag library, and information on each of the 

actions defined in the tag library.

Each action in the library is described by giving its name, the class for  its tag handler, 

optional information on a 

TagExtraInfo

 class, and information on all the attributes of the 

action. Each valid attribute is mentioned explicitly, with indication on whether it is 

mandatory or not, whether it can accept request time expressions, and additional information.

Chapter 5

Tag Extensions

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