The JavaServer Pages API allow you to define custom JSP tags that look like HTML or XML tags and a tag library is a set of user-defined tags that implement custom behavior.
The taglib directive declares that your JSP page uses a set of custom tags, identifies the location of the library, and provides means for identifying the custom tags in your JSP page.
The taglib directive follows the syntax given below −
<%@ taglib uri = "uri" prefix = "prefixOfTag" >
Where, the uri attribute value resolves to a location the container understands and the prefix attribute informs a container what bits of markup are custom actions.
You can write the XML equivalent of the above syntax as follows −
<jsp:directive.taglib uri = "uri" prefix = "prefixOfTag" />
When you use a custom tag, it is typically of the form <prefix:tagname>. The prefix is the same as the prefix you specify in the taglib directive, and the tagname is the name of a tag implemented in the tag library.
For example, suppose the custlib tag library contains a tag called hello. If you wanted to use the hello tag with a prefix of mytag, your tag would be <mytag:hello> and it will be used in your JSP file as follows −
<%@ taglib uri = "http://www.example.com/custlib" prefix = "mytag" %> <html> <body> <mytag:hello/> </body> </html>
We can call another piece of code using <mytag:hello>. We will see how to develop our custom tags and how to use them in JSP - Custom Tags tutorial.