A custom tag is made up of two components:
A Java class file that implements the tag
An entry in a Tag Library Descriptor (TLD) file that defines the tag's name, its implementing Java class, and additional information necessary to deploy and use the tag
Using a custom tag requires a reference to the Tag Library Descriptor (TLD) at the start of the JSP. Multiple Tag Libraries can be used on the same Web page. After the TLD has been referenced, the custom tag from the TLD can be used like any other JSP tag.
To start learning to write and use TagLibs, you will implement a very simple custom tag that writes “Hello World” onto your Web page. This isn't a good use of a custom tag, but it will help you ...