This simple tag handler extends SimpleTagSupport (a class you’ll see in the next chapter), and implements two key methods: doTag(), the method that does the actual work, and setUser(), the method that accepts the attribute value.
Java class that does the tag work
Custom tag handlers don’t use custom method names!
With EL functions, you created a Java class with a static method, named the method whatever you wanted, then used the TLD to map the actual method <function-signature> to the function <name>. But with custom tags, the method name is ALWAYS doTag(), so you never declare the method name for a custom tag. Only functions use a method signature declaration in the TLD!