Best way to know is to look at the java source file generated for a JSP that uses custom tags/beans. I found it at this location on my workstation $tomcat_home\work\Catalina\localhost\<appname>\org\apache\jsp\HelloWorld_jsp.java
I have an example of SimpleTagSupport here.
Given a tag class simplemodel.HelloWorldTag extending SimpleTagSupport, the java source translated from jsp looked like this:
Given what we know about the lifecycle, the container has to a) create an instance of the tag - line 6 b) set the jsp context on the tag object line - line 7 c) call the setParent if it is nested and call the set attributes if they are used in the invocation - not applicable d) invoke the doTag method of the tag's class - line 8
Please note that the actual source might vary depending on the vendor, this is just an example with tomcat 5.5
For java beans, the use bean tag is translated as below: