Custom Tag---legacy tag processor

1. traditional Tag Processor API

2. Traditional tag processor life cycle

3. Traditional marker life cycle depends on return value

Unlike a simple tag processor, a container can reuse a traditional tag processor object, so it is best to reset the value of the instance variable in doStartTag (), otherwise this code may only work correctly for the first time.

4. If you need to access the body content

If you need to access the body content, the tag processor needs to extend Bodytagsupport instead of TagSupport. Based on Bodytag, you get two new methods, and doStartTag () also has a new return value: eval_body_buffered. The tag has a new life cycle:

Custom Tag---legacy tag processor