Difference between <%! %>,<% %>,<%= %>

The variables and methods declared in <%! %> exist as attributes and methods of the class. Methods
cannot be declared in <% %>, while the variables declared in <% %> are used as internal attributes of the method _jspService. It is to execute a piece of code (remember to add ";" after the code)
<%= %> just presents a certain value (such as a string), or is used to bind to a variable