How do you use scriptlets in JSP?

Scriptlet in JSP is a special tag used to embed Java code in JSP pages. It is used by wrapping Java code in <% and %> tags within the JSP page, as shown below:

<%
// 在这里插入Java代码
int num1 = 10;
int num2 = 20;
int sum = num1 + num2;
%>

In the example above, the code block between <% and %> is called a scriptlet, where you can write any Java code. This code will be executed when the JSP page is converted to a Servlet and then output the results to the client. It is important to note that scriptlets should not be heavily used in JSP pages and it is advised to avoid writing excessive business logic in JSP in order to improve the maintainability and readability of the page.