Is it possible to define a class inside a JSP page?

Yes, it is possible by using the <%!...%> tag, which is called a "declaration".

<%!
    // Definition of a static class
    public static class MyStaticHelper {
        public static String sayHello(String name) {
            return "Hello, " + name + "!";
        }
    }

    // Definition of a non-static (inner) class
    public class MyInnerHelper {
        public String greet(String name) {
            return "Greetings from inner class, " + name + "!";
        }
    }
%>

<%
    // Using the static class
    String greeting = MyStaticHelper.sayHello("World");
    out.println(greeting);

    // Using the non-static class
    MyInnerHelper innerHelper = new MyInnerHelper();
    String innerGreeting = innerHelper.greet("Java");
    out.println(innerGreeting);
%>

However, this approach is considered bad practice for the following reasons:

• Low readability and maintainability: Mixing logic (Java code) and presentation (HTML, JSP) makes the code difficult to understand and modify.
• Testing difficulties: Code defined in a JSP declaration is harder to isolate for unit testing.
• Reusability: A class defined in one JSP is not accessible from other JSPs or other parts of the application.
• Violation of MVC principles: JSP should be responsible for data presentation, not for business logic or class definitions.

A more preferred approach is to define classes in separate .java files and use them in JSP via import or through JavaBeans and EL (Expression Language).