Struts 2 is a popular Java web application framework that provides a set of components to help developers build robust and scalable web applications. Here are some of the key components of Struts 2:

1. Actions: Actions are Java classes that are responsible for handling HTTP requests and generating responses. Actions contain business logic and are typically responsible for performing data validation, accessing a database, or calling a service to generate a response.

2. Results: Results are responsible for generating the response content and returning it to the client. Struts 2 comes with a variety of pre-built result types, including JSP, Velocity, and FreeMarker.

3. Interceptors: Interceptors provide a way to add cross-cutting concerns to an application, such as logging, authentication, or transaction management. Struts 2 provides a number of built-in interceptors, and developers can also create their own custom interceptors.

4. Value Stack: The Value Stack is a collection of objects that are made available to the view layer for rendering. These objects can include the action, any parameters submitted with the request, and any objects added to the Value Stack by interceptors.

5. Tags: Struts 2 provides a set of custom tags that can be used in JSP pages to generate HTML forms, links, and other user interface components. These tags simplify the process of generating HTML and ensure that the HTML is compliant with web standards.

6. Configuration: Struts 2 is highly configurable and provides a number of ways to customize its behavior. Developers can use XML files or annotations to define actions, results, interceptors, and other components of the application.

Overall, these components make Struts 2 a powerful and flexible framework for building web applications in Java.