What is the difference between Struts2 and Spring?

Here are the key differences between Struts2 and Spring, two Java web development frameworks.

1. Design goal: Struts2 is an MVC framework that focuses on providing a web application development framework that is easy to develop and maintain. In contrast, Spring is a comprehensive application framework that offers a wider range of functionalities, including dependency injection, AOP, and transaction management.
2. Controller Layer: Struts2 utilizes Actions as controllers, which are responsible for receiving requests and handling business logic. Spring MVC also uses Controllers as controllers, but it is more flexible as it allows the use of annotations to define controllers.
3. Dependency Injection: The Spring framework is known for its powerful dependency injection feature. With dependency injection, developers can decouple different components of an application, improving the code’s testability and maintainability. While Struts2 does not provide a similar dependency injection feature, it can be achieved by integrating with Spring.
4. AOP Support: The Spring framework offers support for aspect-oriented programming (AOP), which allows developers to add extra functionality such as transaction management and logging without modifying the source code. While Struts2 does not directly provide AOP support, it can still be achieved through integration with Spring.
5. Spring framework offers various functional components such as data access, transaction management, security, and remote invocation, while Struts2 focuses mainly on developing web applications by providing web-related functional components like form handling, validation, and file uploading.

Overall, Struts2 and Spring are both popular Java web development frameworks, however, their design goals and functionalities offered are different. The choice of which framework to use depends on the project requirements and the preferences of the development team.