Let me tell you why I’m writing about this. For years, I’ve watched teams stare at massive, aging enterprise applications built with Apache Struts. The code works. The business depends on it. But everyone knows it’s running on an architectural foundation that feels increasingly isolated from the modern world of cloud, containers, and microservices. The question is never if to modernize, but how without inviting disaster. That’s where a thoughtful integration with Spring Boot comes in.
Think of it this way: you have a large, complex machine that does its job well. You don’t want to smash it and build a new one from scratch. That’s too risky and expensive. Instead, you want to give it a new, more powerful core and better internal systems, while keeping the outer shell operational. Spring Boot can become that new core for your Struts application.
This approach is about building a bridge, not a wall. It lets you preserve the substantial investment in your application’s user interface and business workflows. At the same time, it opens the door to the tools and practices that define current development. You get to move forward without starting over.
How does this work in practice? The key is to let Spring Boot take control of the application’s lifecycle and dependency management. You configure your Struts actions as beans within the Spring application context. This means Spring creates them, wires them up, and manages their dependencies.
Here’s a basic look. First, you set up a standard Spring Boot application. Then, you configure a Struts action to be managed by Spring.
// A Struts Action, now defined as a Spring Component
@Component
@Scope(value = "request")
public class LegacyUserAction extends Action {
// Spring can now inject services directly
@Autowired
private ModernUserService userService;
@Override
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
// Business logic using the modern Spring-managed service
List<User> users = userService.findAll();
request.setAttribute("userList", users);
return mapping.findForward("success");
}
}Notice what happened? The LegacyUserAction is still a Struts class. It handles the request and forward just like before. But now, the ModernUserService it uses is provided by Spring. This is a small, safe change with a big impact: your old Struts code can immediately use new, properly engineered Spring services.
What about the configuration? You need to bootstrap Struts within the Spring Boot world. This involves creating a custom listener.
// A listener to initialize Struts within Spring Boot
public class SpringStrutsBridgeListener extends StrutsListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
// Get the Spring ApplicationContext
WebApplicationContext context = WebApplicationContextUtils.
getRequiredWebApplicationContext(sce.getServletContext());
// Set it for Struts to find
sce.getServletContext().setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, context);
super.contextInitialized(sce);
}
}You then register this listener in your application.properties or main class. This piece of glue code is the handshake between the two frameworks. It ensures Struts can look into the Spring context to find its actions.
Now, consider the immediate benefits. Suddenly, your legacy application can use Spring’s transaction management. Its security can be reinforced with Spring Security. You can add health checks, metrics, and externalized configuration via Spring Boot Actuator. New REST APIs can be built with Spring MVC right alongside the old Struts pages, sharing the same service layer.
But you must be mindful. You are managing two frameworks that both want to handle web requests. A clear strategy is non-negotiable. A common rule is to let Struts own the existing, stable pages and workflows. All new functionality, especially APIs, should be built directly with Spring MVC. This creates a natural boundary and a clear path for the future.
What about testing? This is where the integration truly shines. Because your Struts actions are Spring beans, you can write focused unit tests for them without starting a web server. You can inject mock services and test the action logic in isolation—something notoriously difficult with classic Struts.
@SpringBootTest
public class LegacyUserActionTest {
@Autowired
private LegacyUserAction action;
@MockBean
private ModernUserService userService;
@Test
public void testExecute() {
// Configure mock and test the action logic
when(userService.findAll()).thenReturn(Arrays.asList(new User("John")));
// ... simulate request and test forward logic
}
}Is this a permanent solution? Not ideally. It’s a strategic transition state. The goal is to gradually box in the Struts functionality. Over time, as pages need major revisions, you re-implement them as modern Spring MVC controllers. The shared Spring-managed service layer makes this migration page-by-page, or module-by-module, perfectly feasible.
This path respects the reality of enterprise systems. It acknowledges the value of what exists while providing a safe, incremental route to a more sustainable architecture. You reduce risk, deliver modern features faster, and keep the business running smoothly.
Have you faced a monolithic legacy system that feels too big to change? The fear of breaking something critical is real. This integration strategy is about replacing that fear with a plan. It turns an overwhelming problem into a series of manageable, low-risk steps.
If you’re looking at a vast Struts application and wondering how to start its journey to the modern age, consider letting Spring Boot shoulder the heavy lifting. Start with the services, then the configuration, then the web layer. You might be surprised how quickly you can bring new life to old code.
I hope this look at a practical modernization path has been helpful. Have you tried a similar approach? What challenges did you face? Share your thoughts in the comments below—let’s learn from each other’s experiences. If this guide can help a teammate, please pass it along.
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