Spring MVC

@Controller
class MyController {

  @RequestMapping("/")
  public String home() {
    return "index";
  }
}

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
class HomeController {

  @GetMapping("/")
  public String home() {
    return "index";
  }

  @GetMapping("/hello")
  @ResponseBody
  public String hello() {
    return "Hello from Spring MVC";
  }
}

// Output:
// /hello -> Hello from Spring MVC

• 1 A web framework in Spring.
• 2 Follows Model-View-Controller pattern.
• 3 Used for web applications.
• 4 Supports both REST and UI apps.

• 1 Model – data layer.
• 2 View – UI layer.
• 3 Controller – request handler.

• 1 Client sends request.
• 2 Controller processes request.
• 3 Model prepares data.
• 4 View renders response.

• 1 Clean separation of concerns.
• 2 Easy maintainability.
• 3 Scalable architecture.
• 4 Flexible web development.

• 1 Used in web applications.
• 2 Used in enterprise Java systems.
• 3 Used in form-based applications.
• 4 Used in traditional server-side rendering apps.
• 5 SaaS products use Spring MVC in services, dashboards, background jobs, and API workflows.
• 6 ERP and banking systems apply Spring MVC with validation, logging, review, and rollback plans.
• 7 E-commerce and healthcare platforms use Spring MVC carefully because reliability and data correctness matter.

• 1 A Java program first evaluates the surrounding context, then applies the Spring MVC rules to the current data.
• 2 The important mental model is input, transformation, result, and failure path.
• 3 In production, the same flow usually sits inside a larger layer such as a controller, service, repository, job, or UI component.

• 1 Choose the simplest implementation first, then measure real workloads.
• 2 Watch for repeated work inside loops, unnecessary allocations, and slow I/O in hot paths.
• 3 Prefer clear data structures and stable APIs before micro-optimizing syntax.

• 1 Treat external input as untrusted until it is validated.
• 2 Avoid hardcoded secrets and never print sensitive values in examples or logs.
• 3 Use established libraries for authentication, encryption, parsing, and database access.

• 1 Mixing business logic in controller.
• 2 Not using service layer.
• 3 Confusing @Controller and @RestController.
• 4 Improper view mapping.
• 5 Skipping the small working example before adding framework code.
• 6 Ignoring null, empty, duplicate, and boundary inputs.
• 7 Mixing business logic, input handling, and output formatting in one place.
• 8 Using broad error handling that hides the real failure.
• 9 Forgetting to test the behavior after refactoring.
• 10 Adding clever code that future maintainers will struggle to read.

• 1 Separate Controller, Service, and Model layers.
• 2 Use @RestController for APIs.
• 3 Keep controllers thin.
• 4 Use proper view resolvers.
• 5 Start with clear requirements and one minimal working example.
• 6 Use meaningful names that explain business intent.
• 7 Keep examples small enough to debug line by line.
• 8 Validate input at every trust boundary.
• 9 Handle errors explicitly and preserve useful context.
• 10 Prefer simple control flow over deeply nested logic.
• 11 Separate domain logic from I/O and framework code.
• 12 Write tests for normal, boundary, and failure cases.
• 13 Review security assumptions before production use.
• 14 Measure performance before optimizing.
• 15 Document non-obvious decisions close to the code or in project notes.
• 16 Use official documentation when behavior is version-specific.
• 17 Keep dependencies current and remove unused code.
• 18 Avoid hardcoded secrets, credentials, and environment-specific paths.
• 19 Log operational events without exposing sensitive data.
• 20 Design examples so learners can safely modify and rerun them.

• 1 Beginner: rewrite the example with different names and values.
• 2 Intermediate: add validation and handle one expected failure case.
• 3 Advanced: place Spring MVC inside a small service-style design with tests.

• 1 Build a small Java console feature that demonstrates Spring MVC.
• 2 Accept input, process it with the concept, print a clear result, and handle invalid input.
• 3 Add a README note explaining the design choice and two edge cases you tested.

• 1 If the program does not compile, check spelling, imports, braces, and file/class names first.
• 2 If output is unexpected, print intermediate values and verify each branch of the logic.
• 3 If the design feels complex, reduce it to the smallest working example and add pieces back one at a time.

• 1 Practice Spring MVC with a second example from a business domain such as inventory, payroll, banking, or e-commerce.
• 2 Review related Java topics that cover data flow, error handling, testing, and clean design.
• 3 Compare your solution with official documentation and simplify anything you cannot explain clearly.