Java EE Questions - Part 3

• The `Model` interface (e.g., `org.springframework.ui.Model`).
• `ModelMap` or `ModelAndView` objects.
• Any Java object (POJOs, DTOs, or entities) that holds data, not strictly limited to JavaBeans.

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class UserController {
    @GetMapping("/user")
    public String getUser(Model model) {
        model.addAttribute("username", "John Doe");
        model.addAttribute("user", new User("John", "john@example.com"));
        return "userView"; // Logical view name
    }
}
                

• In Struts (especially Struts 1), the Model was typically implemented using JavaBeans, which are simple Java classes following conventions (e.g., private fields with public getters and setters).
• The Model encapsulated business logic and state, often interacting with services or data access layers.
• Form Beans (e.g., `ActionForm`) were used to capture and validate user input, tightly coupled to the framework.

• Spring MVC is more flexible and does not mandate JavaBeans. The Model can be any Java object (POJO, DTO, or entity) passed to the View via the `Model` interface or `ModelAndView`.
• Spring supports automatic data binding from HTTP requests to objects (e.g., using `@ModelAttribute`), reducing the need for specialized form beans like in Struts.
• Business logic is typically handled by services or other components, not directly in the Model objects, promoting better separation of concerns.
• Spring MVC integrates seamlessly with other Spring modules (e.g., Spring Data, Spring Security), allowing the Model to include entities from ORMs like Hibernate.

• POJOs: Plain Java objects with getters and setters.
• DTOs: Data Transfer Objects for specific use cases.
• Entities: Objects mapped to a database via JPA/Hibernate.
• Maps or Collections: For simple or dynamic data.

public class User {
    private String name;
    private String email;
    // Getters and setters
    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }
}

@Controller
public class UserController {
    @PostMapping("/saveUser")
    public String saveUser(@ModelAttribute User user, Model model) {
        model.addAttribute("savedUser", user);
        return "resultView";
    }
}