How to convert the data from MongoDB to the View through the Controller in Spring MVC

Question

In Application.java, I have read each document in a collection from a MongoDB database. And I stored all these documents in an ArrayList. I am wondering how to pass this ArrayList to the Controller class?

This is a Spring Boot web application. And I am using Spring MVC to work on this project.

This class is the Application.java. I fetched all the shoes from MongoDB and stored them in the list variable.

public class Application implements CommandLineRunner {

    @Autowired
    private ShoeRepository repository;
    public static void main(String[] args) {

        SpringApplication.run(Application.class, args);
    }
    @Override
    public void run(String... args) throws Exception {

        // fetch all shoes
        List<Shoe> list = new ArrayList<>();
        System.out.println("Shoes found with findAll():");
        System.out.println("-------------------------------");
        for (Shoe shoe : repository.findAll()) {
            //System.out.println(customer);
            list.add(shoe);
        }
        System.out.println("all shoes have been saved to the list");
    }
}

This class is my Controller class:

---

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import java.util.List;

@Controller
public class GreetingController {

    @RequestMapping(value = "/greeting" ,method = RequestMethod.GET)
    public String greeting(@RequestParam(name="name", required=true) List<Shoe> list, Model model) {
        model.addAttribute("name", list.get(0).asin);
        return "greeting";
    }
}

Who can tell me how to pass the list variable in the Application class to the Controller class? I want to visualize the data stored in the list variable in the View.

Answer 1

You are missing the main point here. A controller class is different from a main application class in spring-boot. The controller class is used to serve the http request according to the path. Each request is served by a different thread. The springboot follows the MVC architecture for this.So, you should have a Controller class to serve the request , a Service class to create the model and a Repository layer to access the database whichever it may be. And also the Model class is returned from the controller.

@Controller
public class GreetingController {

    @Autowired
    private ShoeRepository repository;

    @RequestMapping(value = "/greeting" ,method = RequestMethod.GET)
    public String greeting(@RequestParam(name="name", required=true) List<Shoe> list, Model model) {
        model.addAttribute("name", list.get(0).asin);
        List<Shoe> list = new ArrayList<>();
        list.addAll(repository.findAll());
        return "greeting";
    }
}

You could call the repository method from the controller to access the data which should be the right way to go ,or better yet , have a service class in between if you have more logic to be implemented.

public interface ShoeRepository extends MongoRepository<Shoe, Long> {

    //Custom Query
    @Query("SELECT o FROM Object o WHERE o.field = somethingThatValidsIt")
    public List<Shoe> customFindAll();

    //Default CRUD repository implementation
    public List<Shoe> findAll()

    //Other methods
    public Shoe findByNameAndAvailable(String name, boolean available);

}