PhoneContoller

PhoneController.java

package com.spring.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.spring.demo.model.Phone;
import com.spring.demo.service.PhoneService;

@Controller
public class PhoneController {

    private PhoneService phoneService;

    @Autowired(required = true)
    @Qualifier(value = "phoneService")
    public void setPhoneService(PhoneService ps) {
        this.phoneService = ps;
    }

    @RequestMapping(value = "/phones", method = RequestMethod.GET)
    public String listPhones(Model model) {
        model.addAttribute("phone", new Phone());
        model.addAttribute("listPhones", this.phoneService.listPhones());
        return "phone";
    }

    // For add and update phone both
    @RequestMapping(value = "/phone/add", method = RequestMethod.POST)
    public String addPhone(@ModelAttribute("phone") Phone p) {

        if (p.getId() == 0) {
            // new phone, add it
            this.phoneService.addPhone(p);
        } else {
            // existing phone, call update
            this.phoneService.updatePhone(p);
        }

        return "redirect:/phones";

    }

    @RequestMapping("/remove/{id}")
    public String removePhone(@PathVariable("id") int id) {

        this.phoneService.removePhone(id);
        return "redirect:/phones";
    }

    @RequestMapping("/edit/{id}")
    public String editPhone(@PathVariable("id") int id, Model model) {
        model.addAttribute("phone", this.phoneService.getPhoneById(id));
        model.addAttribute("listPhones", this.phoneService.listPhones());
        return "phone";
    }

}
`

@ModelAttribute:

• This annotation is used for preparing the model data and also to define the command object that would be bound with the HTTP request data.
• This annotation can be applied on the methods as well as on the method arguments.
• In the above controller example, we used it on the argument of the addPhone() method.

An @ModelAttribute on a method argument indicates the argument should be retrieved from the model. If not present in the model, the argument should be instantiated first and then added to the model. Once present in the model, the argument's fields should be populated from all request parameters that have matching names. This is known as data binding in Spring MVC, a very useful mechanism that saves you from having to parse each form field individually.

@PathVariable:

It binds the method parameter to a URI template variable. URI template is a parameterized URI