Spring - Failed to convert property value of type java.lang.String to required type - spring

Question

I am making a project of the Housing Association in Spring.
When I'm trying to add an object to my list of apartments I'm getting an error that is written somehow on the page:
https://s28.postimg.org/vrhy6mbd9/blad.jpg
Apartments have relation Many to One Building.
Apartment Controller:
package pl.dmcs.spoldzielnia.controllers;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.ServletRequestUtils;
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 org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.servlet.ModelAndView;
import pl.dmcs.spoldzielnia.domain.Apartment;
import pl.dmcs.spoldzielnia.service.ApartmentService;
import pl.dmcs.spoldzielnia.service.BuildingService;
#Controller
#SessionAttributes
public class ApartmentController {
#Autowired
ApartmentService apartmentService;
#Autowired
BuildingService buildingService;
#RequestMapping("admin/apartment")
public String listApartment(Map<String, Object> map, HttpServletRequest request) {
int apartmentId = ServletRequestUtils.getIntParameter(request, "apartmentId" , -1);
if (apartmentId > 0)
{
Apartment apartment = apartmentService.getApartment(apartmentId);
apartment.setBuilding(buildingService.getBuilding(apartmentService.getApartment(apartmentId).getBuilding().getId()));
map.put("selectedBuilding", apartmentService.getApartment(apartmentId).getBuilding().getId());
map.put("apartment", apartment);
}
else
map.put("apartment", new Apartment());
map.put("buildingList", buildingService.listBuilding());
map.put("apartmentList", apartmentService.listApartment());
return "apartment";
}
#RequestMapping(value = "admin/addApartment", method = RequestMethod.POST)
public String addContact(#ModelAttribute("apartment") Apartment apartment, BindingResult result,
HttpServletRequest request, Map<String, Object> map) {
if (result.getErrorCount()==0)
{
if (apartment.getId()==0)
{
if (apartment.getBuilding().getId() > 0)
apartment.setBuilding(buildingService.getBuilding(apartment.getBuilding().getId()));
apartmentService.addApartment(apartment);
}
else
{
apartmentService.editApartment(apartment);
}
return "redirect:/admin/apartment.html";
}
map.put("buildingList", buildingService.listBuilding());
map.put("apartmentList", apartmentService.listApartment());
return "apartment";
}
#RequestMapping("admin/delete/apartment/{apartmentId}")
public String deleteApartment(#PathVariable("apartmentId") Integer apartmentId) {
apartmentService.removeApartment(apartmentId);
return "redirect:/admin/apartment.html";
}
// #RequestMapping("/apartment")
// public ModelAndView showContacts() {
//
// return new ModelAndView("apartment", "command", new Apartment());
// }
Domain:
package pl.dmcs.spoldzielnia.domain;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
#Entity
#Table(name="apartment")
public class Apartment {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
int id;
#Column(name="apartmentNumber", nullable=false)
private String number;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
#ManyToOne
private Building building;
public Building getBuilding() {
return building;
}
public void setBuilding(Building building) {
this.building = building;
}
}
}
Building Service Implementation:
package pl.dmcs.spoldzielnia.service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import pl.dmcs.spoldzielnia.dao.BuildingDAO;
import pl.dmcs.spoldzielnia.domain.Building;
import pl.dmcs.spoldzielnia.domain.Building;
#Service
#Transactional
public class BuildingServiceImpl implements BuildingService{
#Autowired
BuildingDAO buildingDAO;
#Transactional
public void addBuilding(Building building) {
buildingDAO.addBuilding(building);
}
#Transactional
public List<Building> listBuilding() {
return buildingDAO.listBuilding();
}
#Transactional
public Building getBuilding(int id) {
return buildingDAO.getBuilding(id);
}
#Transactional
public void removeBuilding(int id) {
buildingDAO.removeBuilding(id);
}
#Transactional
public void editBuilding(Building building) {
buildingDAO.editBuilding(building);
}
}
Could you help me to solve my problem?

Answer 1

The problem is that you are assuming that Spring MVC is going to be able to fill your Apartment object from the data passed. From the form it looks like the Building number is 12, which probably is a unique identifier for the Building in the database, but how is Spring MVC going to know how to go to the database, retrieve the proper building object and put it into the Apartment object?
Remember that objects mapped through SpringMVC parameters are regular Java POJOs, not Hibernate attached entities. So, when the mapping occurs SpringMVC is trying to put "12" into the building attribute of type Building into your POJO (which explains the error you are getting).
You have two options:
First, you can register a custom formatter, that will use the passed id to retrieve a Building from the database:
import org.springframework.core.convert.converter.Converter;
public class BuildingIdToBuildingConverter implements Converter<String, Building> {
private BuildingService buildingService;
public BuildingIdToBuildingConverter(BuildingService buildingService) {
this.buildingService = buildingService;
}
#Override
public Building convert (String id) {
return buildingService.getBuilding(id);
}
}
And register it:
public class AppConfig extends WebMvcConfigurerAdapter {
...
#Bean
public BuildingService buildingService(){
return new BuildingService();
}
#Override
public void addFormatters (FormatterRegistry registry) {
registry.addConverter(new BuildingIdToBuildingConverter(buildingService()));
}
}
Second, do this work manually by sending the building id in a separate parameter:
#RequestMapping(value = "admin/addApartment", method = RequestMethod.POST)
public String addContact(#ModelAttribute("apartment") Apartment apartment, #RequestParam("buildingId") String buildingId, BindingResult result, HttpServletRequest request, Map<String, Object> map) {
if (result.getErrorCount()==0){
if (apartment.getId()==0){
apartment.setBuilding(buildingService.getBuilding(buildingId));
apartmentService.addApartment(apartment);
}
}
else{
apartmentService.editApartment(apartment);
}
return "redirect:/admin/apartment.html";
}
map.put("buildingList", buildingService.listBuilding());
map.put("apartmentList", apartmentService.listApartment());
return "apartment";
}
And change your HTML accordingly to send the buildingId value.