How to retrieve data from a one to one mapped entity after a filter is applied on to the mapped entity's attribute spring - spring

Question

How to retrieve data from a one to one mapped entity after a filter is applied on to the mapped entity's attribute.
This is my Hotel Entity Class..
package com.springmvcweb.model;
import javax.persistence.*;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
#Entity
#Table(name = "HOTEL", schema = "HOTEL")
public class HotelEntity implements Serializable{
private long hotelId;
private String hotelName;
private String hotelDescription;
private String hotelWebsite;
private Long hotelPhoneNo;
private String hotelEmail;
private Long hotelStarRating;
private AddressEntity addressEntity;
private CategoryEntity categoryEntity;
private List<AmenityEntity> amenitiesList;
#ManyToMany(cascade = {CascadeType.MERGE,CascadeType.PERSIST,CascadeType.DETACH,CascadeType.REFRESH})
#JoinTable(name = "HOTEL_AMENITY", joinColumns = {#JoinColumn(name = "HOTEL_ID", referencedColumnName = "HOTEL_ID")},
inverseJoinColumns = {#JoinColumn(name = "AMENITY_ID", referencedColumnName = "AMENITY_ID")})
public List<AmenityEntity> getAmenitiesList() {
return amenitiesList;
}
public void setAmenitiesList(List<AmenityEntity> amenitiesList) {
this.amenitiesList = amenitiesList;
}
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "HOTEL_ADDRESS_ID")
public AddressEntity getAddressEntity() {
return addressEntity;
}
public void setAddressEntity(AddressEntity addressEntity) {
this.addressEntity = addressEntity;
}
#ManyToOne(cascade = {CascadeType.MERGE,CascadeType.PERSIST,CascadeType.DETACH,CascadeType.REFRESH})
#JoinColumn(name = "HOTEL_CATEGORY_ID")
public CategoryEntity getCategoryEntity() {
return categoryEntity;
}
public void setCategoryEntity(CategoryEntity categoryEntity) {
this.categoryEntity = categoryEntity;
}
#Id
#Column(name = "HOTEL_ID")
public long getHotelId() {
return hotelId;
}
public void setHotelId(long hotelId) {
this.hotelId = hotelId;
}
#Basic
#Column(name = "HOTEL_NAME")
public String getHotelName() {
return hotelName;
}
public void setHotelName(String hotelName) {
this.hotelName = hotelName;
}
#Basic
#Column(name = "HOTEL_DESCRIPTION")
public String getHotelDescription() {
return hotelDescription;
}
public void setHotelDescription(String hotelDescription) {
this.hotelDescription = hotelDescription;
}
#Basic
#Column(name = "HOTEL_WEBSITE")
public String getHotelWebsite() {
return hotelWebsite;
}
public void setHotelWebsite(String hotelWebsite) {
this.hotelWebsite = hotelWebsite;
}
#Basic
#Column(name = "HOTEL_PHONE_NO")
public Long getHotelPhoneNo() {
return hotelPhoneNo;
}
public void setHotelPhoneNo(Long hotelPhoneNo) {
this.hotelPhoneNo = hotelPhoneNo;
}
#Basic
#Column(name = "HOTEL_EMAIL")
public String getHotelEmail() {
return hotelEmail;
}
public void setHotelEmail(String hotelEmail) {
this.hotelEmail = hotelEmail;
}
#Basic
#Column(name = "HOTEL_STAR_RATING")
public Long getHotelStarRating() {
return hotelStarRating;
}
public void setHotelStarRating(Long hotelStarRating) {
this.hotelStarRating = hotelStarRating;
}
public void addAmenities(AmenityEntity amenityEntity){
if(amenitiesList==null){
amenitiesList = new ArrayList<>();
}
amenitiesList.add(amenityEntity);
}
#Override
public String toString() {
return "HotelEntity{" +
"hotelId=" + hotelId +
", hotelName='" + hotelName + '\'' +
", hotelDescription='" + hotelDescription + '\'' +
", hotelWebsite='" + hotelWebsite + '\'' +
", hotelPhoneNo=" + hotelPhoneNo +
", hotelEmail='" + hotelEmail + '\'' +
", hotelStarRating=" + hotelStarRating +
", addressEntity=" + addressEntity +
", categoryEntity=" + categoryEntity +
", amenitiesList=" + amenitiesList +
'}';
}
}
This is AddressEntity Class:
package com.springmvcweb.model;
import javax.persistence.*;
import java.io.Serializable;
#Entity
#Table(name = "ADDRESS", schema = "HOTEL")
public class AddressEntity implements Serializable {
private long addressId;
private String addressLine1;
private String addressLine2;
private String cityName;
private String stateName;
private String countryName;
private Long pincode;
#Id
#Column(name = "ADDRESS_ID")
public long getAddressId() {
return addressId;
}
public void setAddressId(long addressId) {
this.addressId = addressId;
}
#Basic
#Column(name = "ADDRESS_LINE1")
public String getAddressLine1() {
return addressLine1;
}
public void setAddressLine1(String addressLine1) {
this.addressLine1 = addressLine1;
}
#Basic
#Column(name = "ADDRESS_LINE2")
public String getAddressLine2() {
return addressLine2;
}
public void setAddressLine2(String addressLine2) {
this.addressLine2 = addressLine2;
}
#Basic
#Column(name = "CITY_NAME")
public String getCityName() {
return cityName;
}
public void setCityName(String cityName) {
this.cityName = cityName;
}
#Basic
#Column(name = "STATE_NAME")
public String getStateName() {
return stateName;
}
public void setStateName(String stateName) {
this.stateName = stateName;
}
#Basic
#Column(name = "COUNTRY_NAME")
public String getCountryName() {
return countryName;
}
public void setCountryName(String countryName) {
this.countryName = countryName;
}
#Basic
#Column(name = "PINCODE")
public Long getPincode() {
return pincode;
}
public void setPincode(Long pincode) {
this.pincode = pincode;
}
}
Now I want to retrieve all those hotels filtered by their location(say cityname or statename) and I'm using query like this:
#Override
public List<HotelEntity> getHotelsByLocation(String location) {
try{
session = sessionFactory.getCurrentSession();
}catch (Exception e){
session = sessionFactory.openSession();
}
Query query = session.createQuery("from HotelEntity where HotelEntity.addressEntity.cityName " +
"like :location");
query.setParameter("location",location);
return query.getResultList();
}
Also I've used FetchType as EAGER in the HotelEntity OneToOne Mapping like this:
#OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
#JoinColumn(name = "HOTEL_ADDRESS_ID")
public AddressEntity getAddressEntity() {
return addressEntity;
}
Right now it is giving me a null pointer exception. Please guide.

Answer 1

#OneToOne relationship is eagerly fetched anyway so adding that information is redundant.
Regarding the query I would form it like the following:
" select he from HotelEntity he
" inner join he.addressEntity ae"
" where ae.cityName like :location");