Develop Reference

Extending/modifying generated entities in Hibernate

I am creating a REST api service for a mysql database. I've generated classes using IntelliJ's persistence tool. It does a pretty good job.
There are some quirks to the schema that I am working with. The users want the endpoints to be accessible by another property other than the "id" primary key column.
Ex: /object/<name property>' versus/object/`.
Here is the catch though. The schema can change. The name property is not going anywhere though so I can safely assume that will always be on the object.
I've learned that you can use Superclasses to force these generated entites to have custom properties without affecting the database schema. I dont want to make a model change in the generated entity and have that update the database table layout as it is not my database.
I have a class called Animal.
#Entity
#Table(name = "animals", schema = "xyz123", catalog = "")
public class AnimalEntity extends AnimalSuperclass {
private Integer id;
private String name;
private String description;
#Id
#Column(name = "id", nullable = false)
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
#Basic
#Column(name = "name", nullable = true, length = 80)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#Basic
#Column(name = "description", nullable = true, length = 255)
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
RoleEntity that = (RoleEntity) o;
return Objects.equals(id, that.id) &&
Objects.equals(name, that.name) &&
Objects.equals(description, that.description);
}
#Override
public int hashCode() {
return Objects.hash(id, name, description);
}
}
I have to manually add extends AnimalSuperclass. Which is fine for now. Eventually I am going to try to generate these using .xmls on runtime.
Then I have this superclass..
#MappedSuperclass
public class AnimalSuperclass implements Serializable {
private String testMessage;
private String name;
private Integer id;
#Transient
public String getTestMessage() {
return this.testMessage;
}
public void setTestMessage(String id) {
this.testMessage = testMessage;
}
}
What I want to do is force the #Id annotation to be on the name property from within the superclass. Something like this..
#MappedSuperclass
public class AnimalSuperclass implements Serializable {
private String testMessage;
private String name;
private Integer id;
#Transient
public String getTestMessage() {
return this.testMessage;
}
public void setTestMessage(String id) {
this.testMessage = testMessage;
}
#Basic
#Id
#Column(name = "name", nullable = false, length = 15)
private String getName() {
return name;
}
private void setName(String name) {
this.name = name;
}
#NaturalId
#Column(name = "id", nullable = false)
private Integer getId() {
return id;
}
private void setId(Integer id) {
this.id = id;
}
}
How do I go about doing that? Currently this throws an error when I hit the endpoint: {"cause":null,"message":"Id must be assignable to Serializable!: null"}
Java is not my first language so I am not an expert by any means. But from what I've read, its not possible to override subclass properties from the superclass. Is there a better way to approach this, maybe by using RepositoryRestConfiguration? I am using PagingAndSortingRepository to serve these entities. I cannot extend the entities and use my superclass as a child as that creates a dType property in the schema and I cannot alter the table layout.

There is no hard link between the request and your entity. In your repository you can write methods that can query the data that is brought it from the request.
For example if they are requesting a name you can do something like
Page<AnimalEntity> findByName(String name, Pageable pageable);
in your Repository. Spring will take care of the rest and then you can call this in your controller.
#Service
public class AnimalService {
#Autowired
private AnimalEntityRepository animalRepo;
public Page<AnimalEntity> findAnimal(String name) {
Page<AnimalEntity> animals = animalRepo.findByName(name, new PageRequest(1,20));
return animals;
}
}
One thing to mention is that depending on how you configured Hibernate when sending an entity back to the client and the entity is seralized you might get an failed to lazy initialize error. If that is the case your entities will have to be converted to a POJO (plain old java object) and that sent back.

Getting entity from table without having primary key in Hibernate

I'm currently working on a project where I'm trying to get a list of enities from table which does not have a primary key (dk_systemtherapie_merkmale). This table is 1:n related to another table (dk_systemtherapie). See the screenshot for the table structure.
When getting an entry for dk_systemtherapie, the program fetches the Collection "dkSystemtherapieMerkmalesById". However, the first table entry is fetched as often as the number of actual entries in the table is. It never fetches the other entries from dk_systemtherapie_merkmale. I assume it has something to do with the fact that hibernate can't differ between the entries, but I don't know how to fix it.
Table schema
I've created two corresponding entity classes, dk_systemtherapie:
#Entity
#Table(name = "dk_systemtherapie", schema = "***", catalog = "")
public class DkSystemtherapieEntity {
private int id;
private Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById;
#Id
#Column(name = "id")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
#OneToMany(mappedBy = "dkSystemtherapieByEintragId")
public Collection<DkSystemtherapieMerkmaleEntity> getDkSystemtherapieMerkmalesById() {
return dkSystemtherapieMerkmalesById;
}
public void setDkSystemtherapieMerkmalesById(Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById) {
this.dkSystemtherapieMerkmalesById = dkSystemtherapieMerkmalesById;
}
}
Here the second one, which is accessing the table without a primary key, dk_systhemtherapie_merkmale:
#Entity #IdClass(DkSystemtherapieMerkmaleEntity.class)
#Table(name = "dk_systemtherapie_merkmale", schema = "***", catalog = "")
public class DkSystemtherapieMerkmaleEntity implements Serializable {
#Id private Integer eintragId;
#Id private String feldname;
#Id private String feldwert;
private DkSystemtherapieEntity dkSystemtherapieByEintragId;
#Basic
#Column(name = "eintrag_id")
public Integer getEintragId() {
return eintragId;
}
public void setEintragId(Integer eintragId) {
this.eintragId = eintragId;
}
#Basic
#Column(name = "feldname")
public String getFeldname() {
return feldname;
}
public void setFeldname(String feldname) {
this.feldname = feldname;
}
#Basic
#Column(name = "feldwert")
public String getFeldwert() {
return feldwert;
}
public void setFeldwert(String feldwert) {
this.feldwert = feldwert;
}
#Id
#ManyToOne
#JoinColumn(name = "eintrag_id", referencedColumnName = "id")
public DkSystemtherapieEntity getDkSystemtherapieByEintragId() {
return dkSystemtherapieByEintragId;
}
public void setDkSystemtherapieByEintragId(DkSystemtherapieEntity dkSystemtherapieByEintragId) {
this.dkSystemtherapieByEintragId = dkSystemtherapieByEintragId;
}
}

I assume the problem is releated to the fact that Hibernate is using the following annotation as the one and only id for fetching data from database.
#Id
#ManyToOne
#JoinColumn(name = "eintrag_id", referencedColumnName = "id")
public DkSystemtherapieEntity getDkSystemtherapieByEintragId() {
return dkSystemtherapieByEintragId;
}
This leads to the problem that when getting more than one entry with the same id (as the id is not unique), you will get the number of entries you would like to but hibernate is always fetching the first entry for this id. So in fact you are getting dublicate entries.
So how to fix this?
According to this question: Hibernate and no PK, there are two workarounds which are actually only working when you don't have NULL entries in your table (otherwise the returning object will be NULL as well) and no 1:n relationship. For my understanding, hibernate is not supporting entities on tables without primary key (documentation). To make sure getting the correct results, I would suggest using NativeQuery.
Remove the Annotations and private DkSystemtherapieEntity dkSystemtherapieByEintragId; (incl. beans) from DkSystemtherapieMerkmaleEntity.java und add a constructor.
public class DkSystemtherapieMerkmaleEntity {
private Integer eintragId;
private String feldname;
private String feldwert;
public DkSystemtherapieMerkmaleEntity(Integer eintragId, String feldname, String feldwert) {
this.eintragId = eintragId;
this.feldname = feldname;
this.feldwert = feldwert;
}
public Integer getEintragId() {
return eintragId;
}
public void setEintragId(Integer eintragId) {
this.eintragId = eintragId;
}
public String getFeldname() {
return feldname;
}
public void setFeldname(String feldname) {
this.feldname = feldname;
}
public String getFeldwert() {
return feldwert;
}
public void setFeldwert(String feldwert) {
this.feldwert = feldwert;
}
}
Remove private Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById; (incl. beans) from DkSystemtherapieEntity.java.
Always when you need to get entries for a particular eintrag_id, use the following method instead of the Collection in DkSystemtherapieEntity.java.
public List<DkSystemtherapieMerkmaleEntity> getDkSystemtherapieMerkmaleEntities(int id) {
Transaction tx = session.beginTransaction();
String sql = "SELECT * FROM dk_systemtherapie_merkmale WHERE eintrag_id =:id";
List<Object[]> resultList;
resultList = session.createNativeQuery(sql)
.addScalar("eintrag_id", IntegerType.INSTANCE)
.addScalar("feldname", StringType.INSTANCE)
.addScalar("feldwert", StringType.INSTANCE)
.setParameter("id", id).getResultList();
tx.commit();
List<DkSystemtherapieMerkmaleEntity> merkmale = new ArrayList<>();
for (Object[] o : resultList) {
merkmale.add(new DkSystemtherapieMerkmaleEntity((Integer) o[0], (String) o[1], (String) o[2]));
}
return merkmale;
}
Call getDkSystemtherapieMerkmaleEntities(dkSystemtherapieEntityObject.getid()) instead of getDkSystemtherapieMerkmalesById().

Spring enum exception when a form is submitted

I have User entity and a field Role in this entity. Role is ENUM. I am trying to create user from UI. However, i am getting an exception:
org.springframework.beans.NullValueInNestedPathException: Invalid property 'role' of bean class [com.bionic.entities.User]: Could not instantiate property type [com.bionic.entities.Role] to auto-grow nested property path: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.bionic.entities.Role]: Is it an abstract class?; nested exception is java.lang.InstantiationException: com.bionic.entities.Role
Here is my Role.Enum:
package com.bionic.entities;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import javax.annotation.Resource;
#Resource
public enum Role {
ADMINISTRATOR(1, "administrator"),
TRAINER(2, "trainer"),
STUDENT(3, "student"),
RESTRICTED_ADMINISTRATOR(4, "restricted_administrator"),
RESTRICTED_TRAINER(5, "restricted_trainer");
private long id;
private String name;
Role(){}
private Role(long id, String name) {
this.name = name;
this.id = id;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
My User.class fields:
public class User {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
#Column(name = "first_name", nullable = false)
private String firstName;
#Column(name = "last_name", nullable = false)
private String lastName;
#Column(name = "email", nullable = false, unique = true)
private String email;
#Column(name = "password", nullable = false)
private String password;
#Column(name = "cell")
private String cell;
#Column(name="position")
private String position;
#Enumerated(EnumType.ORDINAL)
#Column(name = "role_id")
private Role role;
and, finally, my html form:
<form method="POST" action="/superAdmin/addUser" th:object="${user}">
<select name="role.id" size="2" th:field="*{role.id}" style="display: block" id="role.id"></select>
<br /> <br /> <input type="submit" value="Upload" class="submit-but">
I've spent 2 days in order to solve that. however, it wasn't successful
How am i creating entity after:
#RequestMapping(value = "/addUser", method = RequestMethod.POST)
public
#ResponseBody
String addUser(#ModelAttribute User user, Model model) {
try {
model.addAttribute("user", user);
superAdministratorService.addUser(user);
return "successful";
} catch (Exception e) {
return "You failed to upload";
}
}

Role has a default package-level constructor and a private constructor with 2 arguments, try to change your package-level constructor to public in order to do that, change
Role(){}
by
public Role(){}
I think this is the cause of your problem. But you cannot set a public constructor in enum, so maybe you must change your implementation to a final class.
UPDATE
public static Role fromId(long id) {
if (1 == id) {
return ADMINISTRATOR;
}
// TODO else if for the rest of enum instances
} else {
throw new AssertionError("Role not know!");
}
}
A possible solution for that would be the following:
Use a DTO (simple POJO with the same properties that the User entity and getters and setters) to receive the object in addUser method, in that DTO define role as integer.
In your enum, create a method like the one above
Create the entity object from de DTO object, using the method above to set the role member in User entity.

Mapping hibernate entity with Jackson annotation

I'm working with Spring, hibernate and MySql but I have some problem with seralization of query result.
First in my entity I added #JsonManagedReference on Set structure (#OneToMany side) and #JsonBackReference on single object reference (#ManyToOne side) and it works but I wasn't be able to retrieve all needed information (for example #ManyToOne reference).
So i swapping #JsonBackReference on set structure and #JsonManagedReference on single object but I retrieve
No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.model.tablesField.TableUI["data"]->java.util.ArrayList[0]->com.domain.Car["carType"]->com.domain.CarType_$$_jvst744_f["handler"])
I tried also with #JsonIgnore on Set structure but it doesn't work for the same issues.
This is my spring configuration
private Properties getHibernateProperties() {
Properties properties = new Properties();
properties.put(PROPERTY_NAME_HIBERNATE_DIALECT, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_DIALECT));
// properties.put(PROPERTY_NAME_HIBERNATE_SHOW_SQL, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_SHOW_SQL));
properties.put(PROPERTY_NAME_HIBERNATE_FORMAT_SQL, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_FORMAT_SQL));
properties.put("hibernate.enable_lazy_load_no_trans",true);
return properties;
and this is part of one of my several entities:
/**
* Car generated by hbm2java
*/
#Entity
#Table(name = "car", catalog = "ATS")
public class Car implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer idCar;
#JsonManagedReference
private CarType carType;
#JsonManagedReference
private Fleet fleet;
private String id;
private int initialKm;
private String carChassis;
private String note;
#JsonBackReference
private Set<Acquisition> acquisitions = new HashSet<Acquisition>(0);
public Car() {
}
public Car(CarType carType, Fleet fleet, int initialKm, String carChassis) {
this.carType = carType;
this.fleet = fleet;
this.initialKm = initialKm;
this.carChassis = carChassis;
}
public Car(CarType carType, Fleet fleet, String id, int initialKm, String carChassis, String note,
Set<Acquisition> acquisitions) {
this.carType = carType;
this.fleet = fleet;
this.id = id;
this.initialKm = initialKm;
this.carChassis = carChassis;
this.note = note;
this.acquisitions = acquisitions;
}
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "id_car", unique = true, nullable = false)
public Integer getIdCar() {
return this.idCar;
}
public void setIdCar(Integer idCar) {
this.idCar = idCar;
}
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "id_carType", nullable = false)
public CarType getCarType() {
return this.carType;
}
public void setCarType(CarType carType) {
this.carType = carType;
}
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "id_fleet", nullable = false)
public Fleet getFleet() {
return this.fleet;
}
public void setFleet(Fleet fleet) {
this.fleet = fleet;
}
#Column(name = "id", length = 5)
public String getId() {
return this.id;
}
public void setId(String id) {
this.id = id;
}
#Column(name = "initialKm", nullable = false)
public int getInitialKm() {
return this.initialKm;
}
public void setInitialKm(int initialKm) {
this.initialKm = initialKm;
}
#Column(name = "carChassis", nullable = false, length = 20)
public String getCarChassis() {
return this.carChassis;
}
public void setCarChassis(String carChassis) {
this.carChassis = carChassis;
}
#Column(name = "note", length = 100)
public String getNote() {
return this.note;
}
public void setNote(String note) {
this.note = note;
}
#OneToMany(fetch = FetchType.LAZY, mappedBy = "car")
public Set<Acquisition> getAcquisitions() {
return this.acquisitions;
}
public void setAcquisitions(Set<Acquisition> acquisitions) {
this.acquisitions = acquisitions;
}
}
one method that uses the query:
#Override
#RequestMapping(value = { "/cars/{idFleet}"}, method = RequestMethod.GET)
public #ResponseBody TableUI getCars(#PathVariable int idFleet) {
TableUI ajaxCall=new TableUI();
try {
ajaxCall.setData(fleetAndCarService.findCarsByIdFleet(idFleet));
return ajaxCall;
} catch (QueryException e) {
ErrorResponse errorResponse= ErrorResponseBuilder.buildErrorResponse(e);
LOG.error("Threw exception in FleetAndCarControllerImpl::addCar :" + errorResponse.getStacktrace());
return ajaxCall;
}
}
two class for the query:
public interface DefRdiRepository extends JpaRepository<DefRdi, Integer>{
//#Query("SELECT CASE WHEN COUNT(c) > 0 THEN true ELSE false END FROM DefRdi c WHERE c.parName = ?1 AND c.description= ?2")
//Boolean existsByParNameAndDescription(String parName, String description);
//Query method of spring, I put findBy and then the key of research
DefRdi findByParNameAndDescription(String parName, String description);
}
public interface CarRepository extends JpaRepository<Car, Integer>, CarRepositoryCustom {
//Query method of spring, I put findBy and then the key of research
List<Car> findByFleetIdFleet(int idFleet);
}
Where is my error? I don't want Set object but only the single reference. The problem is only when I serialize. Thanks
UPDATE:
I use #JSonIgnore on all set collectionts and Eager instead lazy ad all works fine, but is there a way to retrieve all the information only when I want, for example having two different query?
So it doesn't work
#Override
#Transactional
public List<Car> findByFleetIdFleet(int idFleet) {
List<Car> carList= carRepository.findByFleetIdFleet(idFleet);
for (Car car:carList){
Hibernate.initialize(car.getCarType());
Hibernate.initialize(car.getFleet());
}
return carList;
// return carRepository.findByFleetIdFleet(idFleet);
}

All collections need to be fetched eagerly when loading them from data base, in order to get serialized by Spring. Make sure you fetch them eagerly (e.g. FetchMode.JOIN). You could also swap #JsonManagedReference from wanted fields with #JsonIgnore to black listed fields, Spring automatically serialises every field without annotation.
Update:
Changing the data repository to something like that should work, I am not sure it compiles, but I think you will get the point:
#EntityGraph(value = "some.entity.graph", type = EntityGraph.EntityGraphType.FETCH)
#Query(
value = "SELECT c FROM Car c INNER JOIN FETCH c.acquisitions WHERE c.id = :idFleet"
)
public interface CarRepository extends JpaRepository<Car, Integer>, CarRepositoryCustom {
//Query method of spring, I put findBy and then the key of research
List<Car> findByFleetIdFleet(int idFleet);
}
For more information look at this post and read the official documentation.
Workaround:
There seems to be a workaround, however fetching those collections eager like shown above should have a positive performance impact, since there is no need for loading proxies afterwards. Also no open transactions are needed at controller level.

How to Represent Composite keys in Hibernate using Annotations?

So I reverse engineered some tables from my db and when I try to save my object to the db I get the following error:
Initial SessionFactory creation failed.org.hibernate.AnnotationException: A Foreign key refering com.mycode.Block from com.mycode.Account has the wrong number of column. should be 2
Exception in thread "main" java.lang.ExceptionInInitializerError
The Domain objects Are Block which contains a number of Account Objects:
#OneToMany(fetch = FetchType.LAZY, mappedBy = "Block")
public Set<EAccount> getAccounts() {
return this.Accounts;
}
Account has a Composite key of Id and Role. This has been setup in a seperate Class:
#Embeddable
public class BlockAccountId implements java.io.Serializable {
private long blockOid;
private String accountRole;
public BlockAccountId() {
}
public BlockAccountId(long blockOid, String accountRole) {
this.blockOid = blockOid;
this.accountRole = accountRole;
}
#Column(name = "BLOCK_OID", nullable = false)
public long getBlockOid() {
return this.blockOid;
}
public void setBlockOid(long blockOid) {
this.blockOid = blockOid;
}
#Column(name = "ACCOUNT_ROLE", nullable = false, length = 10)
public String getAccountRole() {
return this.accountRole;
}
public void setAccountRole(String accountRole) {
this.accountRole = accountRole;
}
So I want to know. How can I Link the tables Block and account on blockOid but still ensure the account table has both blockOid and accountRole as a composite key.
Any examples would be greatly appreciated!
N.B this is a Block (One) to Account (Many) relationship.
Thanks

The easiest is to place your association directly in the embedded id component.
Hibernate reference documentation
Section 5.1.2.1.1. id as a property using a component type ()
Example (Only write the important getter() and setter())
#Entity
public class Block {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="BLOCK_OID")
long blockOid;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "id.block", cascade=CascadeType.ALL)
Set<Account> accounts = new HashSet<Account>();
}
#Entity
public class Account {
#EmbeddedId BlockAccountId id;
public Account()
{
this.id = new BlockAccountId();
}
public void setBlock(Block pBlock) {
this.id.setBlock(pBlock);
}
public Block getBlock() {
return this.id.getBlock();
}
public String getAccountRole() {
return this.id.getAccountRole();
}
public void setAccountRole(String accountRole) {
this.id.setAccountRole(accountRole);
}
}
#Embeddable
public class BlockAccountId implements java.io.Serializable {
#ManyToOne(optional = false)
private Block block;
#Column(name = "ACCOUNT_ROLE", nullable = false, length = 10)
private String accountRole;
public BlockAccountId() {
}
//Implement equals and hashcode
}
The corresponding database table are :
CREATE TABLE block (
BLOCK_OID bigint(20) NOT NULL auto_increment,
PRIMARY KEY (`BLOCK_OID`)
)
CREATE TABLE account (
ACCOUNT_ROLE varchar(10) NOT NULL,
block_BLOCK_OID bigint(20) NOT NULL,
PRIMARY KEY (`ACCOUNT_ROLE`,`block_BLOCK_OID`),
KEY `FK_block_OID` (`block_BLOCK_OID`),
CONSTRAINT `FK_block_OID` FOREIGN KEY (`block_BLOCK_OID`) REFERENCES `block` (`BLOCK_OID`)
)

based on hibernate documentation here's the link
based on it you can do the following :
#Entity
public class Account {
#EmbeddedId BlockAccountId id;
#MapsId(value = "blockOid")
#ManyToOne
private Block block;
public Account()
{
this.id = new BlockAccountId();
}
public void setBlock(Block pBlock) {
this.block = pBlock;
}
public Block getBlock() {
return this.block;
}
public String getAccountRole() {
return this.id.getAccountRole();
}
public void setAccountRole(String accountRole) {
this.id.setAccountRole(accountRole);
}
}