Develop Reference

How to get non related entity using JPA

I have two entities
#Entity
public class Language {
#Id
#GeneratedValue
private int id;
private String name;
private String isoCode;
}
and the another entity
#Entity
public class MainEntity {
#Id
#GeneratedValue
private int id;
private String anotherField;
private Language language; //(here I want to return the full entity)
}
The entities don't have a database relation just a string field, Now I want to do a query for MainEntity but I want to get the full entity
For example
Language
value
id
1
name
English
isoCode
EN
MainEntity
value
id
a
name
xyz
language
EN
I have that repository
public interface MainRepository extends JpaRepository<MainEntity, Integer>{
User findAll();
}
but I want that when I do a search on my primary entity it brings me the entire language entity
for example
MyEntity.Language.getName()

Use native query to read JPA objects? See this simplified example where you can use any valid native sql query syntax.
You could put Language getLanguage() function to MainEntity class.
String sql = "Select * From MyEntityTable Where id between (?1 and ?2)";
Query query = entityMgr.createNativeQuery(sql, MyEntity.class);
query.setParameter(1, 1001);
query.setParameter(2, 2002);
List<MyEntity> list = query.getResultList();

If you don't want to make a reletion between MainEntity and Language you have to make a native query. (As is you can't make also a jpql query because you should have at least the String language in the MainEntity in order to make a join on String isoCode in Language but as I understand I think you don't want to do that).
So you have to perform a native query returning an interface as stated here
public interface IntermediateObject {
int getId();
String getName();
int getLanguageId();
String getLanguageName();
String getIsoCode();
}
In the repository:
#Query("select m.id as id, m.name as name, l.id as languageId, l.name as languageName, l.isoCode as isoCode MainEntity m join Language l on m.language = l.isoCode", native=true)
List<IntermediateObject> someMethod();
In the MainEntity or better another dto you have to declare a constructor:
public class AnotherDto {
private int id;
private String name;
private LanguageDto language;
public AnotherDto(int id, String name, int languageId, String languageName, String isoCOde) {
this.id = id;
this.name = name;
this.language = new LanguageDto(languageId, languageName, isoCode);
}
}
public class LanguageDto {
private int id;
private String name;
private String isoCode;
public LanguageDto(int id, String name, String isoCode) {
this.id;
this.name = name;
this.isoCode = isoCode;
}
}
And in the service layer you have to construct AnotherDto from IntermediateObject
public List<AnotherDto> someMethod() {
return repository.someMethod().stream().map(i -> new AnotherDto(i.getId(), i.getName(), i.getLanguageId(), i.getLanguageName(), i.getIsoCode())).collect(Collectors.toList());
}
and now you have the language object populated.
Anyway I suggest to map the entities instead to do all of this.

returning a list of instances by the foreign key

I have two models, Owner and Contract. A contract has an instance of an owner, owner does not have a list of contracts. I'm trying to query my list of contracts, to return a list filtered by owner, ie, a list of contracts by owner.
I had tried to follow previous examples and use Criteria to write a custom query, but, following suggestions I've checked the docks and tried to use named queries instead, however, I'm still really struggling.
There was an unexpected error (type=Internal Server Error, status=500).
Named parameter not bound : ownerId; nested exception is org.hibernate.QueryException: Named parameter not bound : ownerId
My models look like this:
#Entity
#Table(name="Contracts")
#NamedQueries({
#NamedQuery(
name = "Contract.allContractsByOwner",
query = "SELECT c FROM Contract c WHERE c.owner.id LIKE :ownerId"
)
})
public class Contract {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column
private Long id;
#ManyToOne
private Owner owner;
#Column
private double price;
#Column
private String deliverDate;
public Contract(Owner owner, double price, String deliverDate) {
this.id = id;
this.owner = owner;
this.price = price;
this.deliverDate = deliverDate;
}
and
#Entity
#Table(name="Owners")
public class Owner {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column
private Long id;
#Column
private String name;
public Owner(String name){
this.name = name;
}
my contractRepoImpl
#Service
public class ContractRepositoryImpl implements ContractRepositoryCustom {
ContractRepository contractRepository;
#Autowired
EntityManager entityManager;
public List allContractsByOwner(Long ownerId) {
List contracts = entityManager.createQuery(
"SELECT c FROM Contract c WHERE c.owner.id LIKE :ownerId", Contract.class)
.getResultList();
return contracts;
}
}
which I name in my ContractRepo and ContractRepoCustom files, and then in my controller I map to it like so. But, when I query it in my browser I get the error in my terminal.
#GetMapping(value="/owners/{ownerId}/contracts")
public List allContractsByOwner(#PathVariable("ownerId") Long ownerId){
return contractRepository.allContractsByOwner(ownerId);
}
I appreciate this is probably beginners mistakes, I am trying to follow docs but get a bit stuck with syntax & where annotations need to go.

Thanks JB Nizet, got there in the end
I added parameters to my contractRepoImpl
#Service
public class ContractRepositoryImpl implements ContractRepositoryCustom {
ContractRepository contractRepository;
#Autowired
EntityManager entityManager;
public List allContractsByOwner(Long id) {
List contracts = entityManager.createQuery(
"SELECT c FROM Contract c WHERE c.owner.id = :ownerId", Contract.class)
.setParameter("ownerId", id)
.getResultList();
return contracts;
}
}
that then produced a SQL error, which I fixed by changing my #NamedQuery from 'LIKE' to '=' in my Contract class...
#NamedQueries({
#NamedQuery(
name = "Contract.allContractsByOwner",
query = "SELECT c FROM Contract c WHERE c.owner.id = :ownerId"
)
})

JPA - How to query using Specification and #EmbeddedId?

I'm using a JPA query that uses a specification to retrieve entities. When I execute the query, I'm getting the error:
org.springframework.data.mapping.PropertyReferenceException: No property name found for type Task!
I've looked at the answers to similar questions that have been asked on this site previously & tried to model my code to follow the patterns that were recommended but the code is still failing.
When I step through the code with a debugger, the expanded path in the criteria builder is returning the embedded ID class, but when the specification is actually used in the query it looks like the attribute is being applied to the base entity class.
Am I missing something obvious?
Here is the entity class:
#Entity
#Table(name = "TASKS")
public class Task implements Serializable {
#EmbeddedId
private TaskId id;
...more attributes, getters and setters
}
Here is the embedded ID entity class:
#Embeddable
public class TaskId implements Serializable {
#Column(name = "NAME", length = 100)
private String name;
...more attributes, getters and setters
}
Here is the specification builder that matches on the embedded id 'name' attribute:
public class HasTaskNameSpec {
private HasTaskNameSpec() {
}
public static Specification<Task> equals(String name) {
return (root, query, criteriaBuilder) -> {
return criteriaBuilder.equal(root.get("id").get("name"), taskName);
};
}
}
The query is executed on the repository as follows:
List<Task> results = taskRepository.findAll(HasTaskNameSpec.equals("foo"));
The repository itself is very simple:
public interface TaskRepository extends JpaRepository<Task, TaskId>, JpaSpecificationExecutor<Task> {
List<Task> findByIdName(String name);
Page<Task> findByIdName(String name, Pageable page);
}
** EDIT added methods to repository as was suggested below **

Ahh, the root cause was totally in our codebase. There was a sort order being specified on the page that didn't include the embedded "id" attribute. The above code works.

'root.get({embeddedIdName}).get({subPropertyName})' is used to query on embeddedId using specification.
#Embeddable
public class ProjectId implements Serializable{
private static final long serialVersionUID = 1L;
#Column(name = "PROJECT_NAME")
private String projectName;
#Column(name = "ORGANIZATION")
private String organization;
......
......
}
#Entity
#Table(name = "projects")
public class Project {
#EmbeddedId
private ProjectId projectId;
#Column(name = "STARTED_TIME")
private Timestamp startedTime;
#Column(name = "ACTIVE")
private String active;
#Column(name = "DESCRIPTION")
private String description;
......
......
}
In the above snippet, ProjectId is an embedded id. To query on projectName, we should use below snippet.
expression = root.get("projectId").get("projectName");
Demo application link.

Take a look at this link which has a similar query.
EmbbededId Lookup
The final answer suggests that you can add a method to your TaskRepository thus.
public interface TaskRepository extends JpaRepository<Task, TaskId>, JpaSpecificationExecutor<Task> {
public List<Task> findByIdName(String name);
}

Hibernate query for multiple associations

I have the following structure in JAVA.
public class Article {
private long id;
private Source source;
}
public class Source {
private long id;
private Type type;
}
public class Type {
private long id;
private String sourceType;
}
How do I query all articles with Type.id = somevalue using Hibernate Criteria. Right now I can only query until Source class like this
Criteria query = currentSession().createCriteria(Article.class)
.createAlias("source", "s")
.add(Restrictions.eq("s.id", Long.parseLong(typeId)));

Try this
Criteria query = currentSession().createCriteria(Article.class)
.createAlias("source", "s")
.createAlias("s.type","t")
.add(Restrictions.eq("t.id", Long.parseLong(typeId)));

Spring Data Mongo - How to query by #DBRef field's id

I am new to Spring Data Mongo so I must be doing something wrong because I can't manage to execute such a simple query. This is my model:
#Document(collection="brands")
public class Brand{
#Id
private int id;
private String name;
...
//getters-setters
}
#Document(collection="models")
public class Model{
#Id
private int id;
private String name;
#DBRef
private Brand brand;
...
//getters-setters
}
I would like to get all models from a brand, so I implement the DAO as follows:
#Repository
public interface IModelDAO extends MongoRepository<Model, Integer>{
#Query(value="{ 'brand.$id' : ?0 }")
public List<Model> findByBrandId(Integer id);
}
If I execute this mongodb query in the shell it works: db.modelss.find({ 'brand.$id' : 1 })
But, the Java application throws the following exception:
Caused by: java.lang.IllegalAccessError
at org.springframework.data.mapping.PropertyReferenceException.detectPotentialMatches(PropertyReferenceException.java:134)
Apparently it is looking for a field $id in Brand class, and since it doesn't exist it fails. So I change the query to the following, so that it navigates to the id field:
#Query(value="{ 'brand.id' : ?0 }")
Now, it doesn't throw an exception but it doesn't find anything in the DB.
Debugging the MongoTemplate.executeFindMultiInternal() method in can see that in
DBCursor cursor = null;
try {
cursor = collectionCallback.doInCollection(getAndPrepareCollection(getDb(), collectionName));
cursor's query is query={ "brand" : 134}. So it makes sense it doesn't find anything. Changing the query value during debugging to query={ "brand.$id" : 134} it works.
So, why isn't the query correctly translated?

The problem was caused by the #Id int type. Changing it to Integer solved it:
#Document(collection="brands")
public class Brand{
#Id
private Integer id;
private String name;
...
//getters-setters
}
#Document(collection="models")
public class Model{
#Id
private Integer id;
private String name;
#DBRef
private Brand brand;
...
//getters-setters
}

try this;
Query que = new Query();
que.addCriteria(Criteria.where("user.$id").is(new ObjectId("123456789012345678901234")));