I am working on a Jhipster app Java service and Angular 5 UI. I have an entity working fine, but I need to get a list of one of the fields (customer) from that entity to display in the UI.
In this case it's a single table I am using which contains the client name, so I am trying to get a distinct list returned for read only.
I have tried creating a custom repository and added a function into the service, Impl class and resource class.
Upon startup its failing with cannot find a property getClientNameList on the entity.
I have show a snippet of the code from the Entity class, the custom repository and the method I added into the PostsServiceImpl class.
Can someone please steer me in the right direction?
Thanks.
// Entity Class //
#Entity
#Table(name = "posts")
public class Posts implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name="client_name")
private String clientName;
// Other fields here
...
}
// Custom Repository //
#Repository
public interface JobsRepositoryCustom {
List<String> getClientNameList();
}
// PostsServiceImpl //
public class PostsServiceImpl implements PostsService {
EntityManager entityManager;
public List<String> getClientNameList() {
Query query = entityManager.createNativeQuery("SELECT clientName FROM Posts", Posts.class);
return query.getResultList();
}
}
Your error might be more specifically that clientName is not found. It is not found because if you run a native query you need to use the database column names.
So change:
"SELECT clientName FROM Posts"
to
"SELECT client_name FROM Posts"
Related
there is already a similar post. Since this is already older, I hope something has changed since then (How does the FetchMode work in Spring Data JPA)
I would like to run all jpa repository#findById in one select, if the relationship is marked with EAGER. However, spring data ignores the EAGER specification and the FETCH.JOIN annotation from hibernate.
Is there a generic solution that all findById queries are executed in one select?
I wouldn't want to write a separate JPL or EntityGraph for each query. Does anyone know a generic solution?
JpaReposistory
The easiest option would be to write a JpaRepository<T, Id>. This is still a custom repository. However, you do not have to write so much code. You mainly have to write a repository interface for each relevant class and annotate the findById(Long id) method with a graph. The advantage is that if you edit your entity, the repository method will not need any changes because you define the entity graph within the entity class itself.
#Entity
#NamedEntityGraph(name = "Department.detail",
attributeNodes = #NamedAttributeNode("employees"))
public class Department {
#Id
#GeneratedValue
private Long id;
private String name;
#OneToMany(fetch = FetchType.LAZY)
private List<Employee> employees;
// ...
}
public interface DepartmentRepository extends JpaRepository<Department, Long> {
#EntityGraph(value = "Department.detail", type = EntityGraphType.LOAD)
List<Department> findById(Long id);
}
As Spring data ignores the #Fetch(Fetchmode.JOIN) annotation or the information fetch = FetchType.EAGER, you cannot influence the join how you want it to be within the entity itself.
JPQL Query Where You Need It
Another option can be considered as a bad software engineering style: You can call the database queries directly where you need them. This means that you execute the code which you would usually write in the repository.
public ClassWithQueryResults {
#PersistenceContext
private EntityManager entityManager;
public void methodWhereYouNeedYourResults() {
TypedQuery<Department> query = entityManager.createQuery(
"SELECT DISTINCT d FROM Department d LEFT JOIN d.employees e",
Department.class);
List<Department> departments = query.getResultList();
// ...
}
}
Repository With JPQL, Generics and Reflection
Taking the previously suggested idea, you can create a custom repository which is valid for all your entities. The first step would be to create an attribute in your entity class in which you store the attribute which should be fetched.
public class Department extends AbstractEntity {
public static void String ATTRIBUTE_TO_FETCH = "employees";
...
}
With some tweaking, this can be extended to an array/list of all the fields which should be fetched. As this attribute is directly in your entity classes, the chance for any mistakes and future effort is low. Obviously, this attribute should have the same name in all your entities.
The next step would be to create the repository. I provide an example with the findAll() method. You have to pass it only the class name of the entities you want to have and the generics and reflection do the rest. (Consider what you want to do with the exceptions.)
public <T> List<T> findAll(Class<T> tClass)
throws NoSuchFieldException, IllegalAccessException {
String className = tClass.getSimpleName();
String attributeToFetch = (String)
tClass.getDeclaredField("ATTRIBUTE_TO_FETCH").get(null);
String queryString = String.format("SELECT DISTINCT p FROM %s p LEFT JOIN p.%s c",
className, attributeToFetch);
TypedQuery<T> query = entityManager.createQuery(queryString, tClass);
return query.getResultList();
}
Depending on how you want to implement this, the modification/generation of a query through simple manipulation of a String can offer the possibility of SQL injection attacks.
I'm trying to implement inheritance with Kotlin and JPA. My abstract base class (annotated with #Entity) holds the ID (annotated with #Id and #GeneratedValue) and other metadata, like createDate, etc. I'm getting several errors from Hibernate, one for each field except the ID:
org.hibernate.tuple.entity.PojoEntityTuplizer - HHH000112: Getters of lazy classes cannot be final: com.example.BaseEntity.createDate
As I've read I need to include the open keyword for each property.
I have 3 questions regarding this:
Why do I have to do that in the superclass, and don't need in subclass? I'm not overriding those properties.
Why isn't it complaining about the ID?
It seems to work without the open keyword, then why is the error logged?
Edit:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
abstract class BaseEntity(
#Id #GeneratedValue(strategy = GenerationType.IDENTITY) val id: Long = 0,
val createdAt: Instant = Instant.now()
)
#Entity
class SubClass(
val someProperty: String = ""
) : BaseEntity()
I'm using the JPA plugin for Gradle, which I believe creates the noarg constructor, that's why I don't have to specify everything nullable.
Thank you!
The logged error has to do with lazy loading.
Hibernate extends entities at runtime to enable it. It is done by intercepting an access to properties when an entity is loaded lazily.
Kotlin has flipped the rules and all classes are final by default there. It is the reason why we're advised to add an open keyword.
If a property is not open hibernate cannot intercept access to it because final methods cannot be overridden. Hence the error.
Why isn't it complaining about the ID?
Because #Id is always loaded. There is no need to intercept access to it.
It seems to work without the open keyword, then why is the error logged?
The key word here is seems. It may introduce subtle bugs.
Consider the following #Entity:
#Entity
public class Book {
#Id
private Long id;
private String title;
public final Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public final String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
And the #Test:
#Test
public void test() {
EntityManager entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
// signal here
Book book = new Book();
book.setId(1L);
book.setTitle("myTitle");
entityManager.persist(book);
// noise
entityManager.getTransaction().commit();
entityManager.close();
entityManager = entityManagerFactory.createEntityManager();
entityManager.getTransaction().begin();
// signal
Book reference = entityManager.getReference(Book.class, 1L);
String title = reference.getTitle();
assertNull(title); // passes
entityManager.getTransaction().commit();
entityManager.close();
}
This test passes but it should not (and fails if getTitle is not final).
This would be hard to notice
Why do I have to do that in the superclass, and don't need in subclass? I'm not overriding those properties.
Looks like Hibernate gives up when it sees final #Entity.
Add open to SubClass and you will the precious:
2019-05-02 23:27:27.500 ERROR 5609 --- [ main] o.h.tuple.entity.PojoEntityTuplizer : HHH000112: Getters of lazy classes cannot be final: com.caco3.hibernateanswer.SubClass.someProperty
See also:
final methods on entity silently breaks lazy proxy loading
How to avoid initializing HibernateProxy when invoking toString() on it? - my old question (note that Hibernate uses Byte Buddy these days).
PS
Did you forget to include #MappedSuperclass on BaseEntity?
Without the annotation it should fail with something like:
org.hibernate.AnnotationException: No identifier specified for entity: com.caco3.hibernateanswer.SubClass
I have the following working without FetchType.LAZY:
#Entity
public class Test {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String text;
#ManyToOne
#JoinColumn(name = "lazy_id")
private Lazy lazy;
//getters and setters
}
#Entity
public class Lazy {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String text;
//getters and setters
}
And the query method:
public List<Test> all() {
try {
return em.createQuery("FROM Test t").getResultList();
} catch (NoResultException e) {
return null;
}
}
This is the JSON result:
[{"id":1,"text":"test 1","lazy":{"id":1,"text":"lazy 1"}},
{"id":2,"text":"test 2","lazy":{"id":2,"text":"lazy 2"}}]
However I want to return just the id and text data, so I tried to change the #ManyToOne(fetch = FetchType.LAZY)
Then I get this errors:
Severe: Generating incomplete JSON
Severe: org.hibernate.LazyInitializationException: could not initialize proxy [model.Lazy#1] - no Session
I could do something like changing the query to fetch only the fields I want:
public List<Test> all() {
try {
return em.createQuery("SELECT t.id, t.text FROM Test t").getResultList();
} catch (NoResultException e) {
return null;
}
}
But then my response in the JavaScript front end is:
[[1,"test 1"],[2,"test 2"]]
Not a array of objects anymore, mapping everything giving the amount of entities I have is far from ideal.
Most of the content I found is how to fetch the data afterwards, which is not my concern, all I need is to send only fields I want in the first place. I`m not sure whether the EJB #TransactionAttribute should be used or not, I couldn't find a working example. I also tried to change the strategy to a #OneToMany in the Lazy class but to no avail.
Since your question dates back a bit, I hope it's still relevant for you:
If you declare a mapping as lazy (or it is like that by the default behaviour), JPA won't fetch it until it is accessed. So your Lazy class will only be accessed if JSON tries to convert the whole thing and at that point it seems that you no longer have an open session, so the data can't be fetched and will result in an org.hibernate.LazyInitializationException.
If you stick with a lazy mapping (which is in general mostly fine), you have to explicitely fetch or access it, if you need the data for an use case.
Check out Vlad's excellent explanation on the topic.
Login
#ApiModel
#Entity
public class Login {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
private LocalDateTime loginDateTime;
/** Other fields ***/
}
LoginDateOnly
interface LoginDateOnly {
#Value("#{target.loginDateTime.toLocalDate()}")
LocalDate getDateFromLoginDateTime();
}
LoginRepository
#RepositoryRestResource(collectionResourceRel = "login", path = "login")
public interface LoginRepository extends PagingAndSortingRepository<Login, Long> {
Collection<LoginDateOnly> findAll();
/** Other query methods **/
}
I simply want to get all my Login record, with LocalDate part of my loginDateTime selected/projected using a http://host/api/login. But currently I'm encountering a clash with CrudRepository's findAll(). How to solve this as much as possible using projection. I'm making #Query and #NamedQuery my last resort.
A findAll method signature is:
List<T> findAll();
If you want to override it you cannot use another signature.
All you need to get a list of your projections is define another method for this, for example:
Collection<LoginDateOnly> findAllBy();
But as I can see you are using the Spring Data REST, so in this case you don't need to define a new method. You should firstly add annotation #Projection to your projection:
#Projection(name = "loginDateOnly", types = Login.class)
interface LoginDateOnly {
//...
}
Then use its name in the request url:
GET http://host/api/login?projection=loginDateOnly
See more info in the doc: Projections and Excerpts
I am using Spring Boot to implement rest api. There are three entities SeqTb, PairTb, and GroupTb and they are nested. SeqTb has manytoone with PairTb. PairTb has onetomany relationship with SeqTb and also manytoone with GroupTb.
//SeqTb.java
#Entity
#Table(name="SEQ_TB")
public class SeqTb implements Serializable {
.......
#ManyToOne
#JoinColumn(name="PAIR_ID")
private PairTb pairTb;
......
}
// PairTb.java
#Entity
#Table(name="PAIR_TB")
#NamedQuery(name="PairTb.findAll", query="SELECT p FROM PairTb p")
public class PairTb implements Serializable {
#ManyToOne
#JoinColumn(name="GROUP_ID")
private GroupTb groupTb;
#OneToMany(mappedBy="pairTb", cascade=CascadeType.ALL)
private List<SeqTb> seqTbs;
}
//GroupId.java
#Entity
#Table(name="GROUP_TB")
public class GroupTb implements Serializable {
//bi-directional many-to-one association to PairTb
#OneToMany(mappedBy="groupTb", cascade=CascadeType.ALL)
private List<PairTb> pairTbs;
}
In my controller GET request with analysisId was handled in the following way:
#RequestMapping(
value = "/api/seqs/{analysis_id}",
method = RequestMethod.GET,
produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<SeqTb> getSeqByAnalysisId(#PathVariable("analysis_id") String analysis_id) {
SeqTb seq = seqService.findByAnalysisId(analysis_id);
return new ResponseEntity(seq, HttpStatus.OK);
}
I also create a bean class SeqServiceBean that extends the interface SeqService which in turn calls methods from the following JPA repository for query.
//SeqRepository.java
#Repository
public interface SeqRepository extends JpaRepository<SeqTb, Integer> {
#Override
public List<SeqTb> findAll();
public List<SeqTb> findByAnalysisId(String analysisId);
}
When I query a SeqTb object with SeqTb.PairTb == null, the api works just fine. However, if the analysisId I put in the url belongs to a SeqTb record that associates with a pairId which in turn belongs to a groupId, the program would go nuts. Below is the output, the first part output is correct (bold text). After that it keeps printing PairTb and GroupTb in loops (repeating keywords pairTb, groupTb).
{"rowId":8,"analysisId":"cce8d2c2-a6dc-4ee9-ba97-768f058abb50","analyteCode":"D","center":"UCSC",
"pairTb":{"rowId":4,"pairCode":"01ad975d-c2ed-4e4d-bd3b-c9512fc9073c","groupTb":{"rowId":1,"groupName":"PAWG_pilot-50","pairTbs":[{"rowId":1,"pairCode":"00ad0ffe-2105-4829-a495-1c2aceb5bb31","groupTb":{"rowId":1,"groupName":"PAWG_pilot-50","pairTbs":
Meanwhile I got lots of errors from tomcat server:
Caused by: java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:565) ~[tomcat-embed-core-8.0.32.jar:8.0.32]
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:212) ~[tomcat-embed-core-8.0.32.jar:8.0.32]
How do I ignore the nested entity object inside an entity and get only the meaning columns?
You can also annotate a property with #JsonIgnore in order to not output that field.
Found the solution. Created a value object that only contains the specific columns from entity and leave out the nested entity object. And it works.