I have created a webapp similiar to the tutorial here:
https://spring.io/guides/tutorials/react-and-spring-data-rest/ .
I have added postgresql db and everything works fine. I have a basic query findByUsername(String name) in my repository which works fine. My problem is, I am for some reason unable to create custom queries e.g
"SELECT CURRENT_TIMESTAMP".
Lets say i make a test where I just want to get the value of this statement. And by unable I mean I don't know how :)
My google results suggested my to add this to my class
#Autowired
EntityManager entityManager;
and then create queries on that. But entityManager is never initialized for some reason, return null always. Is this the right way and I'm just missing something? Also tried to add spring-boot-starter-jdbc and use JdbcTemplate but was also null.
EDIT
My problem was too little knowledge of Spring.
I had a class like this and tried to use Autowire in there.
public class Person {
#Autowire
MyRepo myRepo;
private String p;
public Person(String p) {
this.p = p;
}
As I understood later, Spring doesn't pick this up. I called out this class in a RestController with Person per = new Person("string");.
The solution I made was to Autowire MyRepo in my RestController class and my Person contstructor looked like this
public Person(String p, MyRepo myRepo) {
this.p = p;
this.myRepo = myRepo;
}
Removed the autowire in Person class. This way I managed to get myRepo initialized in Person class and use it there. This isn't the best soution for my problem.
My second problem. After i got this working, I tried to autowire EntityManager the same to my Person class. Just replaced MyRepo with EntityManager and it was also initialized. Now the problem is with my next code line Integer i = (Integer) em.createNativeQuery("select 1", Integer.class).getSingleResult();. Here I get an error javax.persistence.PersistenceException: org.hibernate.MappingException: Unknown entity: java.lang.Integer.
The purpose of this statement is to make a simple query to my DB, to if it responds.
You don't need to autowire the EntityManager, Spring takes care of all this for you.
Instead in your repository you need to define a new method and annotate it with #Query.
Example:
#Query(value = "select current_timestamp from #{#entityName} u")
String findTimestamp();
You can find furhter information about using #Query in the spring docs: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.at-query.
The final solution was:
Integer i = (Integer) em.createNativeQuery("select 1").getSingleResult();
Just removed the Integer.class part from NatviveQuert. I guess, if I had wanted it to be there, I should have made a new bean for Integer.
Overall this is not the best practice in Spring but it solved my problem.
Related
When repository.save(t) is called from my service, which is in turn called from my controller, all works just fine, and the object is inserted into the database table; But, when the service is called from my test class, Hibernate returns the created object but does not really flush the transaction into the database. I have tried using #Transactinal and #Commit in my test class and also on my #Test methods, but no difference in the result. I have also tried other solutions which involve using org.springframework.test.context.transaction.TestTransaction class, but any method call on this class throws an exception.
this is my super class for test:
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
public abstract class QaApplicationTest {
protected abstract void initializeTest() throws Exception;
protected abstract void cleanupTestEffects() throws Exception;
}
And this is my concrete test class:
public class RequestControllerTest extends QaApplicationTest {
#Autowired
private SiteService siteService;
#Autowired
private RequestService requestService;
#Test
#Transactional
public void givenObject_whenInsertToDB_thenCreated() throws Exception{
Site siteObject = siteService.save(siteObject); //Here I need a commit.
Request request = new Request(site.getId());
Request savedRequest = requestService.save(request); //Here database returns "Parent Key Not Found" error.
Assertions.assertTrue(savedRequest.getId()>0);
}
}
I know the #Transactional on test methods are used to roll back all the changes made inside the method, however, In my case, the changes are not even committed in the first place. And I have used #org.springframework.transaction.annotation.Transactional which is the correct annotation. I don't know which part I am doing wrong! Any idea?
My colleague found the issue; we had used a third-party library (Camunda) that had enabled batch-insert on Hibernate. So by disabling the batch operation the issue was resolved and the insert is actually taking place now. Not sure, why we faced this only in Spring Test and not in the main application though. if anyone has a comment, we appreciate it.
I would like to use the Spring Data Projection technique in order to extract from a table only some fields (and not all fields of the table).
As described in the documentation (https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections) I created a simple interface, for example:
interface NamesOnly {
String getFirstname();
String getLastname();
}
But I have some problems to use it.
Problem 1:
First of all, I would like to use the name findAll() to create a query that finds all rows with only two fields (firstName and lastName):
#Repository
public interface PersonaRepository extends JpaRepository<Persona, Long> {
List<NamesOnly> findAll();
}
But in this case I have these errors (maybe because findAll() is a method of the JpaRepository):
implements org.springframework.data.jpa.repository.JpaRepository.findAll
The return type is incompatible with JpaRepository.findAll()
Problem 2:
Ok, so I try to change the name of the method to findAllOnlyNames():
#Repository
public interface PersonaRepository extends JpaRepository<Persona, Long> {
List<NamesOnly> findAllOnlyNames();
}
But now I have this error:
Caused by:
org.springframework.data.mapping.PropertyReferenceException: No
property findAllOnlyNames found for type Persona!
Because Spring tries to create a query from the name.
1) Could it be possible to reuse the method name findAll() without having problems with JpaRepository?
2) Could it be possible to turn off the query creation from the method name (only for some queries, not for all projects or repositories)?
You are on the right track, your findAll() is in conflict with the ones specified on the existing Spring Data interfaces and you can rename it (as you tried) but it still has to be a name that is compatible with the query derivation mechanism. Try this instead:
#Repository
public interface PersonaRepository extends JpaRepository<Persona, Long> {
List<NamesOnly> findAllOnlyNamesBy();
}
This part of the Spring Data JPA documentation explains how the query creation process works:
The mechanism strips the prefixes find…By, read…By, query…By, count…By, and get…By from the method and starts parsing the rest of it.
So you just need to add the By keyword in the method name, anything after that keyword is treated as a condition, in this case there is no condition so it fetches everything.
To disable the query derivation from the method name you would need to add an #Query(...) annotation to the method and specify either a JPA or native query instead.
You can specify an explicit query rather than rely on it being derived from the method name.
#Repository
public interface PersonaRepository extends JpaRepository<Persona, Long> {
#Query("select p from Persona p")
List<NamesOnly> findAllOnlyNames();
}
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.at-query
Overriding findAll() (even in the unlikely event it is possible) is probably a bad idea.
Another question appeared during my migration from an E3 application to a pure E4.
I got a Structure using inheritance as in the following pic.
There I have an invocation sequence going from the AbstractRootEditor to the FormRootEditor to the SashCompositeSubView to the TableSubView.
There I want to use my EMenuService, but it is null due to it can´t be injected.
The AbstractRootEditor is the only class connected to the Application Model (as a MPart created out of an MPartDescriptor).
I´d like to inject the EMenuService anyway in the AbstractSubView, otherwise I would´ve the need to carry the Service through all of my classes. But I don´t have an IEclipseContext there, due to my AbstractSubView is not connected with Application Model (Do I ?).
I there any chance to get the service injected in the AvstractSubView?
EDIT:
I noticed that injecting this in my AbstractSubView isn´t possible (?), so I´m trying to get it into my TableSubView.
After gregs comment i want to show some code:
in the AbstractRootEditor:
#PostConstruct
public final void createPartControl(Composite parent, #Active MPart mPart) {
...
ContextInjectionFactory.make(TableSubView.class, mPart.getContext());
First I got an Exception, saying that my TableSubView.class got an invalid constructor, so now the Constructor there is:
public TableSubView() {
this.tableInputController=null;
}
as well as my Field-Injection:
#Inject EMenuService eMenuService
This is kind of not working, eMenuService is still null
If you create your objects using ContextInjectionFactory they will be injected. Use:
MyClass myClass = ContextInjectionFactory.make(MyClass.class, context);
where context is an IEclipseContext (so you have to do this for every class starting from one that is injected by Eclipse).
There is also a seconds version of ContextInjectionFactory.make which lets you provide two contexts the second one being a temporary context which can contain additional values.
Looking at this answer, it says:
If you don't want to use an Application Client Container and instead just run the application client class through a java command, injection won't be possible and you'll have to perform a JNDI lookup.
However, given that I am trying to inject a DAO bean like the example shown here, if I cannot do the automatic injecting, it means my application must manually do the JNDI lookup and all the transaction begin/end that I would get for free if the #EJB actually worked.
However, since everything is all within the same Eclipse EJB Project (it also failed with the same null handle when I had my client code in a Dynamic Web Project), surely there must be an easy way to get it all working? Can anyone suggest what I am doing wrong?
Finally, this article suggests that DAOs are not needed, but if I replace within my EJB:
#EJB MyDao dao;
with the more direct:
#PersistenceContext private EntityManager em;
I still get the similar null value; is this the same injection failure problem?
NB: I have just noticed this answer:
This is a bug in Glassfish (apparently in the web services stack).
I am running v4.0 Build 89, which still has this bug? Does this mean I have to do all JPA actions the long-winded way?
I eventually found out that the problem/issue is that in order to use injection of the #PersistenceContext the class MUST be a bean itself. This is hinted at in the example on Wikipedia:
#Stateless
public class CustomerService {
#PersistenceContext
private EntityManager entityManager;
public void addCustomer(Customer customer) {
entityManager.persist(customer);
}
}
I could delete this question, but perhaps leaving this answer might provide a hint to someone, or at least show them a minimal working example of EJB and JPA.
I have a java EE project using JPA (transaction-type="JTA"), hibernate as provider. I write my beans to handle the CRUD things. The program running in JBOSS 7 AS.
I have an EntityManagerDAO :
#Stateful
public class EntityManagerDao implements Serializable {
#PersistenceContext(unitName = "dtdJpa")
private EntityManager entityManager;
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public Object updateObject(Object object) {
object = entityManager.merge(object);
return object;
}
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public void createObject(Object object) {
entityManager.persist(object);
}
public void refresh(Object object) {
entityManager.refresh(object);
}
public <T> T find(Class<T> clazz, Long id) {
return entityManager.find(clazz, id);
}
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public void deleteObject(Object object) {
entityManager.remove(object);
}
}
but when I invoke deleteObject, this exception comes out.
java.lang.IllegalArgumentException: Removing a detached instance com.test.User#5
How is this caused and how can I solve it?
EntityManager#remove() works only on entities which are managed in the current transaction/context. In your case, you're retrieving the entity in an earlier transaction, storing it in the HTTP session and then attempting to remove it in a different transaction/context. This just won't work.
You need to check if the entity is managed by EntityManager#contains() and if not, then make it managed it EntityManager#merge().
Basically, the delete() method of your business service class should look like this:
em.remove(em.contains(entity) ? entity : em.merge(entity));
In my case, I got the same error, when I tried to delete an object
using,
session.delete(obj)
without creating any transaction before that.
And the problem is solved by creating the transaction first(session.beginTransaction() and then deleting the object.
I hope my answer will help someone :)
Sometimes its simply because you are missing the #Transaction annotation for add, remove, update operations.
I faced the same problem. The detached entity should be re-attached. As #BalusC mentioned, using EntityManager.merge() should be used to attach the detached entity. EntityManager.merge() generates SQL Query which fetches the current state of the entity, on which EntityManager.remove() has to be performed. But in my case it didn't worked.
Try EntityManager.remove(EntityManager.find(Class<T>,arg)) instead. It worked for me.
In my experience, if I query an object from the DB then closed the entity manager then do a DB delete, the problem happens. Or if I copy that loaded object to another instance then do a delete, this problem also happens.
In my opinion there are 2 things to keep note:
The object must be in the same session that was created by the Entity Manager
And the object mustn't be transferred to another object while the Entity Manager's session is still opened.
Cheers