I am getting nullPointerException from my custom jpa method findShiftNameById() in my shift planner project(github link below). I have used #Query annotation inside ShiftDetailsRepo Interface to implement the method. Please check and let me know what could be causing this. I tried by removing nativeQuery parameter but that gives shift_details not mapped error.I tried by changing datatypes between int and long and also by changing sd.shiftName to sd.shift_name(as per the column name that is available in my actual database) but still same nullPointerException error is coming.
Github link-https://github.com/Anupam5713/shiftPlannerAPI
The method is being called in the ShiftPlanService Class inside the service package
Is there something wrong in my query?
#Query(value = "select sd.shiftName from shift_details sd where sd.shiftId=:shiftId",nativeQuery=true)
public String findShiftNameById(#Param("shiftId") int shiftId);
The following is the cause of NPE. The call to sdr is done before the dependencies are wired.
#Service
public class ShiftPlanService {
#Autowired
ShiftDetailsRepo sdr;
String S1 = sdr.findShiftNameById(1);
String S2 = sdr.findShiftNameById(2);
Move these initializations to a #PostConstruct method.
Example
#PostConstruct
public void initDetails() {
S1 = sdr.findShiftNameById(1);
S2 = sdr.findShiftNameById(2);
}
Related
In Spring Data Jpa to get first 10 rows I can do this findTop10By...(). In my case the number or rows is not defined and comes as a parameter.
Is there something like findTopNBy...(int countOfRowsToGet)?
Here is another way without native query. I added Pageable as a parameter to the method in the interface.
findAllBySomeField(..., Pageable pageable)
I call it like this:
findAllBySomeField(..., PageRequest.of(0, limit)) // get first N rows
findAllBySomeField(..., Pageable.unpaged()) // get all rows
I don't know of a way to do exactly what you want, but if you are open to using #Query in your JPA repository class, then a prepared statement is one alternative:
#Query("SELECT * FROM Entity e ORDER BY e.id LIMIT :limit", nativeQuery=true)
Entity getEntitiesByLimit(#Param("limit") int limit);
Did it by using pagination, as described in the first answer. Just adding a more explicit example.
This example will give you the first 50 records ordered by id.
Repository:
#Repository
public interface MyRepository extends JpaRepository<MyEntity, String> {
Page<MyEntity> findAll(Pageable pageable);
}
Service:
#Service
public class MyDataService {
#Autowired
MyRepository myRepository;
private static final int LIMIT = 50;
public Optional<List<MyEntity>> getAllLimited() {
Page<MyEntity> page = myRepository.findAll(PageRequest.of(0, LIMIT, Sort.by(Sort.Order.asc("id"))));
return Optional.of(page.getContent());
}
}
Found the original idea here:
https://itqna.net/questions/16074/spring-data-jpa-does-not-recognize-sql-limit-command
(which will also link to another SO question btw)
I am working with Spring Data 2.0.6.RELEASE.
I am working about pagination for performance and presentation purposes.
Here about performance I am talking about that if we have a lot of records is better show them through pages
I have the following and works fine:
interface PersonaDataJpaCrudRepository extends PagingAndSortingRepository<Persona, String> {
}
The #Controller works fine with:
#GetMapping(produces=MediaType.TEXT_HTML_VALUE)
public String findAll(Pageable pageable, Model model){
Through Thymeleaf I am able to apply pagination. Therefore until here the goal has been accomplished.
Note: The Persona class is annotated with JPA (#Entity, Id, etc)
Now I am concerned about the following: even when pagination works in Spring Data about the amount the records, what about of the content of each record?.
I mean: let's assume that Persona class contains 20 fields (consider any entity you want for your app), thus for a view based in html where a report only uses 4 fields (id, firstname, lastname, date), thus we have 16 unnecessary fields for each entity in memory
I have tried the following:
interface PersonaDataJpaCrudRepository extends PagingAndSortingRepository<Persona, String> {
#Query("SELECT p.id, id.nombre, id.apellido, id.fecha FROM Persona p")
#Override
Page<Persona> findAll(Pageable pageable);
}
If I do a simple print in the #Controller it fails about the following:
java.lang.ClassCastException:
[Ljava.lang.Object; cannot be cast to com.manuel.jordan.domain.Persona
If I avoid that the view fails with:
Caused by:
org.springframework.expression.spel.SpelEvaluationException:
EL1008E:
Property or field 'id' cannot be found on object of type
'java.lang.Object[]' - maybe not public or not valid?
I have read many posts in SO such as:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to
I understand the answer and I am agree about the Object[] return type because I am working with specific set of fields.
Is mandatory work with the complete set of fields for each entity? Should I simply accept the cost of memory about the 16 fields in this case that never are used? It for each record retrieved?
Is there a solution to work around with a specific set of fields or Object[] with the current API of Spring Data?
Have a look at Spring data Projections. For example, interface-based projections may be used to expose certain attributes through specific getter methods.
Interface:
interface PersonaSubset {
long getId();
String getNombre();
String getApellido();
String getFecha();
}
Repository method:
Page<PersonaSubset> findAll(Pageable pageable);
If you only want to read a specific set of columns you don't need to fetch the whole entity. Create a class containing requested columns - for example:
public class PersonBasicData {
private String firstName;
private String lastName;
public PersonBasicData(String firstName, String lastName) {
this.firstName = fistName;
this.lastName = lastName;
}
// getters and setters if needed
}
Then you can specify query using #Query annotation on repository method using constructor expression like this:
#Query("SELECT NEW some.package.PersonBasicData(p.firstName, p.lastName) FROM Person AS p")
You could also use Criteria API to get it done programatically:
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<PersonBasicData> query = cb.createQuery(PersonBasicData.class);
Root<Person> person = query.from(Person.class);
query.multiselect(person.get("firstName"), person.get("lastName"));
List<PersonBasicData> results = entityManager.createQuery(query).getResultList();
Be aware that instance of PersonBasicData being created just for read purposes - you won't be able to make changes to it and persist those back in your database as the class is not marked as entity and thus your JPA provider will not work with it.
I am using JPA Criteria API with JPA meta model.
final CriteriaBuilder cb = em.getCriteriaBuilder();
final CriteriaQuery<T> criteria = cb.createQuery(User.class);
final Root<T> root = criteria.from(User.class);
criteria.select(root).where(cb.equal(root.get(User_.username), value));
return em.createQuery(criteria).getResultList();
here the problem is root.get method throws NPE first time after the server starts (i.e first execution after server start), but the same code works fine from second execution onwards. It doesn't matter when the first execution executed after server started. It may be executed after few seconds or after few minutes.
Following is the exception thrown:
java.lang.NullPointerException: null
at org.apache.openjpa.persistence.criteria.PathImpl.get(PathImpl.java:245) ~[openjpa-2.4.2.jar:2.4.2]
If you look at the source code of PathImpl.get
public <Y> Path<Y> get(SingularAttribute<? super X, Y> attr) {
if (getType() != attr.getDeclaringType()) {
attr = (SingularAttribute)((ManagedType)getType()).getAttribute(attr.getName());
}
return new PathImpl<X,Y>(this, (Members.SingularAttributeImpl<? super X, Y>)attr, attr.getJavaType());
}
it access attr.getDeclaringType()
If I look at the JPA meta model which is auto generated it looks as follows:
public class User_ {
public static volatile SingularAttribute<User,String> username;
...
}
username is definitely null, however the code works well except first time.
It appears during runtime JPA set value to User_.username.
so question is how do prevent throwing NPE first time!
Using TomEE 7.0.4
Tried to find the answer on the Web but failed. Should be simple for pro Spring Devs... so here it comes:
In few words I want to bind the List of interface type: List to the form and get the data back (possibly modified by user via form. The problem is that it doesn't work :(
my code (short version) - command/model class which is passed to the form:
public class RoomsFormSearchResultCommand extends RoomsFormSearchCommand {
#SuppressWarnings("unchecked")
private List<IRoom> roomsList = LazyList.decorate(new ArrayList<Room>(),
FactoryUtils.instantiateFactory(Room.class));
public List<IRoom> getRoomsList() {
return roomsList;
}
public void setRoomsList(final List<IRoom> roomsList) {
this.roomsList = roomsList;
}
(...)
then in the form I use it like that (short version):
<form:form method="post" action="reserve" commandName="roomsResultsCmd">
(...)
<c:forEach var="room" items="${roomsResultsCmd.roomsList}"
varStatus="status">
<tr>
<td><form:input path="roomsList[${status.index}].roomNumber" readonly="true"/>
(...)
The form is displayed fine but after submitting it I get:
2012-01-22 21:31:55 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [wyspa] in context with path [/wyspa] threw exception [Request processing failed; nested exception is org.springframework.beans.InvalidPropertyException: Invalid property 'roomsList[0]' of bean class [com.wyspa.controller.command.RoomsFormSearchResultCommand]: Illegal attempt to get property 'roomsList' threw exception; nested exception is org.springframework.beans.NullValueInNestedPathException: Invalid property 'roomsList' of bean class [com.wyspa.controller.command.RoomsFormSearchResultCommand]: Could not instantiate property type [com.wyspa.entity.IRoom] to auto-grow nested property path: java.lang.InstantiationException: com.wyspa.entity.IRoom] with root cause
org.springframework.beans.NullValueInNestedPathException: Invalid property 'roomsList' of bean class [com.wyspa.controller.command.RoomsFormSearchResultCommand]: Could not instantiate property type [com.wyspa.entity.IRoom] to auto-grow nested property path: java.lang.InstantiationException: com.wyspa.entity.IRoom
at org.springframework.beans.BeanWrapperImpl.newValue(BeanWrapperImpl.java:633)
at org.springframework.beans.BeanWrapperImpl.growCollectionIfNecessary(BeanWrapperImpl.java:863)
at org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:770)
at org.springframework.beans.BeanWrapperImpl.getNestedBeanWrapper(BeanWrapperImpl.java:555)
(...)
The deal is then when I change the List to "instances" list everything works fine!
public class RoomsFormSearchResultCommand extends RoomsFormSearchCommand {
#SuppressWarnings("unchecked")
//notice that the List is now List<Room>
private List<Room> roomsList = LazyList.decorate(new ArrayList<Room>(),
FactoryUtils.instantiateFactory(Room.class));
In this case data is passed to the controller in proper way.
Since I am used to devlop on interfaces and I am pretty crazy about it I would REALLY prefer not to translate the List<IRoom> (which comes back from services) to List<Room> which seems to suit Spring. Is it possible to work with List<IRoom> in this case or Spring just doesn't support it?
//Of course Room implements IRoom - but I guess you already got that...
I would be VERY happy for any help/suggestions!
Best Regards,
Nirwan
I have exact the same problem. Changing to following won't fix the problem. It looks spring binding ignores the factory utils and tries to instantiate the null object itself:
#SuppressWarnings("unchecked")
private List<IRoom> roomsList = LazyList.decorate(new ArrayList<IRoom>(),
FactoryUtils.instantiateFactory(Room.class));
The workaround is to set auto grow nested path off in your controller:
#InitBinder protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) {
binder.setAutoGrowNestedPaths(false);
super.initBinder(request, binder);
}
The problem is you'll lose the handy nested path like user.account.address.street. You have to make sure none of user, account, addresss is null. It does cause a lot of problems. That's why I came here, see if I can find better solution.
If you don't actually need the list to auto-grow, you can store the form object in the session to avoid the nasty side effects of disabling auto-growing nested paths.
#Controller
#SessionAttributes(types = RoomsFormSearchResultCommand.class)
public final class SearchController {
#InitBinder
protected void initBinder(final WebDataBinder binder) {
binder.setAutoGrowNestedPaths(false);
}
#RequestMapping(method = RequestMethod.GET)
public String showForm(final Model model) {
RoomsFormSearchResultCommand form = ... // create or load form
model.addAttribute(form);
}
#RequestMapping(method = RequestMethod.POST)
public String onSubmitUpdateCart(
#ModelAttribute final RoomsFormSearchResultCommand form,
final BindingResult result,
final SessionStatus status) {
// if result has no errors, just set status to complete
status.setComplete();
}
}
Try the following lines
#SuppressWarnings("unchecked")
private List<IRoom> roomsList = LazyList.decorate(new ArrayList<IRoom>(),
FactoryUtils.instantiateFactory(Room.class));
don't have time to try that myself, but it would make sense.
I am working in J2EE 5 using JPA, I have a working solution but I'm looking to clean up the structure.
I am using EntityListeners on some of the JPA objects I am persisting, the listeners are fairly generic but depend on the beans implementing an interface, this works great if you remember to add the interface.
I have not been able to determine a way to tie the EntityListener and the Interface together so that I would get an exception that lead in the right direction, or even better a compile time error.
#Entity
#EntityListener({CreateByListener.class})
public class Note implements CreatorInterface{
private String message;....
private String creator;
....
}
public interface CreatorInterface{
public void setCreator(String creator);
}
public class CreateByListener {
#PrePersist
public void dataPersist(CreatorInterface data){
SUser user = LoginModule.getUser();
data.setCreator(user.getName());
}
}
This functions exactly the way I want it to, except when a new class is created and it uses the CreateByListener but does not implement the CreatorInterface.
When this happens a class cast exception is thrown somewhere deep from within the JPA engine and only if I happen to remember this symptom can I figure out what went wrong.
I have not been able to figure a way to require the interface or test for the presence of the interface before the listener would be fired.
Any ideas would be appreciated.
#PrePersist
public void dataPersist(Object data){
if (!(data instanceof CreatorInterface)) {
throw new IllegalArgumentException("The class "
+ data.getClass()
+ " should implement CreatorInterface");
}
CreatorInterface creatorInterface = (CreatorInterface) data;
SUser user = LoginModule.getUser();
creatorInterface.setCreator(user.getName());
}
This does basically the same thing as what you're doing, but at least you'll have a more readable error message indicating what's wrong, instead of the ClassCastException.