I'm beginner in java programming. And I try to write simple stand alone application with spring data. To basic example which is here http://spring.io/guides/gs/accessing-data-jpa/ I want to add, auditing mechanism which will store previous values for objects. I want in customer entity, on #PreUpdate store old values in another table, but I do not know how.
#Entity
#EntityListeners(AuditingEntityListener.class)
public class Customer implements Serializable {
...
#Transient
private transient Customer savedState;
#PreUpdate
public void onPreUpdate() {
if (!savedState.firstName.equals(this.firstName)) {
log.info(String.format("first name was modified, new value =%s, old value=%s",this.firstName, savedState.firstName ));
}
}
#PostLoad
private void saveState(){
this.savedState = (Customer) SerializationUtils.clone(this); // from apache commons-lang
}
Related
im working in a spring boot project and i have a requirement to save the old object in a specific table before each new save ; this my man entities:
#Entity
#Table(name="demande")
public class Demande {
#Id
private Long id;
// all properties
}
#Entity
#Table(name="demande_log")
public class DemandeLog {
#Id
private Long id;
// all properties
}
what im trying to do is before each demandeRepository.save(demande);
i want to save the old demande object (current row in database) as DemandeLog in my demande_log table.
do you have any idea how using spring data, i know that there is a listener #PrePersist in JPA.. but i want to do it properly.
Regards.
I recommend using Envers. It is easy to set up and gives you a complete change log.
I am creating a simple spring application which is supposed to book seats in a seminar. Lets say Booking class looks like this
#Entity
#Table(name = "bookings")
#IdClass(BookingId.class)
public class Booking{
#Id
private Long seminarId;
#Id
private String seatNo;
// .. other fields like perticipant info
// .. getter setters
}
of course the BookingId class:
public class BookingId implements Serializable{
private static final long serialVersionUID = 1L;
private Long seminarId;
private String seatNo;
// .. constructors, getters, setters
}
And I have a repository
#Repository
public interface BookingsRepository extends JpaRepository<Booking, BookingId>{
}
in the controller when a booking request arrives I first check if a booking with same seminer id and seat number already exists, if it doesn't exist I create one
#RequestMapping(method = RequestMethod.POST)
public ResponseEntity<BaseCrudResponse> createNewBooking(#Valid #RequestBody NewBookingDao newBookingDao, BindingResult bindingResult){
logger.debug("Request for a new booking");
// .. some other stuffs
Booking newBooking = new Booking();
newBooking.setSeminarId(newBookingDao.getSeminarId());
newBooking.setSeatNumber(newBookingDao.getSeatNumber());
// .. set other fields
Booking existing = bookingsRepository.findOne(new BookingId(newBooking.getSeminarId(), newBooking.getSeatNumber());
if (existing == null)
bookingsRepository.save(newBooking);
return new ResponseEntity<>(new BaseCrudResponse(0), HttpStatus.CREATED);
}
return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);
}
Now what will happen if the save method of the repository didn't finish commiting transaction and another request already gets past the existence check ? There might be incorrect booking (the last commit will override the previous). Is this scenario likely to happen ? Will the repository ensures that it completes the transaction before another save call ?
Also is there any way to tell Jpa to throw some exception (for IntegrityConstraintException if the composite key (in this case seminerId and seatNumber) already exists ? Now in the present setting its just updating the row.
You can use javax.persistence.LockModeType.PESSIMISTIC_WRITE so other transactions except the one that got the lock cannot update the entity.
If you use spring-data > 1.6 you can annotate the repository method with #Lock :
interface BookingsRepository extends Repository<Booking, Long> {
#Lock(LockModeType.PESSIMISTIC_WRITE)
Booking findOne(Long id);
}
For sure you need to handle the locking exception that may be thron in the controller.
I have two entities, Books and Comments, in a one to many relationship (one book can have many comments). I want to be able to list books and number of comments about a book. I want it denormalized, meaning the books entity will have a counter that has number of comments for that book, and it will be updated every time a comment is entered (just playing with the concept, no need to discuss about the need of denormalizing here).
I think (correct me if I am wrong) this could be easily done with a trigger in the database (whenever a new comment is created, update a counter in the books table to the corresponding bookId), but for the sake of learning I want to do it through JPA, if it makes sense.
What I have so far: //omitted some annotations, just general info
Boks entity:
#Entity
public class Books {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String title;
private String author;
private Long numComments;
// getters and setters...
}
Comments entity:
#Entity
public class Comments {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String comment;
private Long authorId;
private Long bookId;
// getters and setters...
}
Books repository: I added here a query to perform the update
/**
* Spring Data JPA repository for the Books entity.
*/
public interface BooksRepository extends JpaRepository<Books,Long> {
#Modifying
#Query("UPDATE Books v SET v.numComments = v.numComments + 1 WHERE v.id = :bookId")
int updateCounter(#Param("bookId")Long bookId);
}
And now the question: What next? I think I can put the update of the Books entity annotating with #PostPersist a method of the entity Comments, but I have been unsuccessful so far. I can imagine something like this:
#PostPersist //This function in the entity Comments
protected void updateBooks() {
//Likely some call to the repository here that updates the count
// in books the info we have from current entity.
}
Any idea on how to do this? Some best practices about this kind of denormalization in JPA? Better to use the database triggers?
spring not managed your entity classes and your idea is possible but you must inject BooksRepository in enttiy class then stay at you get Nullpointerexception because spring not managed enttiy classes,The reason your BooksRepository not initlaized, try also read this post Bean injection inside a JPA #Entity and anotate entity class #Configurable after
try this
#PostPersist
protected void updateBooks(Comments comment) {
int totalComment = BooksRepository.updateCounter(comment.getBookId());
System.out.println(totalComment); // see totalComment in console
}
but good aprroach in service classes after call updateCounter when insert comment
example in your CommendService : when try a insert commend after call your updateCounter
if(comment.getBookId() != null) //Simple Control
{
CommentRepository.save(comment);
BooksRepository.updateCounter(comment.getBookId());
}
I am using Spring Data JPA in a Spring Boot Application, with MYSQL. There I am saving a list of entities with unique constraint over a field. Out of the list of entities, there is one entity that will throw DataIntegrityViolationException due to the unique constraint. I noticed that none of the entities get persisted in that case, even those that does not violate the unique constraint.
What should be the ideal approach in this case so that those entities which do not violate the unique get persisted ?
Of course I can iterate the list and save them one by one. In fact that is what SimpleJpaRepository is doing underneath.
#Transactional
public <S extends T> List<S> save(Iterable<S> entities) {
List<S> result = new ArrayList<S>();
if (entities == null) {
return result;
}
for (S entity : entities) {
result.add(save(entity));
}
return result;
}
My code - Entity :
#Entity
#Table(uniqueConstraints = #UniqueConstraint(columnNames = { "name" }, name = "uq_name"))
public class SampleContent {
#Id
#GeneratedValue
private Long id;
private String name;
//getter setters
}
Repository :
public interface SampleContentRepository extends JpaRepository<SampleContent, Serializable>{
}
JUnit test :
#Test
public void testCreate(){
List<SampleContent> sampleContentList = new ArrayList<>();
SampleContent sampleContent1 = new SampleContent();
sampleContent1.setName("dd");
SampleContent sampleContent2 = new SampleContent();
sampleContent2.setName("Roy");
SampleContent sampleContent3 = new SampleContent();
sampleContent3.setName("xx");
sampleContentList.add(sampleContent1);
sampleContentList.add(sampleContent2);
sampleContentList.add(sampleContent3);
try{
this.sampleContentRepository.save(sampleContentList);
}catch(DataIntegrityViolationException e){
System.err.println("constraint violation!");
}
}
There is an entity with name "Roy" already present in the table. So, the entire transaction fails and #Transactional rolls back.
I think you can use next steps:
Load existing entities from DB into Set
Override equals and hashCode methods based on name
call Set::addAll you antities (or just add them one by one)
save that Set to DB
Maybe it's suboptimal because forces you to make select * query. But I think it's much more effective then saving entities one by one to DB.
Accotding to this article you can use name as your business key, which has lots of benefits.
I've created a simple EJB application that uses JPA for persistence and have a problem whereby optimistic locking is not functioning as I would have expected.
The application contains a class named Site which defines the model for a table named SITE in the database. The SITE table contains a column named ROW_VERSION which is referenced in the Site class using the #version annotation.
Whenever the record is updated, the ROW_VERSION is incremented by 1. So far, so good.
The problem arises when the row has changed in the time between the application reading the row using the EntityManager find method and the row being updated by the EntityManager merge method. As the ROW_VERSION for the row has been incremented by 1 and therefore is not the same as when the EntityManager find method was called, I would expect an OptimisticLockException to be thrown, but instead the changes are written to the table and in turn overwriting the changes made by the other process.
The application is running on WebSphere 8.5 and is using OpenJPA provided by the container.
Have I mis-understood how optimistic locking is supposed to work or is there something else that I need to do to make the OptimisticLockException occur?
The Site class is as follows:
#Entity
#Table(name="SITE")
public class Site {
#Id
#Column(name="SITE_ID")
private int id;
#Column(name="SITE_NAME")
private String siteName;
#Column(name="SITE_ADDRESS")
private String address;
#Column(name="ROW_VERSION")
#Version
private long rowVersion;
//getters and setters
}
The application makes uses of the Generic DAO wrapper class to invoke the EntityManager methods. The contents of the class are as follows:
public abstract class GenericDAO<T> {
private final static String UNIT_NAME = "Test4EJB";
#PersistenceContext(unitName = UNIT_NAME)
private EntityManager em;
private Class<T> entityClass;
public GenericDAO(Class<T> entityClass) {
this.entityClass = entityClass;
}
public T update(T entity) {
return em.merge(entity);
}
public T find(int entityID) {
return em.find(entityClass, entityID);
}
//other methods
}
Update - I've done some more investigation and have found this http://pic.dhe.ibm.com/infocenter/wasinfo/v8r0/index.jsp?topic=%2Fcom.ibm.websphere.nd.multiplatform.doc%2Finfo%2Fae%2Fae%2Fcejb_genversionID.html but even when I've added the #VersionColumn and #VersionStrategy annotations I still cannot get the OptimisticLockException to be thrown.