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Synchronized block throwing DuplicateKeyException

Below is my class which is under threaded spring executors. Based on the type of source/service TAXP, TAXS, TAXT methods are getting called.
Logic is if the 'taxInfo.getGroupingId()' is already present in primary tax table do not insert, else insert primary table.
All secondary and tertiary tables records are inserted. TAXP, TAXS, TAXT are the topics and they receive data anytime. there might be milllisecond gap or at the same time the data would be sent so the blocks are synchroized.
All the 3 methods are called from 3 different thread executors.
executor1.insertPrimaryTaxInfo(taxInfo);
executor2.insertSecTaxInfo(taxInfo);
executor3.insertTerTaxInfo(taxInfo);
#Service
#Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public class TaxServiceImpl implements TaxService {
private static final Logger LOG = LogManager.getLogger(ScanServiceImpl.class);
// TAXP
#Override
#Transactional(propagation = Propagation.REQUIRED, rollbackFor = TaxServiceException.class)
public void insertPrimaryTaxInfo(TaxInfo taxInfo) throws TaxServiceException {
String taxId = null;
try {
synchronized (this) {
taxId = taxMapper.checkExists(taxInfo.getGroupingId());
if (taxId == null) {
taxMapper.insertTaxInfo(taxInfo); // primary tax table
}
}
LOG.info("tax id -- " + taxId);
} catch (Exception ex) {
LOG.error("Error inserting txId for " + taxInfo.getGroupingId()
+ ex);
throw new TaxServiceException(ex);
}
}
// TAXS
#Override
#Transactional(propagation = Propagation.REQUIRED, rollbackFor = TaxServiceException.class)
public void insertSecTaxInfo(TaxInfo taxInfo) throws TaxServiceException {
String taxId = null;
try {
synchronized (this) {
taxId = taxMapper.checkExists(taxInfo.getGroupingId());
if (taxId == null) {
taxMapper.insertTaxInfo(taxInfo); // primary tax table
}
}
taxMapper.insertIntoSecTable(taxInfo); // secondary tax table
LOG.info("tax id -- " + taxId);
} catch (Exception ex) {
LOG.error("Error inserting txId for " + taxInfo.getGroupingId()
+ ex);
throw new TaxServiceException(ex);
}
}
// TAXT
#Override
#Transactional(propagation = Propagation.REQUIRED, rollbackFor = TaxServiceException.class)
public void insertTerTaxInfo(TaxInfo taxInfo) throws TaxServiceException {
String taxId = null;
try {
synchronized (this) {
taxId = taxMapper.checkExists(taxInfo.getGroupingId());
if (taxId == null) {
taxMapper.insertTaxInfo(taxInfo); // primary tax table
}
}
taxMapper.insertIntoSecTable(taxInfo); // secondary tax table
taxMapper.insertIntoTerTable(taxInfo); // Tertiary tax table
LOG.info("tax id -- " + taxId);
} catch (Exception ex) {
LOG.error("Error inserting txId for " + taxInfo.getGroupingId()
+ ex);
throw new TaxServiceException(ex);
}
}
}
The issue is when TAXP, TAXS, TAXT are getting data at the same time, and the 3 above methods are called simultaneously. At a millisecond difference one of the thread inserts into primary table and the other thread trying to do the same but finds a record already exisitng in the table and throws duplicate key excepiton.
Im getting the below exception:
"com.data.exception.TaxServiceException: org.springframework.dao.DuplicateKeyException:
### Error updating database. Cause: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (TAXDB2.TAX_PK) violated
The reason for synchrnozing the block is to overcome this exception. What is wrong with the above code?

It looks like you may be attempting to generate non guid based primary keys in your application instead of letting the database generate them and running into conflicts.
Its a losing battle to attempt to synchronize database access in your application. You should be letting the database manage the concurrency through its existing mechanisms. For more information refer to ACID. Additionaly, it is very instructive to lookup the current Isolation level on your database implementation and what it does in comparison to the others. For example SQL Server docs Understanding Isolation Levels

Spring - Two hibernate update queries are executed instead of one

I am working Spring and Hibernate. I have a requirement where I need to update a particular field by adding a number to it. Since multiple threads could execute it at the same time, while updating I check the field value with the old value. So if nothing was updated that means it was incremented by some other thread and we trigger a retry.
CompanyService
public Company getAndIncrementRequestId(final int companyId, int retry) throws Exception {
Optional<Company> companyOptional = companyRepository.findById(companyId);
if (!companyOptional.isPresent()) {
throw new EntityNotFoundException("Company not found for given id" + companyId);
}
Company company = companyOptional.get();
int oldRequestId = company.getRequestId();
int requestId;
if (oldRequestId == Integer.MAX_VALUE) {
requestId = 1;
} else {
requestId = oldRequestId + 1;
}
company.setRequestId(requestId); //--------------------------> PROBLEM
int result = companyRepository.updateRequestId(companyId, requestId, oldRequestId);
if (result == 0) {
if (retry < 0) {
throw new Exception("Unable to get requestId");
}
LOG.warn("Retrying since there was some update on requestId by some other thread");
try {
TimeUnit.MILLISECONDS.sleep(100);
} catch (InterruptedException e) {
LOG.warn("Unexpected InterruptException occurred while trying to get requestId");
}
return getAndIncrementRequestId(companyId, retry - 1);
}
return company;
}
CompanyRepository
#Transactional
public interface CompanyRepository extends CrudRepository<Company, Integer> {
Optional<Company> findById(String id);
#Modifying(clearAutomatically = true)
#Query("update Company c set c.requestId = :requestId WHERE c.id = :companyId AND c.requestId = :oldRequestId")
int updateRequestId(#Param("companyId") Integer companyId, #Param("requestId") Integer requestId,#Param("oldRequestId") Integer oldRequestId);
}
But this above code in Service will trigger two hibernate updates one which set the requestId with lastest requestId and the other the actual update. Could observe two queries in the log after setting show-sql as true.
But if the line ,
company.setRequestId(requestId);
Is moved down after the companyRepository.updateRequestId() it works fine.
Working CompanyService
public Company getAndIncrementRequestId(final int companyId, int retry) throws Exception {
Optional<Company> companyOptional = companyRepository.findById(companyId);
if (!companyOptional.isPresent()) {
throw new EntityNotFoundException("Company not found for given id" + companyId);
}
Company company = companyOptional.get();
int oldRequestId = company.getRequestId();
int requestId;
if (oldRequestId == Integer.MAX_VALUE) {
requestId = 1;
} else {
requestId = oldRequestId + 1;
}
int result = companyRepository.updateRequestId(companyId, requestId, oldRequestId);
if (result == 0) {
if (retry < 0) {
throw new Exception("Unable to get requestId");
}
LOG.warn("Retrying since there was some update on requestId by some other thread");
try {
TimeUnit.MILLISECONDS.sleep(100);
} catch (InterruptedException e) {
LOG.warn("Unexpected InterruptException occurred while trying to get requestId");
}
return getAndIncrementRequestId(companyId, retry - 1);
}
company.setRequestId(requestId); //--------------------------> PROBLEM DOES NOT EXISTS
return company;
}
Sp my question why are there two queries when I have not even passed the entity Company anywhere..?

It is because when you do "companyRepository.findById(companyId);" the returned company is returned in managed state.
So , when in case 1 you set the request id before invoking "companyRepository.updateRequestId(companyId, requestId, oldRequestId);", a transaction object is created in the company repository which executes all the pending updates of the managed entity plus the query of the method "updateRequestId" also gets fired.
While in second case, since you have written set statement after invoking "companyRepository.updateRequestId(companyId, requestId, oldRequestId);", that is why the update on managed object never gets fired because it does not get any transaction

Java - How to delete an entity from Google Cloud Datastore

Architecture: I have a web application from where I'm interacting with the Datastore and a client (raspberry pi) which is calling methods from the web application using Google Cloud Endpoints.
I have to add that I'm not very familiar with web applications and I assume that something's wrong with the setConsumed() method because I can see the call of /create in the app engine dashboard but there's no entry for /setConsumed.
I'm able to add entities to the Datastore using objectify:
//client method
private static void sendSensorData(long index, String serialNumber) throws IOException {
SensorData data = new SensorData();
data.setId(index+1);
data.setSerialNumber(serialNumber);
sensor.create(data).execute();
}
//api method in the web application
#ApiMethod(name = "create", httpMethod = "post")
public SensorData create(SensorData data, User user) {
// check if user is authenticated and authorized
if (user == null) {
log.warning("User is not authenticated");
System.out.println("Trying to authenticate user...");
createUser(user);
// throw new RuntimeException("Authentication required!");
} else if (!Constants.EMAIL_ADDRESS.equals(user.getEmail())) {
log.warning("User is not authorised, email: " + user.getEmail());
throw new RuntimeException("Not authorised!");
}
data.save();
return data;
}
//method in entity class SensorData
public Key<SensorData> save() {
return ofy().save().entity(this).now();
}
However, I'm not able to delete an entity from the datastore using the following code.
EDIT: There are many logs of the create-request in Stackdriver Logging, but none of setConsumed(). So it seems like the calls don't even reach the API although both methods are in the same class.
EDIT 2: The entity gets removed when I invoke the method from the Powershell so the problem is most likely on client side.
//client method
private static void removeSensorData(long index) throws IOException {
sensor.setConsumed(index+1);
}
//api method in the web application
#ApiMethod(name = "setConsumed", httpMethod = "put")
public void setConsumed(#Named("id") Long id, User user) {
// check if user is authenticated and authorized
if (user == null) {
log.warning("User is not authenticated");
System.out.println("Trying to authenticate user...");
createUser(user);
// throw new RuntimeException("Authentication required!");
} else if (!Constants.EMAIL_ADDRESS.equals(user.getEmail())) {
log.warning("User is not authorised, email: " + user.getEmail());
throw new RuntimeException("Not authorised!");
}
Key serialKey = KeyFactory.createKey("SensorData", id);
datastore.delete(serialKey);
}

This is what I follow to delete an entity from datastore.
public boolean deleteEntity(String propertyValue) {
String entityName = "YOUR_ENTITY_NAME";
String gql = "SELECT * FROM "+entityName +" WHERE property= "+propertyValue+"";
Query<Entity> query = Query.newGqlQueryBuilder(Query.ResultType.ENTITY, gql)
.setAllowLiteral(true).build();
try{
QueryResults<Entity> results = ds.run(query);
if (results.hasNext()) {
Entity rs = results.next();
ds.delete(rs.getKey());
return true;
}
return false;
}catch(Exception e){
logger.error(e.getMessage());
return false;
}
}
If you don't want to use literals, you can also use binding as follows:
String gql = "SELECT * FROM "+entityName+" WHERE property1= #prop1 AND property2= #prop2";
Query<Entity> query = Query.newGqlQueryBuilder(Query.ResultType.ENTITY, gql)
.setBinding("prop1", propertyValue1)
.setBinding("prop2", propertyValue2)
.build();
Hope this helps.

I was able to solve it by myself finally!
The problem was just related to the data type of the index used for removeSensorData(long index) which came out of a for-loop and therefore was an Integer instead of a long.

Unusable session in Modeshape - JCR Exception

Sometimes when I use multiple Modeshape actions inside one function I get this error:
javax.jcr.RepositoryException: The session with an ID of '060742fc6' has been closed and can no longer be used.
I couldn't find any explanations of this on the web. Here is what I call:
myFunction( service.doSomething ( service.getStuff ( id, "en_EN" ).getPath() ) );
doSomething, getStuff:
#Interceptors({Foo.class, TraceInterceptor.class})
#Override
public Node doSomething(final String bar) throws RepositoryException {
return modeshape.execute(new JcrHandler<Node>() {
#Override
public Node execute(Session session) throws RepositoryException {
return session.getNode(bar);
}
});
}
#Interceptors(TraceInterceptor.class)
#Override
public ObjectExtended getStuff(final String query, final String language)
throws RepositoryException {
return modeshape.execute(new JcrHandler<ObjectExtended>() {
#Override
public ObjectExtendedexecute(Session session)
throws RepositoryException {
QueryManager queryManager = session.getWorkspace().getQueryManager();
ObjectExtendeditem = null;
String queryWrapped =
"select * from [th:this] as c where name(c)='lang_"
+ language + "' and c.[th:mylabel] "
+ "= '" + queryStr + "'";
LOGGER.debug("Query: " + queryWrapped);
Query query =
queryManager.createQuery(queryWrapped,Query.JCR_SQL2);
QueryResult result = query.execute();
NodeIterator iter = result.getNodes();
while (iter.hasNext()) {
Node node = iter.nextNode().getParent();
if (node.isNodeType("th:term")) {
item = new ObjectExtended();
item.setLabel(getLabel(language, node));
item.setPath(node.getPath());
}
}
return item;
}
});
}
Why is this happening please? What am I doing wrong?

That error message means one of two thing: either the repository is being shutdown, or the Session.logout() method is being called.
None of the above code shows how your sessions are being managed, and you don't say whether you are using a framework. But I suspect that somehow you are holding onto a Session too long (perhaps after your framework is closing the session), or the Session is leaking to multiple threads, and one thread is attempting to use it after the other has closed it.
The latter could be a real problem: while passing a single Session instance from one thread to another is okay (as long as the original thread no longer uses it), but per the JCR 2.0 specification Session instances are not threadsafe and should not be concurrently used by multiple threads.
If you're creating the Session in your code, it's often good to use a try-finally block:
Session session = null;
try {
session = ... // acquire the session
// use the session, including 0 or more calls to 'save()'
} catch ( RepositoryException e ) {
// handle it
} finally {
if ( session != null ) {
try {
session.logout();
} finally {
session = null;
}
}
}
Note that logout() does not throw a RepositoryException, so the above form usually works well. Of course, if you know you're not using session later on in the method, you don't need the inner try-finally to null the session reference:
Session session = null;
try {
session = ... // acquire the session
// use the session, including 0 or more calls to 'save()'
} catch ( RepositoryException e ) {
// handle it
} finally {
if ( session != null ) session.logout();
}
This kind of logic can easily be encapsulated.

OpenJpa merge detached object

I'm wondering if the way I use to save my entities with OpenJpa 2 is correct.
I receive object from a rest service that I deserialize, then to save this instance :
Begin the transaction
Retrieve the instance from the DB (even though I've already got this instance)
Copy the attributes from the detached instance to the instance retrieved from the DB
Call the merge
Commit the transaction
In case of a complex entity model with compsitions, it becomes painful!
public boolean save(Collection<Event> events) throws DataException {
if (events == null) {
throw new DataException("Cannot save null events");
}
EntityManager em = getEntityManager();
try {
em.getTransaction().begin();
for (Event event : events) {
boolean add = true;
if(event.getKey() > 0){
Event previousEvent = em.find(Event.class, event.getKey());
if (previousEvent != null) {
//update
previousEvent.setTitle(event.getTitle());
previousEvent.setDate(event.getDate());
previousEvent.setDescription(event.getDescription());
List<Member> participants = new ArrayList<>();
for(Member m : event.getParticipants()){
Member participant = em.find(Member.class, m.getKey());
if(participant != null){
participants.add(participant);
}
}
previousEvent.setParticipants(participants);
List<Member> registrants = new ArrayList<>();
for(Member m : event.getRegistrants()){
Member registrant = em.find(Member.class, m.getKey());
if(registrant != null){
participants.add(registrant);
}
}
previousEvent.setRegistrants(registrants);
em.merge(previousEvent);
add = false;
}
}
if(add) {
//add
em.persist(event);
}
}
em.getTransaction().commit();
} catch (PersistenceException pe) {
pe.printStackTrace();
throw new DataException("An error occured while saving the event", pe);
} finally {
em.close();
}
return true;
}
Any suggestion?
THanks

Per Chris' comment - you should be able to just call em.merge(event) and let JPA handle all of it. It should automatically handle creating a new Event row if needed, updating the Event attributes, and updating or creating the contained objects as well.