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JPA save with multiple entities not rolling back when inside Spring #Transactional and rollback for Exception.class enabled
(1 answer)
Closed 3 years ago.
I am trying to create an API for transferring funds
i.e withdrawal and deposit.
I performed the transaction using #Transactional Annotation.
But there are certain criteria i.e if bank account number doesn't exist that should through an Runtime exception.
I will attach the code within. Now, when transferBalanceMethod is called and if depositor bank Account doesn't exist than amount that is withdrawn should also be rolled back.
But that isn't happening. Means when fund transfer occurs from account A to Account B of 1000 rupees then if an exception occurs in B's deposition then the withdraw in A Account should also be withdrawn.
I tried #Transactional annotation and also rollbackFor property of the Exception class too
I tried to add #Transaction annotation for deposit and withdraw method too but that we use the same transaction because we use propogation Required**
Model Class//This is the Model Class
//All Imports
#Entity
public class BankAccount {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Integer id;
#Column(name = "bankAccountNumber", nullable = false,unique = true)
#NotNull
#Size(min = 5, message = "Bank account number should be greater than 5 characters")
private String bankAccountNumber;
#NotNull
#Column(name = "balance", nullable = false)
#Min(1000)
private Long balance;
//Getter Setter and Constructor
**Controller File**//This is the Controller Class
//All imports and other stuff such as #RestController, #Autowired
#GetMapping("/bankaccount/transfer")
public void transferBalance(#RequestParam("bankAccountNo1") String bankAccountNo1, #RequestParam("bankAccountNo2") String bankAccountNo2,
#RequestParam("balance") Long balance) throws RuntimeException
{
bankService.transferBalance(bankAccountNo1,bankAccountNo2, balance);
}
}
**Service File:-**//This is Service Layer
//All imports
#Service
public class BankService {
#Autowired
private BankRepository bankRepository;
#Autowired
private ModelMapper modelMapper;
public List<BankAccountDTO> getAllBankAccount() {
List<BankAccountDTO> bankAccountDTO = new ArrayList<BankAccountDTO>();
List<BankAccount> bankAccount = bankRepository.findAll();
for (BankAccount b : bankAccount) {
bankAccountDTO.add(modelMapper.map(b, BankAccountDTO.class));
}
return bankAccountDTO;
}
public ResponseEntity<?> getIndividualBankAccount(String bankAccountNumber) {
BankAccount bankAccount = bankRepository.findByBankAccountNumber(bankAccountNumber);
if (bankAccount == null) {
return new ResponseEntity<>("Account not found", HttpStatus.BAD_REQUEST);
} else {
return new ResponseEntity<>(
modelMapper.map(bankRepository.findByBankAccountNumber(bankAccountNumber), BankAccountDTO.class),
HttpStatus.OK);
}
}
public Object addBankAccount(BankAccountDTO bankAccountDTO) {
return bankRepository.save(modelMapper.map(bankAccountDTO, BankAccount.class));
}
#Transactional(propagation = Propagation.REQUIRED)
public void depositBalance(String bankAccountNumber, Long balance) throws RuntimeException {
BankAccount bankAccNo = bankRepository.findByBankAccountNumber(bankAccountNumber);
if (bankAccNo == null) {
throw new RuntimeException("Bank Accout Number is not found : " + bankAccountNumber);
} else {
if (balance <= 0) {
throw new RuntimeException("Please deposit appropriate balance");
} else {
Long amount = bankAccNo.getBalance() + balance;
bankAccNo.setBalance(amount);
bankRepository.save(bankAccNo);
}
}
}
#Transactional(propagation = Propagation.REQUIRED)
public void withdrawBalance(String bankAccountNumber, Long balance) throws RuntimeException {
BankAccount bankAccNo = bankRepository.findByBankAccountNumber(bankAccountNumber);
if (bankAccNo == null) {
throw new RuntimeException("Bank Account not found :" + bankAccountNumber);
} else {
if (balance <= 0) {
throw new RuntimeException("Please withdraw appropriate balance");
} else {
Long amount = bankAccNo.getBalance() - balance;
if (amount < 1000) {
throw new RuntimeException("Sorry Cannot withdraw.Your minimum balance should be thousand rupees!");
} else {
bankAccNo.setBalance(amount);
bankRepository.save(bankAccNo);
}
}
}
}
#Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = RuntimeException.class)
public void transferBalance(String bankAccountNo1, String bankAccountNo2, Long balance) throws RuntimeException {
try {
withdrawBalance(bankAccountNo1, balance);
depositBalance(bankAccountNo2, balance);
} catch (RuntimeException e) {
throw e;
}
}
}
Only runtime exceptions will trigger a rollback operation within a spring transaction annotation, if you are using custom annotations you need to make sure you either made then extend from RuntimeException or that you add an specific rollback clause to your transaction so that it rollback in that specific exception.
maybe this answer will be useful for you:
Spring transaction: rollback on Exception or Throwable
also to go to the official transactional documentation of spring here:
https://docs.spring.io/spring/docs/4.2.x/spring-framework-reference/html/transaction.html
Related
Is there any way to save the true entities in the DB even after any exception occurred during saveAll execution?
For example, I have 100 entities and 2 entities result in data violation exception but I still want to save the other 98 entities in DB. As of now if a data violation exception occurred it save none in the DB.
#Autowired
BillingJpaRepository billingJpaRepository;
#Transactional
private void saveBillingRecords(List<BillingInfo> billingInfos) {
try {
billingJpaRepository.saveAll(billingInfos);
} catch (DataIntegrityViolationException dataIntegrityViolationException) {
this.saveBillingRecordsIndividually(billingInfos);
} catch (Exception ex) {
throw ex;
}
}
#Transactional
private void saveBillingRecordsIndividually(List<BillingInfo> billingInfos) {
for(BillingInfo billingInfo : billingInfos) {
try {
billingJpaRepository.save(billingInfo);
} catch (DataIntegrityViolationException dataIntegrityViolationException) {
logger.error("data voilation exception occured");
} catch (Exception ex) {
throw ex;
}
}
}
Because of this, I have to save all true entities individually which is a performance hit. Since all the entities will be in detached stated after saveAll it will execute merge operation instead of persist and because of this, an extra SELECT statement will be triggered for each save operation. Below is my entity structure
#AllArgsConstructor
#NoArgsConstructor
#Data
#Entity
#Table(name= "BLI_INFO")
public class BillingInfo implements Persistable<long> {
#Id
#Column(name = "BLI_ID")
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_gen")
#SequenceGenerator(sequenceName = "BLI_ID_SEQ", name = "id_gen", allocationSize = 1)
private long billingId;
...
// rest of the fields
...
#Transient
private boolean isNew = true;
#PrePersist
#PostLoad
void markNotNew() {
this.isNew = false;
}
#Override
public boolean isNew(){
return true;
}
}
We have two tables that have a one to many relationship. When we insert multiple records into the child table across multiple threads (more specifically across multiple REST web requests) we are running into lost update issues due to a race condition.
What we need to be able to do is have JPA recognize that the entity has been updated elsewhere prior to inserting the child record. I've tried using the #Version annotation approach but that doesn't seem to do the trick as the update/insert (I guess...) is happening on another table. I tried adding a version timestamp column on the parent table that is updated on every update but that didn't seem to do the trick either.
I think what I actually need to do is get a reference to the EntityManager directly so that I can issue a lock() command on the record prior to calling save(). I'm just too new to Spring to know if
A) that is indeed the correct approach,
B) if there is a better/easier way to do what we are trying to accomplish, and
C) how to actually do that.
Also, I am aware of the #OneToMany annotation but that didn't seem to do anything.
I've truncated the code below for brevity and I also created a trimmed down version of the code that demonstrates the problem and will hopefully make it easier to see what I am trying to do. In the test if you change the thread pool number to 1 you can see the test pass.
Engagement class:
#Entity
public class Engagement implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long id;
#ElementCollection(fetch = EAGER)
private List<String> assignedUsers;
#Version
private Long version;
private LocalDateTime updatedOn;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Long getVersion(){return version;}
public void setVersion(Long version){this.version = version;}
public LocalDateTime getUpdatedOn(){
return updatedOn;
}
public void setUpdatedOn(LocalDateTime updatedOn) {
this.updatedOn = updatedOn;
}
public List<String> getAssignedUsers() {
return assignedUsers;
}
public void setAssignedUsers(List<String> assignedUsers) {
this.assignedUsers = assignedUsers;
}
public Engagement() {
}
}
User class:
public final class User {
private final String name;
private final String email;
private final String userId;
private final List<Engagement> engagements;
#ConstructorProperties({"roles", "name", "email", "userId", "engagements"})
User(String name, String email, String userId, List<Engagement> engagements) {
this.name = name;
this.email = email;
this.userId = userId;
this.engagements = engagements;
}
public static User.UserBuilder builder() {
return new User.UserBuilder();
}
public String getName() {
return this.name;
}
public String getEmail() {
return this.email;
}
public String getUserId() {
return this.userId;
}
public List<Engagement> getEngagements() {
return this.engagements;
}
public static final class UserBuilder {
private String name;
private String email;
private String userId;
private List<Engagement> engagements;
UserBuilder() {
}
public User.UserBuilder name(String name) {
this.name = name;
return this;
}
public User.UserBuilder email(String email) {
this.email = email;
return this;
}
public User.UserBuilder userId(String userId) {
this.userId = userId;
return this;
}
public User.UserBuilder engagements(List<Engagement> engagements) {
this.engagements = engagements;
return this;
}
public User build() {
return new User(this.name, this.email, this.userId, this.engagements);
}
public String toString() {
return "User.UserBuilder(name=" + this.name + ", email=" + this.email + ", userId=" + this.userId + ", engagements=" + this.engagements + ")";
}
}
}
Thread test:
#RunWith(SpringJUnit4ClassRunner.class)
#SpringBootTest
public class EngagementTest {
#Mock
UsersAuthService usersService;
#Autowired
EngagementsRepository engagementsRepository;
UsersAuthService authService;
#Before
public void init() {
MockitoAnnotations.initMocks(this);
authService = new UsersAuthServiceImpl(usersService, engagementsRepository);
}
#Test
public void addingMultipleUsersAtOnceSucceeds() throws InterruptedException {
Long engagementId = 1L;
String userId1 = "user1";
String userId2 = "user2";
String userId3 = "user3";
String userId4 = "user4";
String userId5 = "user5";
String auth = "asdf";
User adminUser = User.builder()
.userId("adminUser")
.email("user#user.com")
.name("Admin User")
.build();
Engagement engagement = new Engagement();
engagement.setAssignedUsers(new ArrayList<>());
engagement.getAssignedUsers().add(adminUser.getUserId());
engagementsRepository.save(engagement);
ExecutorService executorService = Executors.newFixedThreadPool(5);//change this to 1 to see the test pass
List<Callable<Engagement>> callableList = Arrays.asList(
addUserThread(engagementId, userId1, auth, adminUser),
addUserThread(engagementId, userId2, auth, adminUser),
addUserThread(engagementId, userId3, auth, adminUser),
addUserThread(engagementId, userId4, auth, adminUser),
addUserThread(engagementId, userId5, auth, adminUser));
executorService.invokeAll(callableList);
Engagement after = engagementsRepository.findById(engagementId);
assertEquals(6, after.getAssignedUsers().size());
}
private Callable<Engagement> addUserThread(Long engagementId, String userId1, String auth, User adminUser) {
return () -> authService.addUserTo(engagementId, userId1, auth, adminUser);
}
}
What's happening here is that you submit the callbacks for execution but never actually wait for their completion before checking the result. You need to use the List<Future<Engagement>> to actually wait for the results to complete before proceeding.
Something like this would do the trick:
executorService.invokeAll(callableList).forEach(it -> {
try {
it.get(500, TimeUnit.MILLISECONDS);
} catch (InterruptedException | ExecutionException | TimeoutException e) {
e.printStackTrace();
}
});
Note that this is not a proper way to deal with the exception case but it causes the code to wait for completion. If you have that in place you see the threads properly rejecting some of the updates with an ObjectOptimisticLockingFailureException:
java.util.concurrent.ExecutionException: org.springframework.orm.ObjectOptimisticLockingFailureException: Object of class [com.example.racecondition.engagement.Engagement] with identifier [1]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [com.example.racecondition.engagement.Engagement#1]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:206)
at com.example.racecondition.EngagementTest.lambda$0(EngagementTest.java:68)
at java.util.ArrayList.forEach(ArrayList.java:1257)
at com.example.racecondition.EngagementTest.addingMultipleUsersAtOnceSucceeds(EngagementTest.java:66)
What's weird about the test case beyond that is that UsersAuthServiceImpl carries an #Transactional but the test case manually instantiates that class, so that there's no transactional proxy in place already. This causes the calls to findById(…) and save(…) from within addToUser(…) to run in two transactions. Tweaking that doesn't change the output though.
I think what I actually need to do is get a reference to the EntityManager directly so that I can issue a lock() command on the record prior to calling save(). I'm just too new to Spring to know if
A) that is indeed the correct approach,
If I understand you correctly you want to basically force a version increment on an entity so that if multiple threads do that one fails.
You can indeed achieve that by locking the entity in question using LockModeType.PESSIMISTIC_FORCE_INCREMENT or LockModeType.OPTIMISTIC_FORCE_INCREMENT.
B) if there is a better/easier way to do what we are trying to accomplish, and
C) how to actually do that.
With Spring Data probably the best way to do that is using the #Lock annotation on the method you use to load the entity.
I have two methods (in a Spring boot application) that handle an entity. The entity has two fields, both boolean isDefault and isPdfGenerated. The first method (which is called from a controller) changes the isDefault flag when a new entity is created while the second one (called from a #Scheduled annotated method) changes the isPdfGenrated after it generates a pdf file for that entity.
My problem is that sometimes the second method finds entities with the isPdfGenerated flag set to false even though the file has been generated and saved in the database.
Both the methods have the #Transactional annotation and the repository interface for the entity extends JpARepository.
My guess is that the first method loads the entity from the database before the second method does but saves the entity after the second method does its job, thus overriding the isPdfGenerated flag.
Is this possible ? If the answer is yes, how should one handle such cases ? Shouldn't JPARepository handle the case when an entity gets updated from an external source ?
Bellow is some code to better illustrate the situation.
MyController:
#Controller
#RequestMapping("/customers")
public class MyController {
#Autowired
private EntityService entityService;
#RequestMapping(value = "/{id}/changeDefault", method = RequestMethod.POST)
public String changeDefault(#PathVariable("id") Long customerId, #ModelAttribute EntityForm entityForm, Model model) {
Entity newDefaultEntity = entityService.updateDefaultEntity(customerId, entityForm);
if (newDefaultEntity == null)
return "redirect:/customers/" + customerId;
return "redirect:/customers/" + customerId + "/entity/default;
}
}
EntityService:
import org.springframework.transaction.annotation.Transactional;
#Service
public class EntityService {
#Autowired
private EntityRepository entityRepository;
#Autowired
private CustomerRepository customerRepository;
#Transactional
public Entity updateDefaultEntity(Long customerId, submittedData) {
Customer customer = customerRepository.findById(customerId);
if(customer == null)
return customer; // I know there are better ways to do this
Entity currentDefaultEntity = entityRepository.findUniqueByCustomerAndDefaultFlag(customer, true);
if(currentDefaultEntity == null)
return null; // I know there are better ways to do this also
Entity newDefaultEntity = new Entity();
newDefaultEntity.setField1(submittedData.getField1());
newDefaultEntity.setField2(submittedData.getField2());
newDefaultEntity.setCustomer(customer);
oldDefaultEntity.setDefaultFlag(false);
newDefaultEntity.setDefaultFlag(true);
entityRepository.save(newDefaultEntity);
}
#Transactional
public void generatePdfDocument(Entity entity) {
Document pdfDocument = generateDocument(entity);
if(pdfDocument == null)
return;
documentRepository.save(pdfDocument);
entity.setPdfGeneratedFlag(true);
entityRepository.save(entity);
}
}
ScheduledTasks:
#Component
public class ScheduledTasks {
private static final int SECOND_IN_MILLISECONDS = 1000;
private static final int MINUTE_IN_SECONDS = 60;
#Autowired
private EntityRepository entityRepository;
#Autowired
private DocumentService documentService;
#Scheduled(fixedDelay = 20 * SECOND_IN_MILLISECONDS)
#Transactional
public void generateDocuments() {
List<Quotation> quotationList = entityRepository.findByPdfGeneratedFlag(false);
for(Entity entity : entitiesList) {
documentService.generatePdfDocument(entity);
}
}
}
DocumentService:
#Service
public class DocumentService {
#Autowired
private EntityRepository entityRepository;
#Autowired
private DocumentRepository documentRepository;
#Transactional
public void generatePdfDocument(Entity entity) {
Document pdfDocument = generateDocument(entity);
if(pdfDocument == null)
return;
documentRepository.save(pdfDocument);
entity.setPdfGeneratedFlag(true);
entityRepository.save(entity);
}
}
EntityRepository:
#Repository
public interface EntityRepository extends JpaRepository<Entity, Long> {
Entity findById(#Param("id") Long id);
List<Entity> findByPdfGeneratedFlag(#Param("is_pdf_generated") Boolean pdfGeneratedFlag);
Entity findUniqueByCustomerAndDefaultFlag(
#Param("customer") Customer customer,
#Param("defaultFlag") Boolean defaultFlag
);
}
DocumentRepository:
#Repository
public interface DocumentRepository extends JpaRepository<Document, Long> {
Document findById(#Param("id") Long id);
}
Entity:
#Entity
#Table(name = "entities")
#JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "id")
public class Entity {
private Long id;
private boolean defaultFlag;
private boolean pdfGeneratedFlag;
private String field1;
private String field2;
private Customer customer;
public Entity() { }
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#Column(name = "is_default")
public boolean isDefaultFlag() {
return defaultFlag;
}
public void setDefaultFlag(boolean defaultFlag) {
this.defaultFlag = defaultFlag;
}
#Column(name = "is_pdf_generated")
public boolean isPdfGeneratedFlag() {
return pdfGeneratedFlag;
}
public void setPdfGeneratedFlag(boolean pdfGeneratedFlag) {
this.pdfGeneratedFlag = pdfGeneratedFlag;
}
#Column(name = "field_1")
public String getField1() {
return field1;
}
public void setField1(String field1) {
this.field1 = field1;
}
#Column(name = "field_2")
public String getField2() {
return field2;
}
public void setField2(String field2) {
this.field2 = field2;
}
#ManyToOne
#JoinColumn(name = "customer_id", referencedColumnName = "id", nullable = false)
public Customer getCustomer() {
return customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Entity quotation = (Entity) o;
return id != null ? id.equals(entity.id) : entity.id == null;
}
#Override
public int hashCode() {
return id != null ? id.hashCode() : 0;
}
#Override
public String toString() {
return "Entity{" +
"id=" + id +
", pdfGeneratedFlag=" + pdfGeneratedFlag +
", defaultFlag=" + defaultFlag +
", field1=" + field1 +
", field2=" + field2 +
", customer=" + (customer == null ? null : customer.getId()) +
"}";
}
}
I have omitted the other classes because they are either POJOs ( EntityForm ) or the same as other domain model classes ( Document ).
If you're talking about a row on the database that is getting updated by another process after the first process has read it but before it has been updated, then you need to put in some sort of optimistic locking strategy.
This will be handled by the underlying ORM api (e.g. Hibernate or Eclipselink) rather than Spring Data (which will just handle an optimistic locking errors thrown by the ORM).
Have a look at this article. Bear in mind that if you want optimistic locking you need some way of determining a row's version. In JPA this is normally done using a column annotated with the #Version tag.
https://vladmihalcea.com/hibernate-locking-patterns-how-does-optimistic-lock-mode-work/
Model structure:
#MappedSuperclass
public class BaseModel<K extends Comparable> implements Serializable, Comparable<Object> {
private static final long serialVersionUID = 1L;
#Id
private K id;
#Version
private Integer version;
// getter/setter
}
#Entity
public class MyEntity extends BaseModel<String> {
// some fields and it's getter/setter
}
Record in my database for my_entity:
id: 1
version: 1
...
Below is my update method:
void update(String id, Integer currentVersion, ....) {
MyEntity myEntity = myRepository.findOne(id);
myEntity.setVersion(currentVersion);
// other assignments
myRepository.save(myEntity);
}
Below is the query being fired when this method is invoked.
update my_entity set version=?, x=?, y=?, ...
where id=? and version=?
I am expecting OptimisticLockException when currentVersion passed in above method is other than 1.
Can any body help me why I am not getting OptimisticLockException?
I am using spring-boot for my webmvc project.
Section 11.1.54 of the JPA specification notes that:
In general, fields or properties that are specified with the Version
annotation should not be updated by the application.
From experience, I can advise that some JPA providers (OpenJPA being one) actually throw an exception should you try to manually update the version field.
While not strictly an answer to your question, you can re-factor as below to ensure both portability between JPA providers and strict compliance with the JPA specification:
public void update(String id, Integer currentVersion) throws MyWrappedException {
MyEntity myEntity = myRepository.findOne(id);
if(currentVersion != myEntity.getVersion()){
throw new MyWrappedException();
}
myRepository.save(myEntity);
//still an issue here however: see below
}
Assuming your update(...) method is running in a transaction however you still have an issue with the above as section 3.4.5 of the JPA specification notes:
3.4.5 OptimisticLockException Provider implementations may defer writing to the database until the end of the transaction, when
consistent with the lock mode and flush mode settings in effect. In
this case, an optimistic lock check may not occur until commit time,
and the OptimisticLockException may be thrown in the "before
completion" phase of the commit. If the OptimisticLockException must
be caught or handled by the application, the flush method should be
used by the application to force the database writes to occur. This
will allow the application to catch and handle optimistic lock
exceptions.
Essentially then, 2 users can submit concurrent modifications for the same Entity. Both threads can pass the initial check however one will fail when the updates are flushed to the database which may be on transaction commit i.e. after your method has completed.
In order that you can catch and handle the OptimisticLock exception, your code should then look something like the below:
public void update(String id, Integer currentVersion) throws MyWrappedException {
MyEntity myEntity = myRepository.findOne(id);
if(currentVersion != myEntity.getVersion()){
throw new MyWrappedException();
}
myRepository.save(myEntity);
try{
myRepository.flush()
}
catch(OptimisticLockingFailureException ex){
throw new MyWrappedException();
}
}
Use EVICT before updating when using JPA. I did not get the #Version to work either. The property was increased but no exception was thrown when updating an object that had the wrong version-property.
The only thing I have got to work is to first EVICT the object and then save it. Then the HibernateOptimisticLockingException is thrown if the Version properties does not match.
Set the hibernates ShowSQL to 'true' to verify that the actual update sql ends with "where id=? and version=?". If the object is not evicted first, the update statement only has "where id=?", and that will (for obvious reasons) not work.
Optimistic hibernation lock works out of the box (You don't must put a version for Entity):
#Entity
#Table(name = "product")
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private Long quantity;
private Long likes;
#Version
private Long version;
public Product() {
}
//setter and getter
//equals and hashcode
repository
public interface ProductRepository extends JpaRepository<Product, Long> {}
service
#Service
public class ProductOptimisticLockingService {
private final ProductRepository productRepository;
public ProductOptimisticLockingService(ProductRepository productRepository) {
this.productRepository = productRepository;
}
#Transactional(readOnly = true)
public Product findById(Long id, String nameThread){
Product product =
productRepository
.findById(id)
.get();
System.out.printf(
"\n Select (%s) .... " +
"(id:) %d | (likes:) %d | (quantity:) %d | (version:) %d \n",
nameThread,
product.getId(),
product.getLikes(),
product.getQuantity(),
product.getVersion()
);
return product;
}
#Transactional(isolation = Isolation.READ_COMMITTED)
public void updateWithOptimisticLocking(Product product, String nameThread) {
try {
productRepository.save(product);
} catch (ObjectOptimisticLockingFailureException ex) {
System.out.printf(
"\n (%s) Another transaction is already working with a string with an ID: %d \n",
nameThread,
product.getId()
);
}
System.out.printf("\n--- Update has been performed (%s)---\n", nameThread);
}
}
test
#SpringBootTest
class ProductOptimisticLockingServiceTest {
#Autowired
private ProductOptimisticLockingService productService;
#Autowired
private ProductRepository productRepository;
#Test
void saveWithOptimisticLocking() {
/*ID may be - 1 or another. You must put the ID to pass in your methods. You must think how to write right your tests*/
Product product = new Product();
product.setLikes(7L);
product.setQuantity(5L);
productRepository.save(product);
ExecutorService executor = Executors.newFixedThreadPool(2);
Lock lockService = new ReentrantLock();
Runnable taskForAlice = makeTaskForAlice(lockService);
Runnable taskForBob = makeTaskForBob(lockService);
executor.submit(taskForAlice);
executor.submit(taskForBob);
executorServiceMethod(executor);
}
/*------ Alice-----*/
private Runnable makeTaskForAlice(Lock lockService){
return () -> {
System.out.println("Thread-1 - Alice");
Product product;
lockService.lock();
try{
product = productService
.findById(1L, "Thread-1 - Alice");
}finally {
lockService.unlock();
}
setPause(1000L); /*a pause is needed in order for the 2nd transaction to attempt
read the line from which the 1st transaction started working*/
lockService.lock();
try{
product.setQuantity(6L);
product.setLikes(7L);
update(product,"Thread-1 - Alice");
}finally {
lockService.unlock();
}
System.out.println("Thread-1 - Alice - end");
};
}
/*------ Bob-----*/
private Runnable makeTaskForBob(Lock lockService){
return () -> {
/*the pause makes it possible to start the transaction first
from Alice*/
setPause(50L);
System.out.println("Thread-2 - Bob");
Product product;
lockService.lock();
try{
product = findProduct("Thread-2 - Bob");
}finally {
lockService.unlock();
}
setPause(3000L); /*a pause is needed in order for the 1st transaction to update
the string that the 2nd transaction is trying to work with*/
lockService.lock();
try{
product.setQuantity(5L);
product.setLikes(10L);
update(product,"Thread-2 - Bob");
}finally {
lockService.unlock();
}
System.out.println("Thread-2 - Bob - end");
};
}
private void update(Product product, String nameThread){
productService
.updateWithOptimisticLocking(product, nameThread);
}
private Product findProduct(String nameThread){
return productService
.findById(1L, nameThread);
}
private void setPause(long timeOut){
try {
TimeUnit.MILLISECONDS.sleep(timeOut);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void executorServiceMethod(ExecutorService executor){
try {
executor.awaitTermination(10L, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
}
executor.shutdown();
}
}
I have a simple Hibernate entity:
#Entity
#Table(name = "keyword",
uniqueConstraints = #UniqueConstraint(columnNames = { "keyword" }))
public class KeywordEntity implements Serializable {
private Long id;
private String keyword;
public KeywordEntity() {
}
#Id
#GeneratedValue
#Column(unique = true, updatable=false, nullable = false)
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
#Column(name="keyword")
public String getKeyword() {
return this.keyword;
}
public void setKeyword(String keyword) {
this.keyword = keyword;
}
}
DAO for it:
#Component
#Scope("prototype")
public class KeywordDao {
protected SessionFactory sessionFactory;
#Autowired
public void setSessionFactory(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
public KeywordEntity findByKeyword(String keyword) throws NotFoundException {
Criteria criteria = sessionFactory.getCurrentSession()
.createCriteria(KeywordEntity.class)
.add(Restrictions.eq("keyword", keyword));
KeywordEntity entity = (KeywordEntity) criteria.uniqueResult();
if (entity == null) {
throw new NotFoundException("Not found");
}
return entity;
}
public KeywordEntity createKeyword(String keyword) {
KeywordEntity entity = new KeywordEntity(keyword);
save(entity);
return entity;
}
}
and a service, which puts everything under #Transactional:
#Repository
#Scope("prototype")
public class KeywordService {
#Autowired
private KeywordDao dao;
#Transactional(readOnly = true)
public KeywordEntity getKeyword(String keyword) throws NotFoundException {
return dao.findByKeyword(keyword);
}
#Transactional(readOnly = false)
public KeywordEntity createKeyword(String keyword) {
return dao.createKeyword(keyword);
}
#Transactional(readOnly = false)
public KeywordEntity getOrCreateKeyword(String keyword) {
try {
return getKeyword(keyword);
} catch (NotFoundException e) {
return createKeyword(keyword);
}
}
}
In a single-threaded environment this code runs just fine. The problems, when I use it in multi-threaded environment. When there are many parallel threads, working the same keywords, some of them are calling the getOrCreateKeyword with the same keyword at the same time and following scenario occurs:
2 threads at the same time call keyword service with the same keyword, both first tries to fetch the existing keyword, both are not finding, and both try to create new one. The first one succeeds, the second - causes ConstraintViolationException to be thrown.
So I did try to improve the getOrCreateKeyword method a little:
#Transactional(readOnly = false)
public KeywordEntity getOrCreateKeyword(String keyword) {
try {
return getKeyword(keyword);
} catch (NotFoundException e) {
try {
return createKeyword(keyword);
} catch (ConstraintViolationException ce) {
return getKeyword(keyword);
}
}
}
So theoretically it should solve the issues, but in practice, once ConstraintViolationException is thrown, calling the getKeyword(keyword) results in another Hibernate exception:
AssertionFailure - an assertion failure occured (this may indicate a bug in Hibernate,
but is more likely due to unsafe use of the session)org.hibernate.AssertionFailure:
null id in KeywordEntity entry (don't flush the Session after an exception occurs)
How to solve this problem?
You could use some sort of Pessimistic locking mechanism using the database/hibernate or you could make the service method getOrCreateKeyword() synchronized if you run on a single machine.
Here are some references.
Hibernates documentation http://docs.jboss.org/hibernate/core/3.3/reference/en/html/transactions.html#transactions-locking
This article shows how to put a lock on a specific entity and all entities from a result of a query which may help you.
http://www.objectdb.com/java/jpa/persistence/lock#Locking_during_Retrieval_
The solution was to discard the current session once ConstraintViolationException occurs and retrieve the keyword one more time within the new session. Hibernate Documentation also point to this:
If the Session throws an exception, the transaction must be rolled back and the session discarded. The internal state of the Session might not be consistent with the database after the exception occurs.