Handling a specific scenario with a Test to verify that it’s correctly implemented the Optimistic Lock

I’m tryng to get more into Optimistic Lock and in detail, verifyng with a test, that my implementation it’s correct. The implementation it’s with Java 11, SpringBoot and Maven interacting with a simple Sql DB.

The scenario i want to test it’s when, from two different applications, i’m tryng to update a single attribute ( handled with the @Version of jpa ) of the same entity record simultaneously. What i did was creating a simple project and do a test where in two different threads ( launched at the same time with a countdown ) i was mocking up two calls to different methods that update that attribute; I handled this services differently cause in one i just want to inform the user that the Object it’s already been updated, while in the other one i want to retry the update “n” times when i encounter that specific exception.

***For using the @Retryable i inserted in the pom this dependencyes:

<dependency>
            <groupId>org.springframework.retry</groupId>
            <artifactId>spring-retry</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
        </dependency>

and in the main this annotation : @EnableRetry***

This is the entity:

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
@Table(name="product")
public class ProductEntity {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="product_id")
    private Integer productId;
    
    @Column(name="name")
    private String name;
    
    @Column(name="version")
    @Version
    private Long version;
    
}

This is my controller:

@RestController
@RequestMapping("/api/product")
public class ProductAPIController {

    @Autowired
    private IProductService productService;
    

    @PutMapping("/new-name-one")
    public ResponseEntity<ProductDTO> updateProductOrFail( 
            @RequestBody @Valid ProductDTO productDTO)
            throws Exception {
        if(productDTO.getName() == null) {
            throw new ValidationException("The name has to be present");
        }
        try {
            ProductDTO updatedProduct = productService.updateProductOrFail(ProductDTO);
            return new ResponseEntity<ProductDTO>(updatedProduct, HttpStatus.OK);
        } catch (ObjectOptimisticLockingFailureException | OptimisticLockException e) {
            throw new OptimisticLockException("The Product has been updated by another transaction", e);
        }

    }
    
    
    @PutMapping("/new-name-two")
    public ResponseEntity<ProductDTO> updateProductOtherwiseRetry( 
            @RequestBody @Valid ProductDTO productDTO)
            throws Exception {
        if(productDTO.getName() == null) {
            throw new ValidationException("The name has to be present");
        }
        return new ResponseEntity<ProductDTO>(productService.updateProductOtherwiseRetry(productDTO), HttpStatus.OK);

    }```


I will skip the service Interface and go directly to the two methods inside the service:

@Service
public class ProductService implements IProductService {

@Autowired
ProductRepository productRepository;

@Autowired
ModelMapper modelMapper;


@Override
@Transactional
public ProductDTO updateProductOrFail(ProductDTO productDTO) throws ServiceException {
    ProductEntity product = productRepository.findById(productDTO.getProductId())
            .orElseThrow(() -> new ServiceException("Product not found"));
    product.setName(productDTO.getName());
    productRepository.save(product);
    return modelMapper.map(product, ProductDTO.class);
}

@Override
@Transactional
@Retryable(value = {OptimisticLockException.class,
                    OptimisticLockingFailureException.class,
                    ObjectOptimisticLockingFailureException.class},
            maxAttempts = 2, 
            backoff = @Backoff(delay = 1000))
public ProductDTO updateProductOtherwiseRetry(ProductDTO productDTO) throws ServiceException {
    ProductEntity product = userStoryRepository.findById(productDTO.getUserStoryId())
            .orElseThrow(() -> new ServiceException("Product not found"));
    product.setName(productDTO.getName());
    productRepository.save(product);
    //log.warn("The Product has been updated by another transaction try again...");
    return modelMapper.map(product, ProductDTO.class);
}



Inside my Controller class Test this is the implementation of the method:

@Test
void havingTwoConcurrencyThread_whenUpdatingTheNameOfAProduct_ThenOptimisticLockExceptionHasToBeThrown() throws Exception {
ProductEntity product = new ProductEntity();
product.setUserStoryId(null);
product.setName(“New Product”);
productRepository.save(product);

    CountDownLatch latch = new CountDownLatch(1);
    
    Thread t1 = new Thread(new Runnable() {
        @Override
        public void run() {
            ProductDTO productOneToUpdate = new ProductDTO();
            productOneToUpdate.setProductId(1);
            productOneToUpdate.setName("Product One");
           
            try {
                latch.await();
                log.info("Thread 1 has started...");
                MvcResult result = mockMvc.perform(MockMvcRequestBuilders.put(LINK + "/new-name-one")
                      .contentType(MediaType.APPLICATION_JSON)
                      .content(gson.toJson(productOneToUpdate)))
                      .andExpect(status().is2xxSuccessful()).andReturn();
                
                log.info("Thread 1 has performed the call");
                ProductDTO productChanged = gson.fromJson(result.getResponse().getContentAsString(), new TypeToken<ProductDTO>() {
                }.getType());
                
                assertEquals("Product One", productChanged.getName());
            }catch (Exception e){
                 log.error("Exception in Thread 1", e);
                
            }

        }
    });
    
    Thread t2 = new Thread(new Runnable() {
        @Override
        public void run() {
            
            ProductDTO productTwoToUpdate = new ProductDTO();
            productTwoToUpdate.setProductId(1);
            productTwoToUpdate.setName("Product Two");
            try {
                latch.await();
                log.info("Thread 2 has started...");
                mockMvc.perform(MockMvcRequestBuilders.put(LINK + "/new-name-two")
                          .contentType(MediaType.APPLICATION_JSON)
                          .content(gson.toJson(productTwoToUpdate)))
                          .andExpect(status().isConflict());
                
                log.info("Thread 2 has performed the call");
                
            } catch (Exception e) {
                log.error("Exception in Thread 2", e);
                 assertTrue(e.getCause() instanceof ObjectOptimisticLockingFailureException || 
                         e.getCause() instanceof OptimisticLockException);
            }
        }
    });
    
    t1.start();
    t2.start();
    
    latch.countDown();
    
    t1.join();
    t2.join();        
  }```

Maybe i didn’t give you enough sample code, but i can tell you that my project has succesfully been built, and inside my TestClass i have other test ( runned as Junit ) passed succesfully. When i run this test that’s the result of the console:

2024-06-13 18:19:33.669  INFO 29940 --- [       Thread-5] c.p.c.controller.ProductControllerIT   : Thread 2 has started...
2024-06-13 18:19:33.669  INFO 29940 --- [       Thread-4] c.p.c.controller.ProductControllerIT   : Thread 1 has started...
2024-06-13 18:19:33.887  INFO 29940 --- [       Thread-4] o.h.e.j.b.internal.AbstractBatchImpl     : HHH000010: On release of batch it still contained JDBC statements
2024-06-13 18:19:33.897 ERROR 29940 --- [       Thread-4] c.p.c.c.ControllerExceptionHandler       : Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1; statement executed: update product set name=?, version=? where product_id=? and version=?; nested exception is org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1; statement executed: update product set name=?, version=? where product_id=? and version=?

org.springframework.orm.ObjectOptimisticLockingFailureException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1; statement executed: update product set name=?, version=? where product_id=? and version=?; nested exception is org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1; statement executed: update product set name=?, version=? where product_id=? and version=?
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:318) ~[spring-orm-5.3.30.jar:5.3.30]
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:233) ~[spring-orm-5.3.30.jar:5.3.30]
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:566) ~[spring-orm-5.3.30.jar:5.3.30]
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:743) ~[spring-tx-5.3.30.jar:5.3.30]
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:711) ~[spring-tx-5.3.30.jar:5.3.30]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:654) ~[spring-tx-5.3.30.jar:5.3.30]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:407) ~[spring-tx-5.3.30.jar:5.3.30]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.30.jar:5.3.30]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.30.jar:5.3.30]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762) ~[spring-aop-5.3.30.jar:5.3.30]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:707) ~[spring-aop-5.3.30.jar:5.3.30]
    at com.example.project.service.ProductService$$EnhancerBySpringCGLIB$$******.updateProductOtherwiseRetry(<generated>) ~[classes/:na]
    at com.example.project.controller.ProductAPIController.updateProductOrFail(ProductAPIController.java:80) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na] [...]

Caused by: org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1; statement executed: update product set name=?, version=? where product_id=? and version=?
    at org.hibernate.jdbc.Expectations$BasicExpectation.checkBatched(Expectations.java:67) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.jdbc.Expectations$BasicExpectation.verifyOutcome(Expectations.java:54) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:47) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3571) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:3438) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3870) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.action.internal.EntityUpdateAction.execute(EntityUpdateAction.java:202) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:478) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:684) ~[na:na]
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:475) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:344) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:40) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1407) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:489) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3303) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2438) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:449) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:183) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$300(JdbcResourceLocalTransactionCoordinatorImpl.java:40) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:281) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:101) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:562) ~[spring-orm-5.3.30.jar:5.3.30]
    ... 82 common frames omitted



Exception in thread "Thread-4" Exception in thread "Thread-5" java.lang.AssertionError: Range for response status value 500 expected:<SUCCESSFUL> but was:<SERVER_ERROR>
    at org.springframework.test.util.AssertionErrors.fail(AssertionErrors.java:59)
    at org.springframework.test.util.AssertionErrors.assertEquals(AssertionErrors.java:122)
    at org.springframework.test.web.servlet.result.StatusResultMatchers.lambda$is2xxSuccessful$3(StatusResultMatchers.java:78)
    at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:214)
    at com.example.project.controller.ProductyControllerIT$5.run(ProductControllerIT.java:476)
    at java.base/java.lang.Thread.run(Thread.java:834)
java.lang.AssertionError: Status expected:<409> but was:<200>
    at org.springframework.test.util.AssertionErrors.fail(AssertionErrors.java:59)
    at org.springframework.test.util.AssertionErrors.assertEquals(AssertionErrors.java:122)
    at org.springframework.test.web.servlet.result.StatusResultMatchers.lambda$matcher$9(StatusResultMatchers.java:627)
    at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:214)
    at com.example.project.controller.ProductyControllerIT$6.run(ProductControllerIT.java:504)
    at java.base/java.lang.Thread.run(Thread.java:834)
2024-06-13 18:19:33.987  INFO 29940 --- [ionShutdownHook] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2024-06-13 18:19:33.988  INFO 29940 --- [ionShutdownHook] .SchemaDropperImpl$DelayedDropActionImpl : HHH000477: Starting delayed evictData of schema as part of SessionFactory shut-down'
2024-06-13 18:19:33.997  INFO 29940 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2024-06-13 18:19:34.004  INFO 29940 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

The first mock up call in the first thread it’s the call to the services that has the @Retryable annotation so i expect that that’s the one that has to be retryed and give me a 200, while the second one it’s the one that should fail.
What i read from the console is that the assertion i have in the first one failed, and give me a 500 Code, while the second one succeeded instead of giving me a Conflict Code.

I don’t know if my Test it’s formally correct and cover the test case where, with two concurrent transaction, i can let prevail the one i want. I also am not completely sure if that’s how someone has to implement correctly the Optimistick Lock. There are a lot of things that i have to learn, but i just wanted to get my hands dirty and tryng to implement it.

Also, how can i correctly verify if this works or not?

  • java
  • spring
  • optimistic-locking

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