Getting "javax.persistence.TransactionRequiredException: no transaction is in progress" in Spring Boot Application

I am using JPA+Hibernate in my Spring Boot Application. My Service Method is as follows:-

    @Override
	public Employee createEmployee(Employee employeeModel) {
		logger.debug("entered the createEmployee method");
		Optional<Employee> optionalEmployee = repository.findByEmpShortNm(employeeModel.getEmpShortNm());
		logger.debug("Fetched the optional");
		if(optionalEmployee.isPresent())
			return optionalEmployee.get();
		else {
			logger.debug("Persisting employee.....");
			return repository.save(employeeModel);
		}
	}

EmployeeRepository.java has following method:-

@Lock(LockModeType.PESSIMISTIC_WRITE)
Optional<Employee> findByEmpShortNm(String uuid);

My Application was working fine until I applied Lock annotation on my repository method. After applying Lock createEmployee method is throwing following exception:-

javax.persistence.TransactionRequiredException: no transaction is in progress
at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1560)
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1533)
at org.hibernate.query.internal.AbstractProducedQuery.getSingleResult(AbstractProducedQuery.java:1581)
at org.hibernate.query.criteria.internal.compile.CriteriaQueryTypeQueryAdapter.getSingleResult(CriteriaQueryTypeQueryAdapter.java:111)
at org.springframework.data.jpa.repository.query.JpaQueryExecution$SingleEntityExecution.doExecute(JpaQueryExecution.java:196)
at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:88)
at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:154)
at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:142)
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor$QueryMethodInvoker.invoke(QueryExecutorMethodInterceptor.java:195)
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:152)
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:130)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)

Why it's not able to get a transaction while it was working fine when I was not using @Lock Annoation. What's the relation b/w @Lock and Transaction.

I would appreciate if any reference can be provided.

Solution: you should annotate your service with @Transactional

> When the lock is explicitly enabled and there is no active
> transaction, the underlying JPA implementation will throw a
> TransactionRequiredException.

It is somehow logical when you don't have your own transaction, why do you want to lock the entity object? You should have a transaction outside repository method during which, you want to lock entity object.

Read this article:

https://www.baeldung.com/java-jpa-transaction-locks