What is the use of @transactional in Spring?
The @Transactional annotation makes use of the attributes rollbackFor or rollbackForClassName to rollback the transactions, and the attributes noRollbackFor or noRollbackForClassName to avoid rollback on listed exceptions. The default rollback behavior in the declarative approach will rollback on runtime exceptions.
What is the purpose of @transactional annotation?
Transactional annotation provides the application the ability to declaratively control transaction boundaries on CDI managed beans, as well as classes defined as managed beans by the Java EE specification, at both the class and method level where method level annotations override those at the class level.
When should I use @transactional?
What Is @Transactional? We can use @Transactional to wrap a method in a database transaction. It allows us to set propagation, isolation, timeout, read-only, and rollback conditions for our transaction. We can also specify the transaction manager.
Do we need @transactional in Spring boot?
If you're using Spring without Spring Boot, you need to activate the transaction management by annotating your application class with @EnableTransactionManagement. Here you can see a simple example of a service with a transactional method.
Is @transactional mandatory?
@Transactional(MANDATORY) : fails if no transaction was started ; works within the existing transaction otherwise. @Transactional(SUPPORTS) : if a transaction was started, joins it ; otherwise works with no transaction.
Can we use @transactional in repository?
The usage of the @Repository annotation or @Transactional . @Repository is not needed at all as the interface you declare will be backed by a proxy the Spring Data infrastructure creates and activates exception translation for anyway.
What is @transactional in Spring boot?
The @Transactional annotation is metadata that specifies that an interface, class, or method must have transactional semantics; for example, "start a brand new read-only transaction when this method is invoked, suspending any existing transaction".
What is the main purpose of transaction?
A transaction is a completed agreement between a buyer and a seller to exchange goods, services, or financial assets in return for money. The term is also commonly used in corporate accounting.
Can we use transactional in async?
In order to make Spring manage the transaction of the @Async method either the @Component or the method itself should declare the @Transactional annotation, this way Spring will manage the transaction even if a method is being executed asynchronous.
Why is @transactional used in service?
The @Transactional annotation belongs to the Service layer because it is the Service layer's responsibility to define the transaction boundaries.
What happens if we dont use @transactional?
Hard to use the database to troubleshoot test failures Another problem with using @Transactional is that you can't use the database to investigate the failure reasons, as the data is never actually saved into the database because transactions are always rollback'd at the end of the test method execution.
Can we add @transactional for private method?
As most of you probably know, due to the very nature of the solution, Spring's @Transactional annotation does not work on private methods unless you're using the AspectJ mode (which, in my experience, most of us aren't).
What is the purpose of transactional text?
Transactional writing is non-fiction writing that intends to communicate information between individuals or groups. Non-fiction texts include (amongst others): magazine articles. travel writing.
What is the main purpose of transaction?
A transaction is a completed agreement between a buyer and a seller to exchange goods, services, or financial assets in return for money. The term is also commonly used in corporate accounting.
What is the purpose of transaction design?
Usually this kind of design is done for administration transactions. When your are hitting several hundreds of TPS, you must design transactions for ensure performance and reliability first. For instance, all the new and delete stuff and memory copies should be avoided at all costs.
What is @transactional annotation in Spring MVC?
The @Transactional annotation is metadata that specifies that an interface, class, or method must have transactional semantics; for example, "start a brand new read-only transaction when this method is invoked, suspending any existing transaction".
What does readonly=true do?
readOnly=true can trigger a few performance optimizations in the underlying entity manager such as skipping dirty checks when closing the EntityManager via setting the FlushMode to MANUAL
What is a boolean flag?
A boolean flag served as a hint for the actual transaction subsystems
What is the default and most practical option?
The default and most practical option is Propagation.REQUIRED
What are the options for isolation level?
You can declare which isolation level you'd like to use with this property. The options are DEFAULT, READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE
What is @transacional annotation?
In Spring, @Transacional annotation is used for indicating a method run inside a database transaction. It can also be annotated on the class level which applies as a default to all methods of the declaring class and its subclasses
Is a transaction rollbacked by throwing my exception?
Then the transaction is not rollbacked by the throwing MyException as expected
Is there a redundant JPA call?
There are no redundant JPA calls to the database. However, you may encounter an issue like the following example which might not work as expected
Why do we use @Transactional annotation?
We also use @Transactional annotation to lock the record so that another thread/request would not change the read.
What is the meaning of "back up"?
Making statements based on opinion; back them up with references or personal experience.
Can annotations be reduced on the data access layer?
I think that the question is a little bit wider and cannot be reduced on the annotations on the data access layer. We need to consider the entire stack of the application, the transaction strategies we want to apply and so on. There is a very comprehensive set of articles on this topic by Mark Richards on IBM developerworks site. You can find the first one here: https://developer.ibm.com/articles/j-ts1/
Can @transactional be used for query methods?
Thus we recommend using @Transactional (readOnly = true) for query methods as well which you can easily achieve adding that annotation to you repository interface. Make sure you add a plain @Transactional to the manipulating methods you might have declared or re-decorated in that interface.
Is @transactional required in Spring Data?
I noticed that the use of @Transactional isn't required when you're using spring-data since I also tried my queries without the annotation.
What is declarative transaction?
Declarative transactions separates transaction management code from the business logic. Spring supports declarative transactions using transaction advice (using AOP) via XML configuration in the spring context or with @Transactional annotation.
What is proxy in Spring?
A proxy provides a way for Spring to inject behaviors before, after, or around method calls into the object being proxied. Internally, its the same as using a transaction advice (using AOP), where a proxy is created first and is invoked before/after the target bean’s method.
What is read uncommitted?
Read Uncommitted – Allows dirty reads, when a transaction is not yet committed by a thread and another thread is reading the dirty data.
Why is transaction management code written?
With programmatic transactions, transaction management code needs to be explicitly written so as to commit when everything is successful and rolling back if anything goes wrong. The transaction management code is tightly bound to the business logic in this case.
What is repeatable read?
Repeatable Read – If the same data is read twice in the same transaction, it will always be the same. This level guarantees that any data once read cannot change. Serializable – Transactions occur with locking at all levels (read, range and write locking), because of which they are executed in a fixed sequence.
What is repeatable read isolation?
With the Repeatable Read isolation level, the state of the database is maintained from the start of the transaction. If you retrieve a value in session1, then update that value in session2, retrieving it again in session1 will return the same results.
Is it better to specify readonly or readonly?
Its always better to explicitly specify the readOnly attribute, as we have noticed some massive performance improvements with Hibernate because of this.
2. Handling not all exceptions
By default, a rollback occurs only on RuntimeException and Error. At the same time, the code may contain checked exceptions, in which it is also necessary to roll back the transaction.
3. Transaction isolation levels and propagation
Often, developers add annotations without really thinking about what kind of behavior they want to achieve. The default isolation level READ_COMMITED is almost always used.
4. Transactions do not lock data
Sometimes there is a construction when we select something in the database, then update it, and think that since all this is done in a transaction and transactions have atomicity property, this code is executed as a single request.
5. Two different data sources
For example, we have created a new version of the datastore but still have to maintain the old one for a while.
Conclusion
Transactions are a tricky topic, and there can often be problems in knowledge. Most of the time, they are not fully covered by tests, so that most mistakes can be noticed only in the code review. And if incidents happen in production, finding a root cause is always a challenge.
