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1. Overview

This tutorial will discuss the right way to configure Spring Transactions, how to use the @Transactional annotation and common pitfalls.

For a more in-depth discussion on the core persistence configuration, check out the Spring with JPA tutorial.

There are two distinct ways to configure Transactions – annotations and AOP – each with their own advantages – we’re going to discuss the more common annotation-config here.

2. Configure Transactions without XML

Spring 3.1 introduces the @EnableTransactionManagement annotation to be used in on @Configuration classes and enable transactional support:

@Configuration
@EnableTransactionManagement
public class PersistenceJPAConfig{

   @Bean
   public LocalContainerEntityManagerFactoryBean
     entityManagerFactoryBean(){
      //...
   }

   @Bean
   public PlatformTransactionManager transactionManager(){
      JpaTransactionManager transactionManager
        = new JpaTransactionManager();
      transactionManager.setEntityManagerFactory(
        entityManagerFactoryBean().getObject() );
      return transactionManager;
   }
}

3. Configure Transactions with XML

Before 3.1 or if Java is not an option, here is the XML configuration, using annotation-driven and the namespace support:

<bean id="txManager" class="org.springframework.orm.jpa.JpaTransactionManager">
   <property name="entityManagerFactory" ref="myEmf" />
</bean>
<tx:annotation-driven transaction-manager="txManager" />

4. The @Transactional Annotation

With transactions configured, a bean can now be annotated with @Transactional either at the class or method level:

@Service
@Transactional
public class FooService {
    //...
}

The annotation supports further configuration as well:

  • the Propagation Type of the transaction
  • the Isolation Level of the transaction
  • a Timeout for the operation wrapped by the transaction
  • a readOnly flag – a hint for the persistence provider that the transaction should be read only
  • the Rollback rules for the transaction

Note that – by default, rollback happens for runtime, unchecked exceptions only. The checked exception does not trigger a rollback of the transaction; the behavior can, of course, be configured with the rollbackFor and noRollbackFor annotation parameters.

5. Potential Pitfalls

5.1. Transactions and Proxies

At a high level, Spring creates proxies for all the classes annotated with @Transactional – either on the class or on any of the methods. The proxy allows the framework to inject transactional logic before and after the method being invoked – mainly for starting and committing the transaction.

What is important to keep in mind is that, if the transactional bean is implementing an interface, by default the proxy will be a Java Dynamic Proxy. This means that only external method calls that come in through the proxy will be intercepted – any self-invocation calls will not start any transaction – even if the method is annotated with @Transactional.

Another caveat of using proxies is that only public methods should be annotated with @Transactional – methods of any other visibilities will simply ignore the annotation silently as these are not proxied.

This article discusses further proxying pitfalls in great detail here.

5.2. Changing the Isolation level

You can change transaction isolation level – as follows:

@Transactional(isolation = Isolation.SERIALIZABLE)

Note that this has actually been introduced in Spring 4.1; if we run the above example before Spring 4.1, it will result in:

org.springframework.transaction.InvalidIsolationLevelException: Standard JPA does not support custom isolation levels – use a special JpaDialect for your JPA implementation

5.3. Read-Only Transactions

The readOnly flag usually generates confusion, especially when working with JPA; from the Javadoc:

This just serves as a hint for the actual transaction subsystem; it will not necessarily cause failure of write access attempts. A transaction manager which cannot interpret the read-only hint will not throw an exception when asked for a read-only transaction.

The fact is that it cannot be guaranteed that an insert or update will not occur when the readOnly flag is set – its behavior is vendor dependent whereas JPA is vendor agnostic.

It is also important to understand that the readOnly flag is only relevant inside a transaction; if an operation occurs outside of a transactional context, the flag is simply ignored. A simple example of that would call a method annotated with:

@Transactional( propagation = Propagation.SUPPORTS,readOnly = true )

from a non-transactional context – a transaction will not be created and the readOnly flag will be ignored.

5.4. Transaction Logging

Transactional related issues can also be better understood by fine-tuning logging in the transactional packages; the relevant package in Spring is “org.springframework.transaction”, which should be configured with a logging level of TRACE.

6. Conclusion

We covered the basic configuration of transactional semantics using both java and XML, how to use @Transactional and best practices of a Transactional Strategy. The Spring support for transactional testing as well as some common JPA pitfalls was also discussed.

As always, the code presented in this article is available over on Github. This is a Maven based project, so it should be easy to import and run as it is.

I usually post about Persistence on Twitter - you can follow me there:


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Łukasz Bachman
Guest

Nice one here, my friend. I wanted to dig into transaction management for a long time and this is great post to help me get started Thanks!

Russell
Guest

Nice one. Very useful. One important question. How to change default transaction isolation level in JPA/Hibernate environment. The “hibernate.connection.isolation” only works if you use DriverManager which is not a option in most JEE container.

Eugen Paraschiv
Guest

Yeah, isolation has always been a bit of a problem with JPA – I’ve seen solutions that were doing low level hacks in the JDBC Driver but nothing that worked well unfortunately.

Rahul
Guest

Getting the exception:

javax.persistence.TransactionRequiredException: no transaction is in progress
at org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:959) ~[hibernate-entitymanager-3.6.10.Final.jar:3.6.10.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.6.0_21]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) ~[na:1.6.0_21]

I have used @Transactional at DAO layer but still getting this error.

Eugen Paraschiv
Guest

Hi Rahul,
Sorry for the late reply – if you’re seeing problems with the example project on github, please raise an issue over there and I’ll take a look at the problem.
Cheers,
Eugen.

Emanuele Ianni
Guest

Hi! Is there a way to share a common superclass among different PersistenceJPAConfig subclasses? My use case is I have 3 different datasource, right now I have to redefine the Bean transactionManager() in each subclass so that the transaction is open. If I leave that method on the superclass flush won’t work because no transaction is active. Thank you very much.

Eugen Paraschiv
Guest

You can use the @ImportResource for this – please see this as an example..

Thiruppathy.R
Guest

Very Useful. Thank you!

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