I'm working on a bunch of legacy code written by people before me and I'm confused about a particular kind of setup and wonder if this has ever worked to begin with.
There is a managed bean in spring that has a transactional method.
#Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = Throwable.class)
public boolean updateDraftAndLivePublicationUsingFastDocumentsOfMySite(List<FastDocumentLite> fastDocumentLites, Long mySiteId) throws Exception { ... }
Now inside that method I find new instantiations calling update methods fe:
boolean firstFeed = new MySiteIdUpdate(publishing, siteDao, siteDomainService).update(siteId, fastDocumentLites.get(0).getMySiteId());
From my understanding on IOC this new class isn't managed by spring , it's just a variable in the bean. Now going further inside the update method you see another service gets called.
#Transactional(propagation=Propagation.REQUIRED, rollbackFor=Throwable.class)
public void activateSubdomainForSite(Long siteId, boolean activationOfSite)
So if there is a transaction open it should be propagated into this service. But here is what I don't get if that MySiteIdUpdate object isn't managed by spring does the first transaction move forward to the activateSubdomainForSite method ?? Or is another transaction being opened here. I looked in the logs and I believe it to be the latter but I rather ask the experts for a second oppinion before I proclame this legacy code to be complete rubbish to the project lead. I'm suffering with a StaleStateException somewhere further down the road and I'm hoping this has anything to do with it.
I think the code is correct, and the second #Transactional should reuse the existing transaction.
Because:
1) Spring Transaction handling is done either by Proxies or by AspectJ advices. If it is done by Proxies then it is required that MySiteIdUpdate invoke an instance that is injected (this is what you did). If you use AspectJ, then it should work anyway.
2) The association Transactions to the code that use is done by the Thread, this mean, as long as you "are" in the thread which started the transaction you can use it. (you do not start an new thread, so it should work)
An other way to explain: It is perfect legal when you have some method in your call hierarchy that does not belong to an spring bean. This should not make the transaction handling fail.
Related
I am trying to understand a project which involves spring's declarative transactional annotation. The body of the function is not making any JDBC calls or calling JPA repository methods. All it is doing is call some third party API and transform it's results, it's not even saving the response in the database. So no database interactions at all.
My question is that is it worth using #Transactional annotation on this method? Because as per my understanding #Transactional only helps in maintaining consistency in databases.
The #Transactional annotation defines the scope of a single database transaction - all it does is it begins the transaction and either commit it or rollback. It allows to manage transaction declarative way rather than do it programatically every time.
It looks something like this:
UserTransaction utx = entityManager.getTransaction();
try {
utx.begin();
// your method invocation here
utx.commit();
} catch(RuntimeException ex) {
utx.rollback();
throw ex;
}
By making method #Transactional when there is no database calls you only make its performance worse as redundant steps have to take place when not necessary.
<prop key="load*">PROPAGATION_REQUIRED, readOnly</prop>
Here the key="load*" uses wildcard "*". It matches every function that starts with load right? My question is that; how am I going to implement this using annotation based configuration without placing it on every function?
#Transactional(readOnly = true, propagation= Propagation.REQUIRED)
Is there anyway I can do this without putting this on top of every function which it's name starts with "load"?
Cheers
You can use aspects for this purpose. I.e. define an aspect which intercepts all methods named as "load*" and ensure transaction is started. However in my opinion, such approach is a bad one since it makes your code hard to unit test, understand and maintain further. In fact #Transactional handling is done using aspects, so why bothering to add another layer of abstraction to this? With this annotation someone will look to your code and immediately know that method is/should be running in transaction. Hiding this will make others life harder.
If you still want to implement it, here is small example. NOTE, that I didn't test this at all, just an idea demonstration.
#Aspect
public class MyInterceptor
{
#Around("execution(* load*(..))")
#Transactional
public Object makeMeTransactional(ProceedingJoinPoint pjp)
{
return pjp.proceed();
}
}
I've built some code that can rebuild expression trees so I can avoid triggering the no supported translation to SQL exception and it works fine as long as I call my function to replace the iqueryable. The problem is that I'd like it to automatically be applied to all queries in my project without having to worry about calling this function on each one separately. Is there any way that I can intercept everything?
I've tried using Reflection.Emit to create a wrapping provider and using reflection to replace it on the data context and it turns out that even with Reflection.Emit I can't implement the internal IProvider interface.
I've also tried replacing the provider with a RealProxy based class and that works for non-compiled queries, but the CompiledQuery.Execute method is throwing an exception because it won't cast to the SqlProvider class. I tried replacing the response to the Compile method on the provider with another proxy so I could intercept the Execute call, but that failed a check on the return type being correct.
I'm open to any other ideas or ways of using what I've already tried?
It's hard to tell whether this is an applicable solution without seeing your code, but if you have a DI-friendly app architecture you can implement an interceptor and have your favorite IoC container emit the appropriate type for you, at run-time.
Esoteric? A little. Consider an interface like this:
public interface ISomeService
{
IEnumerable<SomeEntity> GetSomeEntities();
// ...
}
This interface might be implemented like this:
public class SomeService : ISomeService
{
private readonly DbContext _context // this is a dependency!
private readonly IQueryTweaker _tweaker; // this is a dependency!
public SomeService(DbContext context, IQueryTweaker tweaker) // this is constructor injection!
{
_context = context;
_tweaker = tweaker;
}
public IEnumerable<SomeEntity> GetSomeEntities()
{
return _tweaker.TweakTheQuery(_context.SomeEntities).ToList();
}
}
Every time you implement a method of the ISomeService interface, there's always a call to _tweaker.TweakTheQuery() that wraps the IQueryable, and that not only gets boring, it also feels like something is missing a feature - the same feeling you'd get by wrapping every one of these calls inside a try/catch block, or if you're familiar with MVVM in WPF, by raising this annoying PropertyChanged event for every single property setter in your ViewModel.
With DI Interception, you factor this requirement out of your "normal" code and into an "interceptor": you basically tell the IoC container that instead of binding ISomeService directly to the SomeService implementation, you're going to be decorating it with an interceptor, and emit another type, perhaps SomeInterceptedService (the name is irrelevant, the actual type only exists at run-time) which "injects" the desired behavior into the desired methods. Simple? Not exactly.
If you haven't designed your code with DI in mind (are your dependencies "injected" into your classes' constructor?), it could mean a major refactoring.
The first step breaks your code: remove the IQueryTweaker dependency and all the TweakTheQuery calls from all ISomeService implementations, to make them look like this - notice the virtualness of the method to be intercepted:
public class SomeService : ISomeService
{
private readonly DbContext _context
public SomeService(DbContext context)
{
_context = context;
}
public virtual IEnumerable<SomeEntity> GetSomeEntities()
{
return _context.SomeEntities.ToList();
}
}
The next step is to configure the IoC container so that it knows to inject the SomeService implementation whenever a type's constructor requires an ISomeService:
_kernel.Bind<ISomeService>().To<SomeService>();
At that point you're ready to configure the interception - if using Ninject this could help.
But before jumping into that rabbit's hole you should read this article which shows how decorator and interceptor are related.
The key point is, you're not intercepting anything that's internal to LINQ to SQL or the .NET framework itself - you're intercepting your own method calls, wrapping them with your own code, and with a little bit of help from any decent IoC container, you'll be intercepting the calls to methods that call upon Linq to SQL, rather than the direct calls to Linq to SQL itself. Essentially the IQueryTweaker dependency becomes a dependency of your interceptor class, and you'll only code its usage once.
An interesting thing about DI interception, is that interceptors can be combined, so you can have a ExecutionTimerServiceInterceptor on top of a AuditServiceInterceptor, on top of a CircuitBreakerServiceInterceptor... and the best part is that you can configure your IoC container so that you can completely forget it exists and, as you add more service classes to the application, all you need to do is follow a naming convention you've defined and voilà, you've just written a service that not only accomplishes all the strictly data-related tasks you've just coded, but also a service that will disable itself for 3 minutes if the database server is down, and will remain disabled until it's back up; that service also logs all inserts, updates and deletes, and stores its execution time in a database for performance analysis. The term automagical seems appropriate.
This technique - interception - can be used to address cross-cutting concerns; another way to address those is through AOP, although some articles (and Mark Seeman's excellent Dependency Injection in .NET) clearly demonstrate how AOP frameworks are a less ideal solution over DI interception.
I'm a beginner in hibernate 4 & Spring 3.2 stuffs.
I have read some tutorials and discussion on stack but i don't find a clear answer to my questions. And i think the best way to understand is to ask and share knowledges !
Here we go!
So you create each time a Pojo, a Dao , a Service class, with methods annotated transactionnal. That's ok. I'm using Sessionfactory to handle my transaction. I'm looking for good practices.
1- If you want to use Delete Method and Save Method from the same Service, how will you do to make it works in a same transaction. When i look at the log, each method are executed in different transactions.
This SampleServiceImpl:
#Transactional
public void save(Sample sample){
sampleDao.save(sample);
}
#Transactional
public void delete(Sample sample){
sampleDao.delete(sample);
}
// A solution could be that , but not very clean...there should be an another way, no?
#Transactional
public void action(Sample sample){
sampleDao.save(sample);
sampleDao.delete(sample);
}
2- If you want to use Delete Method and Save Method from different Services class, how will you do to make it works in a same transaction. Because each method in each service class is handled by a Transactionnal annotation. Do you create a global Service calling all subservice in one method annoted Transactional
SampleServiceImpl:
#Transactional
public void save(Sample sample){
sampleDao.save(sample);
}
ParcicipantServiceImpl
#Transactional
public void save(Participant participant){
participantDao.save(participant);
}
// A solution could be that , but not very clean...there should be an another way, no?
GlobalServiceImpl
#Transactional
public void save(Participant participant,Sample sample){
participantDao.save(participant);
sampleDao.save(sample);
}
3- And the last question but not the least .If you want to use several Methods from severals service in one global transaction. Imagine you want to fill up 5 or more table in one execution of a standalone program. How is it possible because each Service to have his proper transactional method, so each time you called this method, there is a transaction.
a- I have successfully arrive to fill up two tables in a sample transaction using Mkyong tutorial and cascade property in the mapping. So i see how to make it works for one table directly joined to one another or more tables.
b- But if you have a 3 tables Participant -> Samples -> Derived Products. How will you fill up the three tables in a same transaction.
I don't know if i'm clear. But i would appreciated some help or example on that from advanced users.
Thanks a lot for you time.
Your solution is fine, maybe this works if you want to using nested transactional methods(note I saw this solution couple days ago and didn't test it):
< tx:annotation-driven mode="aspectj" / >
< context:load-time-weaver aspectj-weaving="on"/ >
#Transactional
public void action(Sample sample){
save(sample);
delete(sample);
}
Transaction should propagate.
GlobalServiceImpl
#Transactional
public void save(Participant participant,Sample sample){
participantDao.save(participant);
sampleServiceImpl.save(sample);
}
The approch you are following is cleaner approch,
ServiceOpjects are ment to contain business logic. Hence they will always manuplate through data objects.
What we do in practise is create a another layer that uses dataObjects and and other functional call of same layer. Then this all business layer is called via service layer having annotation #transactional.
Can you please mention why you think this approch is dirty??
I am using Spring 3, JPA + Hibernate for a CMS application. In that application I have a service class method which is annotated with #Transactional Annotation with rollBack property. Inside that method I am inserting data (ie entity classes) to a table using a loop. For each iteration of the loop entity classes has to be saved to the database. But it is not happening. The commit only happens when the execution of the loop has completed and exits from the method. Then it commits and saves all at once. But I need to read data once it gets inserted into the database before committing in this case. I tried with the ISOLATION LEVEL to read uncommitted but it didn't supported since I am using the default JPADialect. Also tried to add the hibernate implementation of jpaDialect but still it didn't worked. Please help with a workaround for this problem. One more thing, is there any way using propagation required method.
You are right, this is what I stands for in acid. Because the transactions are working in isolation, other transactions cannot see them before they are committed. But playing with isolation levels is a bad practice. I would rather advice you to run each and every iteration in a separate transaction with start and commit inside.
This is a bit tricky in Spring, but here is an example:
public void batch() {
for(...) {
insert(...)
}
}
//necessarily in a different class!
#Transactional
public void insert() {
}
Note that batch() is not annotated with #Transactional and insert() has to be in a different class (Spring service). Too long to comment, but that's life. If you don't like it, you can use TransactionTemplate manually.
remove the transactional annoation on the the method with loop.
In the loop call a separate method to perform the save, make that method transactional
You either need to go with programmatic transactions (Spring's TransactionTemplate or PlatformTransactionManager are the classes to look at, see Spring Doc for programmatic transactions, or you can call another transactional method from within your loop where the transaction is marked with Propagation.REQUIRES_NEW, meaning each call of that method is executed in its own transaction, see here. I think that the second approach requires you to define the REQUIRES_NEW method on a different Spring bean because of the AOP-Proxy. You can also omit the REQUIRES_NEW if the loop is not executed within a transaction.