I am migrating an EJB project to Spring boot project. I have successfully replaced other annotations to the spring annotation, but havving problem with SessionContext object.
My legacy code is bellow
#Resource
SessionContext sessionContext;
.....
if (some condition) {
sessionContext.setRollbackOnly();
return false;
}
For this code i am getting the following error
A component required a bean of type 'javax.ejb.SessionContext' that could not be found.
Action:
Consider defining a bean of type 'javax.ejb.SessionContext' in your configuration.
I think you'll have to use a few different functionalities.
setRollbackOnly()
Most often I have seen Session Context used for Rollbacks. In Spring, you can replace this with:
TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
or annotate class with
#Transactional(rollbackFor = MyException.class)
so you can throw your exception from class to cause rollback.
getBusinessObject()
The second most commonly used feature is method to load a business object so that I can, for example, create a new transaction within a same bean. In this case you can use Self-inject:
#Lazy private final AccountService self;
and annote method with #Transactional. This, of course, solves any other cases where you need to use the power of a proxy object.
Other functionality is provided by other classes in Spring, but I think that these two are the most commonly used in the Java EE world and when migrating, one will look to replace them in Spring.
Related
Title speaks for itself.
Is PersistenceExceptionTranslationPostProcessor used solely for JPA implementations or is it relevant to use it with Spring's JdbcTemplate too?
And if there are two datasources needed each with their own JPA entity manager and transaction manager, do I still only need to specify one PersistenceExceptionTranslationPostProcessor for the entire application?
The auto-award bounty answer is wrong
~~~The correct answer is as follows~~~
I believe I've discovered the answer here:
http://www.deroneriksson.com/tutorials/java/spring/introduction-to-the-spring-framework/component-scanning-and-repository
The #Repository annotation can have a special role when it comes to converting exceptions to Spring-based unchecked exceptions. Recall that the JdbcTemplate handled this task for us. When we work with Hibernate, we’re not going to work with a Spring template that handles this conversion of Hibernate-based exceptions to Spring-based exceptions. As a result, in order to handle this conversion automatically, Hibernate DAOs annotated with #Repository will have their Hibernate exceptions rethrown as Spring exceptions using a PersistenceExceptionTranslationPostProcessor.
Further reading: http://www.deroneriksson.com/tutorials/java/spring/introduction-to-the-spring-framework/hibernate-daos
The paragraph above explicitly says:
Recall that the JdbcTemplate handled this task for us
So, to answer my own question, there is no need to use PersistenceExceptionTranslationPostProcessor with jdbcTemplate
Yes you can, The Spring exception translation mechanism can be applied transparently to all beans annotated with #Repository – by defining an exception translation bean post processor bean in the Context:
<bean id="persistenceExceptionTranslationPostProcessor"
class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />
As per it doc
Bean post-processor that automatically applies persistence exception translation to any bean marked with Spring's #Repository
annotation, adding a corresponding
PersistenceExceptionTranslationAdvisor to the exposed proxy (either an
existing AOP proxy or a newly generated proxy that implements all of
the target's interfaces).
Translates native resource exceptions to Spring's DataAccessException hierarchy. Autodetects beans that implement the
PersistenceExceptionTranslator interface, which are subsequently asked
to translate candidate exceptions.
All of Spring's applicable resource factories (e.g. LocalContainerEntityManagerFactoryBean) implement the
PersistenceExceptionTranslator interface out of the box. As a
consequence, all that is usually needed to enable automatic exception
translation is marking all affected beans (such as Repositories or
DAOs) with the #Repository annotation, along with defining this
post-processor as a bean in the application context.
So you can use it with Jdbctemplate as well as with any Jpa vendor implementation
As per is doc All of Spring's applicable resource factories (e.g. LocalContainerEntityManagerFactoryBean) implement the PersistenceExceptionTranslator interface out of the box, I think you still need to use PersistenceExceptionTranslationPostProcessor, because it used to translate all errors generated during the persistence process (HibernateExceptions, PersistenceExceptions...) into DataAccessException objects.
I have a third party jar in my class path which has some services and DAO's developed on top of Spring 2.0.6 and Hibernate3.2.6. I need to call some of the services and daos.
Using ClassPathXmlApplicationContext I'm able to load the application context and able to access the services and daos. Both the service and dao are following ProxyFactoryBean pattern.
Problem comes when I'm accessing a DAO which has some single valued associations.When I'm accessing associated entity I'm getting lazy initialization problem.
To solve this problem:- If it is in my own application JAR I'll be able to change the fetch type into join or in DAOImpl method I could use Hibernate.initialize().
Is there a way to avoid this problem from the stand alone code itself? Or any other way to solve this issue without modifying applicationContext.xml and DAOImpl
You need to put the caller method into one single transaction.
If you have Spring transactional environment, you can put the call of the DAO services/repositories in your own service/method which is marked as #Transactional, or if transaction support is not enabled, but you still have spring support in your application, you can just use TransactionTemplate directly, provided by spring
#Autowire
private PlatformTransactionManager txManager;
TransactionTemplate template = new TransactionTemplate(this.txManager);
template.execute( new TransactionCallback<Object>(){
public void doInTransaction(TransactionStatus status){
// work done here will be wrapped by a transaction and committed.
// status.setRollbackOnly(true) is called or an exception is thrown
}
});
Otherwise you have manually handle transactionality by your own , depending on the technologies your app is using.
I'm currently trying to configure Spring Boot (using Java Annotations and ComponentScan) for the following scenario:
Scenario
There's an interface MyService.
I want to provide a default implementation for MyService, let's call it MyDefaultService.
If the component scan detects no other implementation for MyService, Spring should instantiate MyDefaultService as a "fallback".
If there is a different implementation of MyService present, let's say MyCustomService, then that bean should always take precedence over MyDefaultService when autowiring a dependency to MyService. In that regard, MyDefaultService should be recessive (as opposed to #Primary).
Ideally, there should not need to be an additional annotation on MyCustomService to have it "override" MyDefaultService.
Ideally, no explicitly implemented factories or factory methods should be required.
Question
The question is: how do I need to annotate the MyDefaultService class in order to achieve this?
What I tried so far to solve the problem
Annotating MyDefaultService with #ConditionalOnMissingBean(MyService.class). Didn't work because MyDefaultService is never used, even if there is no other implementation of MyService.
There is an annotation called #Primarythat solves the problem. However, it needs to reside on MyCustomService, a class that I try to keep free of additional annotations. Essentially, I need the inverse annotation of #Primary on MyDefaultService. However, I couldn't find such an annotation.
Concrete use case
I am developing a service layer in one project, and a different project will implement a web UI layer on top of it. The UI project has a dependency to the service layer project. However, for certain functionalities implemented at the service layer, I need to know which user is currently logged in at the web context. So I have to define a service interface for that in the service layer project, such that it can be implemented by the UI project. However, for testing purposes in the service-layer project, I need a default implementation of that interface. Also, in case that the UI project team forgets to implement this interface, the app should not crash, but instead instantiate the fallback bean and issue a warning.
Thanks & kind regards,
Alan
I suggest writing an implementation of FactoryBean to do this. Your FactoryBean would scan the bean factory looking for beans that implement MyService, and if it finds one it returns that bean from getObject. If it doesn't, then it can instantiate MyDefaultService directly and return that. Your factory bean then gets annotated with #Primary.
So pieces like this (pseudo-code):
public class MyServiceFactory implements FactoryBean<MyService> {
ListableBeanFactory beanFactory;
public MyService getObject() {
Map beans = beanFactory.getBeansOfType(MyService.class)
if (beans.isEmpty())
return new MyDefaultService(); // plus args, obviously
else
return get_some_bean_from_the_map
}
}
and then
#Primary
#Bean
public MyServiceFactory MyServiceFactory() {
return new MyServiceFactory();
}
Spring will automatically handle the factory bean (i.e. it will make the MyService object available as a bean for injection like normal.
This solution doesn't require any special magic, and it's fairly obvious how it works. You can also handle errant cases such as multiple MyService beans being declared.
I'm working on a very small application connecting to a MySQL database.
I'm trying to create table record but getting 'no transaction in progress'.
I have all the right stuff in place:
a service interface MyService and its implementation MyServiceImpl
I have annotated the service impl with #Service
In the controller I used the interface name for the field #Autowired MyService
I have the correct transaction configuration as it was originally generated by roo
There is a public method MyService.create(...) which MyServiceImpl implements
But,
When I remote debug and inspect the controller's myService field what I see is something like
com.some.package.services.MyService#12345 (and NOT something like $Proxy73) which to me is not right, because what should be autowired is the proxy not he target bean (which is what I think this is). If I'm correct then it makes sense that there is no transaction as the annotation would only kick in when invoking a public method annotated with #Transactional on a proxy.
Please tell me why is spring injecting the target bean in this setup.
Thanks
If you have AspectJ-enabled transaction management (<tx:annotation-driven mode="aspectj" .../>) application of transactions happens in-place in the same class, either during build (compile-time weaving) or on startup (load-time weaving).
No new classes are created (like when using cglib) and no proxies (like with ordinary interface-based AOP in Spring). Instead bytecode of MyServiceImpl was modified directly without you even noticing. Unfortunately the only way to see AOP is to decompile your classes. If you use javap -c MyServiceImpl you'll find plenty of references to Spring transaction layer.
If you are using Spring MVC, make sure to scan specific controller classes alone in servlet context file. Otherwise it will scan 2 times and transaction is not available on the application context.
As far as I know, Spring uses JDK to generate dynamic proxy for the classes that implement any inferface while use Cglib to generate dynamic proxy for the classes that do not implement any inferface. For decarative transcation, Spring uses proxy to add transaction aspect. Please take a look at the code below:
interface Demo {
void methodA();
}
public class DemoImpl implements Demo{
#Transactional
public void updateA() {}
#Transactional
public void updateB() {}
}
I think updateA can work well with transaction. But how about updateB method? Does the #Transactional work for it?
Maybe my understanding is not correct. It's great if the related Spring source code is provided to explain how Spring use JDK/cglib to proxy the class and interface. Thanks
I have the config in the xml:
<tx:annotation-driven transaction-manager="transactionManager" />
JDK dynamic proxy
In this case your bean is wrapped with a proxy implementing Demo interface. From that moment you can only use that interface. Trying to inject or fetch bean of DemoImpl type will result in dreadful Abstract DAO pattern and Spring's "Proxy cannot be cast to ..." problem!
This kind of answers your question - you can only access updateA() and this is the only transactional method. Annotation around updateB() is ignored.
However if you call updateB() from updateA() it will be transactional because it will bind to a transaction started by updateA() (with default transaction propagation).
CGLIB proxy
In this case the interface is ignored. cglib will create a subclass of DemoImpl (obviously also implementing Demo interface) and apply transaction behaviour on both update*() methods. Now if you inject bean of type DemoImpl (interface is not needed in this case at all and Impl suffix is ugly) you can safely and transactionally call both methods.
See my article: Spring pitfalls: proxying and Spring AOP riddle for greater details.