I am new to Spring Transaction. Something that I found really odd, probably I did understand this properly.
I wanted to have a transactional around method level and I have a caller method within the same class and it seems like it does not like that, it has to be called from the separate class. I don't understand how is that possible.
If anyone has an idea how to resolve this issue, I would greatly appreciate. I would like to use the same class to call the annotated transactional method.
Here is the code:
public class UserService {
#Transactional
public boolean addUser(String userName, String password) {
try {
// call DAO layer and adds to database.
} catch (Throwable e) {
TransactionAspectSupport.currentTransactionStatus()
.setRollbackOnly();
}
}
public boolean addUsers(List<User> users) {
for (User user : users) {
addUser(user.getUserName, user.getPassword);
}
}
}
It's a limitation of Spring AOP (dynamic objects and cglib).
If you configure Spring to use AspectJ to handle the transactions, your code will work.
The simple and probably best alternative is to refactor your code. For example one class that handles users and one that process each user. Then default transaction handling with Spring AOP will work.
Configuration tips for handling transactions with AspectJ
To enable Spring to use AspectJ for transactions, you must set the mode to AspectJ:
<tx:annotation-driven mode="aspectj"/>
If you're using Spring with an older version than 3.0, you must also add this to your Spring configuration:
<bean class="org.springframework.transaction.aspectj
.AnnotationTransactionAspect" factory-method="aspectOf">
<property name="transactionManager" ref="transactionManager" />
</bean>
In Java 8+ there's another possibility, which I prefer for the reasons given below:
#Service
public class UserService {
#Autowired
private TransactionHandler transactionHandler;
public boolean addUsers(List<User> users) {
for (User user : users) {
transactionHandler.runInTransaction(() -> addUser(user.getUsername, user.getPassword));
}
}
private boolean addUser(String username, String password) {
// TODO call userRepository
}
}
#Service
public class TransactionHandler {
#Transactional(propagation = Propagation.REQUIRED)
public <T> T runInTransaction(Supplier<T> supplier) {
return supplier.get();
}
#Transactional(propagation = Propagation.REQUIRES_NEW)
public <T> T runInNewTransaction(Supplier<T> supplier) {
return supplier.get();
}
}
This approach has the following advantages:
It may be applied to private methods. So you don't have to break encapsulation by making a method public just to satisfy Spring limitations.
Same method may be called within different transaction propagations and it is up to the caller to choose the suitable one. Compare these 2 lines:
transactionHandler.runInTransaction(() -> userService.addUser(user.getUserName, user.getPassword));
transactionHandler.runInNewTransaction(() -> userService.addUser(user.getUserName, user.getPassword));
It is explicit, thus more readable.
The problem here is, that Spring's AOP proxies don't extend but rather wrap your service instance to intercept calls. This has the effect, that any call to "this" from within your service instance is directly invoked on that instance and cannot be intercepted by the wrapping proxy (the proxy is not even aware of any such call). One solutions is already mentioned. Another nifty one would be to simply have Spring inject an instance of the service into the service itself, and call your method on the injected instance, which will be the proxy that handles your transactions. But be aware, that this may have bad side effects too, if your service bean is not a singleton:
<bean id="userService" class="your.package.UserService">
<property name="self" ref="userService" />
...
</bean>
public class UserService {
private UserService self;
public void setSelf(UserService self) {
this.self = self;
}
#Transactional
public boolean addUser(String userName, String password) {
try {
// call DAO layer and adds to database.
} catch (Throwable e) {
TransactionAspectSupport.currentTransactionStatus()
.setRollbackOnly();
}
}
public boolean addUsers(List<User> users) {
for (User user : users) {
self.addUser(user.getUserName, user.getPassword);
}
}
}
With Spring 4 it's possible to Self autowired
#Service
#Transactional
public class UserServiceImpl implements UserService{
#Autowired
private UserRepository repository;
#Autowired
private UserService userService;
#Override
public void update(int id){
repository.findOne(id).setName("ddd");
}
#Override
public void save(Users user) {
repository.save(user);
userService.update(1);
}
}
This is my solution for self invocation:
public class SBMWSBL {
private SBMWSBL self;
#Autowired
private ApplicationContext applicationContext;
#PostConstruct
public void postContruct(){
self = applicationContext.getBean(SBMWSBL.class);
}
// ...
}
You can autowired BeanFactory inside the same class and do a
getBean(YourClazz.class)
It will automatically proxify your class and take into account your #Transactional or other aop annotation.
Here is what I do for small projects with only marginal usage of method calls within the same class. In-code documentation is strongly advised, as it may look strange to colleagues. But it works with singletons, is easy to test, simple, quick to achieve and spares me the full blown AspectJ instrumentation. However, for more heavy usage I'd advice the AspectJ solution as described in Espens answer.
#Service
#Scope(proxyMode = ScopedProxyMode.TARGET_CLASS)
class PersonDao {
private final PersonDao _personDao;
#Autowired
public PersonDao(PersonDao personDao) {
_personDao = personDao;
}
#Transactional
public void addUser(String username, String password) {
// call database layer
}
public void addUsers(List<User> users) {
for (User user : users) {
_personDao.addUser(user.getUserName, user.getPassword);
}
}
}
The issue is related to how spring load classes and proxies. It will not work , untill you write your inner method / transaction in another class or go to other class and then again come to your class and then write the inner nested transcation method.
To summarize, spring proxies does not allow the scenarios which you are facing. you have to write the 2nd transaction method in other class
There is no point to use AspectJ or Other ways. Just using AOP is sufficient. So, we can add #Transactional to addUsers(List<User> users) to solve current issue.
public class UserService {
private boolean addUser(String userName, String password) {
try {
// call DAO layer and adds to database.
} catch (Throwable e) {
TransactionAspectSupport.currentTransactionStatus()
.setRollbackOnly();
}
}
#Transactional
public boolean addUsers(List<User> users) {
for (User user : users) {
addUser(user.getUserName, user.getPassword);
}
}
}
I want to write common code which should be execute before every method,
Where can I place this code in spring.
Thanks in advance.
What you ask is not trivial but Aspect Oriented Programming (AoP) is one way to achieve that. This description assumes that you are somewhat familiar with the Proxy class, the InvocationHandler interface and the Interceptor pattern in general. As I said, not a totally trivial matter.
Define the logic that you what to be executed before every method, or some method or whatever. Usually it is some kind of Interceptor, this is an example:
public class TimeProfilerInterceptor implements MethodInterceptor {
#Getter
private final TimeStatistics statistics = new TimeStatistics();
#Override
public Object invoke(MethodInvocation invocation) throws Throwable {
StopWatch watch = new StopWatch();
try {
watch.start();
Object returnValue = invocation.proceed();
return returnValue;
}
finally {
// etc...
}
}
}
Define a place where your logic is wired to your methods. In this example, the place is a Spring component that extends AbstractBeanFactoryAwareAdvisingPostProcessor and implements InitializingBean. The afterPropertiesSet method is called by Spring once the initialization of the bean is done. The method uses the Advice class from spring-aop to identify the pointcuts i.e. the methods that must be wrapped by the interceptor. In this case, it is an annotation based pointcut, meaning that it matches every method that has a certain custom annotation on it (TimeProfiled).
#Component
public class TimeProfiledAnnotationPostProcessor
extends AbstractBeanFactoryAwareAdvisingPostProcessor
implements InitializingBean {
#Autowired
TimeProfilerInterceptor timeProfilerInterceptor;
#Override
public void afterPropertiesSet() throws Exception {
this.setProxyTargetClass(true);
Advice advice = timeProfilerInterceptor;
Pointcut pointcut = new AnnotationMatchingPointcut(null, TimeProfiled.class);
this.advisor = new DefaultPointcutAdvisor(pointcut, advice);
}
}
Define your custom annotation to use where needed.
#Target(ElementType.METHOD)
#Retention(RetentionPolicy.RUNTIME)
public #interface TimeProfiled {
}
Tell Spring to initiate the wrapping mechanism at startup via the following annotation upon a Spring Configuration or a SpringBootApplication:
#ComponentScan(basePackageClasses = TimeProfiledAnnotationPostProcessor.class)
#EnableAspectJAutoProxy(proxyTargetClass = true)
You can change the pointcut so that it matches other methods with other criteria, there is an entire syntax to do that, a world in itself, this is just a small example...
You should have a look at Spring AOP. With Spring AOP you can write Aspects which can be common code which is executed before/after a method. The following example is a simple Aspect:
#Aspect
public class EmployeeAspect {
#Before("execution(public String getName())")
public void getNameAdvice(){
System.out.println("Executing Advice on getName()");
}
#Before("execution(* your.package.name.*.get*())")
public void getAllAdvice(){
System.out.println("Service method getter called");
}
}
Within the #Before() annotation you can specify the exact method which is surrounded with the Aspect or you use the wildcard * to specify more methods. For this, you should be familiar with Pointcut expressions.
I try to understand why this code doesn't work
In component:
#PostConstruct
public void runAtStart(){
testStream();
}
#Transactional(readOnly = true)
public void testStream(){
try(Stream<Person> top10ByFirstName = personRepository.findTop10ByFirstName("Tom")){
top10ByFirstName.forEach(System.out::println);
}
}
And repository :
public interface PersonRepository extends JpaRepository<Person, Long> {
Stream<Person> findTop10ByFirstName(String firstName);
}
I get:
org.springframework.dao.InvalidDataAccessApiUsageException: You're trying to execute a streaming query method without a surrounding transaction that keeps the connection open so that the Stream can actually be consumed. Make sure the code consuming the stream uses #Transactional or any other way of declaring a (read-only) transaction.
One key thing about Spring is that many annotated features use proxies to provide the annotation functionality. That is #Transactional, #Cacheable and #Async all rely on Spring detecting those annotations and wrapping those beans in a proxy bean.
That being the case, a proxied method can only be used when invoked on the class and not from within the class. See this about the topic.
Try:
Refactoring and call this #Transactional method from another class in your context, or
By self-autowiring the class into itself and calling the #Transactional method that way.
To demonstrate (1):
public class MyOtherClass {
#Autowired
private MyTestStreamClass myTestStreamClass;
#PostConstruct
public void runAtStart(){
// This will invoke the proxied interceptors for `#Transactional`
myTestStreamClass.testStream();
}
}
To demonstrate (2):
#Component
public class MyTestStreamClass {
#Autowired
private MyTestStreamClass myTestStreamClass;
#PostConstruct
public void runAtStart(){
// This will invoke the proxied interceptors for `#Transactional` since it's self-autowired
myTestStreamClass.testStream();
}
#Transactional(readOnly = true)
public void testStream(){
try(Stream<Person> top10ByFirstName = personRepository.findTop10ByFirstName("Tom")){
top10ByFirstName.forEach(System.out::println);
}
}
}
I'm trying to output a log message whenever the function someFunction() gets invoked.
This is my Aspect:
#Aspect
#Component
public class MyAspect {
private static final Logger LOGGER = Logger.getLogger(MyAspect.class.getName());
#Pointcut("execution(com.practice.AOP.someFunction())")
public void outputLogMessage() {
LOGGER.info("someFunction has been invoked");
}
}
The method i'm trying to intercept, someFunction(), is in the com.practice.AOP class. When I invoke it (shown below), my Advice (the log message) doesn't output, nor do I get an error. What am I doing wrong? Is Pointcut even the way to go?
#SpringBootApplication
public class AOP {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
someFunction();
}
public static void someFunction() {
//should invoke the log message
}
}
Spring AOP only works on Spring beans, and only on public instance methods of those spring beans invoked from the outside (i.e. this.publicMethod() style invocations will not work, as they are not going through the proxies that Spring AOP creates to advise your spring beans.
If that is not enough for you, for instance if you need to advise not just spring beans but non-spring managed code as well, or static methods like in your example, you will need to switch to native AspectJ support, either by compile time weaving, or by load time weaving.
I am getting started with AOP for the first time.
I have my first aspect as follows:
#Aspect
public class SyncLoggingAspect {
private final Logger logger = Logger.getLogger(this.getClass());
#Before("execution(public * *(..))")
public void anyPublic() {
System.out.println("HIT POINTCUT");
}
}
This sucessfully proceeds to be invoked on any method call which is public. However when I change it to this:
#Before("execution(public * doPoll(..))")
public void anyPublic() {
System.out.println("HIT POINTCUT");
}
I would expect it to work on any public method called "doPoll", yet when a method such as this is called nothing happens:
public class GmailContactPoller extends ContactPoller<GoogleUser, ContactPusher<GoogleUser>> {
Logger logger = Logger.getLogger(this.getClass());
#Override
public List<? extends ContactPusher<GoogleUser>> doPoll() throws PollException {
...
}
}
Is there something I am missing with the EL syntax? Or is this something to do with the inheritance hierarchy? The superclass method of doPoll is abstract in an abstract class called Poller. Does not having an interface cause problems?
Edit: I just noticed my IDE enables spring aspect tooling, and now I have the following compiler warning by the method:
"Description Resource Path Location Type
advice defined in datasync.aop.aspects.SyncLoggingAspect has not been applied [Xlint:adviceDidNotMatch] SyncLoggingAspect.java /DataSync/src/main/datasync/aop/aspects"
Spring AOP Proxies and aspectJ had some differences mainly:
Spring AOP only works on public methods.
Spring AOP does not work for self invocations.
You can have a look to sections 8.4 & 8.5 of Spring's Documentation for more information.
Currently you have two solutions:
refactor your code to remove the need for self invocation
use AspectJ rather than Spring AOP proxies either at compile time or load time.
Try:
#Before("execution(public * *.doPoll(..))")
public void anyPublic() {
System.out.println("HIT POINTCUT");
}