I have Service.class with start() and asychronous() method :
public ResponseEntity<Object> start() throws APICommandConstructionException, APICommunicationException, APIReplyParseException,
APIErrorResponse, IOException {
List<Company> companiesList = dbHandler.retrieveCompaniesList();
Company company = null;
for (int i = 0; i < companiesList.size(); i++) {
asychronousMethod(companiesList, i, company);
}
return new ResponseEntity<Object>("Start method has Finished", HttpStatus.OK);
}
@Async("threadPoolTaskExecutor")
public void asychronousMethod(List<Company> companiesList, int i, Company company) throws APICommandConstructionException, APIReplyParseException, APICommunicationException, APIErrorResponse, IOException {
company = companiesList.get(i);
company = utils.websiteScrap(company);
companiesRepository.save(company);
}
Everything that is inside a loop doesn't run in parallel, but it starts second loop after first finished. Why is that? How to do it parallel?
In brief: you shouldn't call explicitly methods with Spring annotations.
More detailed:
Spring creates special proxies that on back-stage do 'magic' for you. So if you have async annotation, that means that (depending on compile- and runtime-configuration of Spring) there was some hidden part of code that is not executed when you invoke this.asynchronousMethod.
How to fix:
First of all method should match public CompletableFuture<Void> - such way you know when thread is complete.
Second instead of this you need resolve self-instance as Spring proxy.
The simplest way over @Autowired:
@Autowired
MyClass zhis;
.... //in for loop:
future = zhis.asychronousMethod(companiesList, i, company);
P.s please see good example at https://spring.io/guides/gs/async-method/