[SYNCOPE-1635] Use singleton bean for each domain for each rule with conf - #264
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| String domainableBeanNameWithConf = domain + clazz.getName(); | ||
| DefaultListableBeanFactory beanFactory = ApplicationContextProvider.getBeanFactory(); | ||
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| if (beanFactory.containsSingleton(domainableBeanNameWithConf)) { |
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The same exact if with statement is also performed in the synchronized block: why?
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This is a double-check lock pattern. Thread takes monitor and executes the logic regarding initialization. Another thread waits until the the monitor is realeased. As soon as first thread releases monitor -> second thread proceeds its work and reaches the additional if clause. As the bean already exists (created by first thread) the second thread is not creating a bean again and not registers it as a singleton one more time.
Do you see any disadvantages it this?
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I see, there is wide literature abut double-check lock pattern, and some is not very pleasant with it, especially for Java implementations.
What would be the disadvantage of simply removing the first if and leaving the whole logic in the synchronized block?
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IMHO: Adding of the additional if clause gives a small improvement in performance (because the acquiring of monitor is not requested).
Am I wrong?
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I am not completely convinced, but let that be :-)
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