[GitHub] [syncope] DmitriyBrashevets commented on a change in pull request #264: [SYNCOPE-1635] Use singleton bean for each domain for each rule with conf

[GitBox <gi...@apache.org>]

DmitriyBrashevets commented on a change in pull request #264:
URL: https://github.com/apache/syncope/pull/264#discussion_r636167234



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File path: core/spring/src/main/java/org/apache/syncope/core/spring/ImplementationManager.java
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@@ -216,28 +217,27 @@
     }
 
     @SuppressWarnings("unchecked")
-    private static <T> T buildJavaWithConf(final Class<T> clazz) {
-        T bean = null;
-
+    private static <T> T buildJavaWithConf(final String domain, final Class<T> clazz) {
         if (clazz != null) {
-            if (ApplicationContextProvider.getBeanFactory().containsSingleton(clazz.getName())) {
-                bean = (T) ApplicationContextProvider.getBeanFactory().getSingleton(clazz.getName());
-            } else {
-                try {
-                    bean = (T) ApplicationContextProvider.getBeanFactory().
-                            createBean(clazz, AbstractBeanDefinition.AUTOWIRE_BY_TYPE, false);
-                    ApplicationContextProvider.getBeanFactory().registerSingleton(clazz.getName(), bean);
-                } catch (IllegalStateException e) {
-                    LOG.debug("While attempting to register {}", clazz.getName(), e);
+            String domainableBeanNameWithConf = domain + clazz.getName();
+            DefaultListableBeanFactory beanFactory = ApplicationContextProvider.getBeanFactory();
+
+            if (beanFactory.containsSingleton(domainableBeanNameWithConf)) {

Review comment:
       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 threads 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.
   
   
   Do you see any disadvantages it this?




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