State and Singletons" https://www.youtube.com/watch?v=-FRm3VPhseI Stack Overflow: What is so bad about Singletons? “The worst part of this whole topic is that the people who hate singletons rarely https://stackoverflow.com/questions/137975/what-is-so-bad-about-singletons ## What's currently out there Google: The Clean Code Talks - "Global State and Singletons" https://www.youtube.com/watch?v=-FRm3VPhseI v=-FRm3VPhseI Stack Overflow: What is so bad about Singletons? “The worst part of this whole topic is that the people who hate singletons practical rarely give concrete suggestions for what to use instead.”

already double-quoted (SPR-12252) allow for further locking optimizations for the retrieval of non-singletons beans (SPR-12250) improved error messages for MockRestServiceServer (SPR-12230) allow spring ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now

already double-quoted (SPR-12252) allow for further locking optimizations for the retrieval of non-singletons beans (SPR-12250) improved error messages for MockRestServiceServer(SPR-12230) allow spring HTTP ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now

ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now prototype beans receive independent collection/array even when based on single * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained

ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now beans receive independent collection/array even when based on single value * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained

ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now beans receive independent collection/array even when based on single value * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained

ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now beans receive independent collection/array even when based on single value * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained

gDispatcherServletInitializer.getServletConfigClasses() fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods post-processors * inner beans detected as Application Listeners as well (only supported for inner singletons) * child bean definition's scope attribute can be inherited from parent bean definition now beans receive independent collection/array even when based on single value * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained

ervletInitializer.getServletConfigClasses() (SPR-12028) fixed ConcurrentMapCacheManager has interdependent setters (SPR-12026) fixed documentation typo (SPR-12020) fixed Spring may invoke @Bean methods beans receive independent collection/array even when based on single value * registered plain singletons will be fully matched according to their qualifiers * @Qualifier value matching takes chained supported by default as well * ApplicationListener beans get obtained on demand, supporting non-singletons as well * ApplicationListeners will be called in the order according to the Ordered contract

complexity, more and more languages get added. Tests get added for various components which are all interdependent. For example if you have a shared database then tests which mutate the same data cannot be run