Improve documentation for JavaConfig's use of CGLIB for all @Configuration annotated classes [SPR-6885]

[spring-projects-issues]

Michael Isvy opened SPR-6885 and commented

All @Configuration classes are dynamically subclassed with CGLIB, and the MethodInterceptor that is applied in the overridden versions of all @Bean methods check the container first for any cached (scoped) beans, of course including singletons.

See ConfigurationClassEnhancer and BeanMethodInterceptor for details.

For this reason, @Configuration classes have certain restrictions, such as that they (and their @Bean methods) may not be final; they must have a no-arg constructor, etc.

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Referenced from: commits 9e5b129, 6af9177

[spring-projects-issues]

Chris Beams commented

The changes to the documentation look good, Michael - thanks! You might consider adding one additional note that CGLIB is not a required dependency of Spring, so upon first use, users may get an error stating that CGLIB is required for processing @Configuration classes. This is of course resolved by adding CGLIB to the classpath via Maven, Ivy, etc.

[spring-projects-issues]

Chris Beams commented

also, the convention for section id naming in the @Configuration section is that the ids all start with 'beans-java-*'. Could you rename this to 'beans-java-implementation-notes', or something to that effect?