Motivation

CDI apps usually consist of user business logic, libraries (e.g. DeltaSpike) and integration stuff (e.g. WildFly subsystems - JSF, Bean Validation, Batch). Most applications only use a small part of the beans provided by libraries and integrations. However, Weld has to retain the metadata for all beans in memory.

Measurements showed that a simple bean/producer method takes approx. 1-2 KB. Batch subsystem which is automatically enabled in WildFly registers ~ 60 beans (producers). One could exclude the subsystem completely but this approach has drawbacks. E.g. if you only use one the beans you cannot exclude the whole subsystem/bean archive.

Solution

Allow to instruct Weld to find "unused" beans and drop their metadata after bootstrap. An unused bean:

• is not a built-in bean, extension, interceptor, decorator
• does not have a name
• does not declare an observer
• is not eligible for injection to any injection point
• does not declare a producer which is eligible for injection to any injection point
• is not eligible for injection into any Instance<> injection point
• is not a cached result in any TypeSafeBeanResolver (this would mean that it was a result of programmatic lookup during bootstrap, unless an anonymous inner class AnnotationLiteral was used) this one probably does not make much sense
• is not an application entry point

Problems:

1. Programmatic lookup - no easy way to detect, at least Instance<> injection points should be considered (the only problem is probably CDI.current().select())
2. EE components might be installed after Weld initialization finished - this cleanup must be performed after all EE components are installed this is a requirement if ALLOW_OPTIMIZED_CLEANUP==true
3. How to identify application entry points (such as JAX-RS resource) - this will probably require some SPI

Configuration

User should be able to exclude some beans from removal. E.g. a regular expression might be used to match the bean classes which are included/excluded.

Integrators

We should probably add a new method to org.jboss.weld.bootstrap.api.Bootstrap with the following contract:

• optional - an integrator is not required to invoke this method
• must be invoked after Bootstrap.endInitialization() and after all EE components which support injection are installed (i.e. relevant ProcessInjectionTarget was fired)
• attempts to optimize stored metadata to save memory

See also ConfigurationKey#ALLOW_OPTIMIZED_CLEANUP.