CODEWITHSUNDEEP
byte-buddy
Eyal Koren
Eyal Koren

Reputation: 13

Byte Buddy LocationStrategy types

I saw that the default LocationStrategy is STRONG, which keeps a strong reference to the class loader when creating a ClassFileLocator. Does this mean Byte Buddy can prevent a class loader from being garbage collected (eg when undeploying a webapp from a servlet container) or is there another mechanism to evacuate those?

Also in this regard- the documentation about the WEAK strategy says a ClassFileLocator will "stop working" after the corresponding class loader is garbage collected. What are the implications? How would a locator for a garbage-collected class loader be used?

Upvotes: 1

Views: 115

Answers (1)

Rafael Winterhalter
Rafael Winterhalter

Reputation: 44032

You are right about your assertion. With a strong type locator, all TypeDescriptions will reference the class loader as dependent types are resolved lazily. This means for example that if you look up a type's field type, that type will only be loaded if you are using it for the first time what might never happen.

Typically, those type descriptions are not stored over the life time of a class being loaded. Since the class loader will never be garbage collected during a loading of one of its classes, referencing the class loader strongly does not render any issue. However, once you want to cache type descriptions in between multiple class loadings (what can make a lot of sence since some applications load thousands of classes using the same class loader), this might become a problem if a class loader would be garbage collected while the cache is still referencing the type description with the underlying class loader.

In this case, reusing the type descriptions will be problematic since no lazily referenced classes can be resolved after the class loader was garbage collected. Note that a type description might be resolved using a specific class loader while the class is defined by a parent of that class loader which is why this might be a problem.

Typically, if you maintain a cache of type descriptions per class loader, this should however not be a problem.

Upvotes: 1

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