spring-framework / org.springframework.beans / CachedIntrospectionResults

CachedIntrospectionResults

open class CachedIntrospectionResults

Internal class that caches JavaBeans java.beans.PropertyDescriptor information for a Java class. Not intended for direct use by application code.

Necessary for own caching of descriptors within the application's ClassLoader, rather than rely on the JDK's system-wide BeanInfo cache (in order to avoid leaks on ClassLoader shutdown).

Information is cached statically, so we don't need to create new objects of this class for every JavaBean we manipulate. Hence, this class implements the factory design pattern, using a private constructor and a static #forClass(Class) factory method to obtain instances.

Note that for caching to work effectively, some preconditions need to be met: Prefer an arrangement where the Spring jars live in the same ClassLoader as the application classes, which allows for clean caching along with the application's lifecycle in any case. For a web application, consider declaring a local org.springframework.web.util.IntrospectorCleanupListener in web.xml in case of a multi-ClassLoader layout, which will allow for effective caching as well.

In case of a non-clean ClassLoader arrangement without a cleanup listener having been set up, this class will fall back to a weak-reference-based caching model that recreates much-requested entries every time the garbage collector removed them. In such a scenario, consider the #IGNORE_BEANINFO_PROPERTY_NAME system property.

Author
Rod Johnson

Author
Juergen Hoeller

Since
05 May 2001

Properties

IGNORE_BEANINFO_PROPERTY_NAME

static val IGNORE_BEANINFO_PROPERTY_NAME: String

System property that instructs Spring to use the Introspector#IGNORE_ALL_BEANINFO mode when calling the JavaBeans Introspector: "spring.beaninfo.ignore", with a value of "true" skipping the search for BeanInfo classes (typically for scenarios where no such classes are being defined for beans in the application in the first place).

The default is "false", considering all BeanInfo metadata classes, like for standard Introspector#getBeanInfo(Class) calls. Consider switching this flag to "true" if you experience repeated ClassLoader access for non-existing BeanInfo classes, in case such access is expensive on startup or on lazy loading.

Note that such an effect may also indicate a scenario where caching doesn't work effectively: Prefer an arrangement where the Spring jars live in the same ClassLoader as the application classes, which allows for clean caching along with the application's lifecycle in any case. For a web application, consider declaring a local org.springframework.web.util.IntrospectorCleanupListener in web.xml in case of a multi-ClassLoader layout, which will allow for effective caching as well.

Functions

acceptClassLoader

open static fun acceptClassLoader(classLoader: ClassLoader): Unit

Accept the given ClassLoader as cache-safe, even if its classes would not qualify as cache-safe in this CachedIntrospectionResults class.

This configuration method is only relevant in scenarios where the Spring classes reside in a 'common' ClassLoader (e.g. the system ClassLoader) whose lifecycle is not coupled to the application. In such a scenario, CachedIntrospectionResults would by default not cache any of the application's classes, since they would create a leak in the common ClassLoader.

Any acceptClassLoader call at application startup should be paired with a #clearClassLoader call at application shutdown.

clearClassLoader

open static fun clearClassLoader(classLoader: ClassLoader): Unit

Clear the introspection cache for the given ClassLoader, removing the introspection results for all classes underneath that ClassLoader, and removing the ClassLoader (and its children) from the acceptance list.