public interface SmartClassLoader
If a ClassLoader does not implement this interface, then all the classes obtained from it should be considered as not reloadable (i.e. cacheable).
|Modifier and Type||Method and Description|
Return the original ClassLoader for this SmartClassLoader, or potentially the present loader itself if it is self-sufficient.
Determine whether the given class is reloadable (in this ClassLoader).
Define a custom class (typically a CGLIB proxy class) in this class loader.
default boolean isClassReloadable(Class<?> clazz)
Typically used to check whether the result may be cached (for this
ClassLoader) or whether it should be reobtained every time.
The default implementation always returns
clazz- the class to check (usually loaded from this ClassLoader)
Classobject) later on
default ClassLoader getOriginalClassLoader()
The default implementation returns the local ClassLoader reference as-is.
In case of a reloadable or other selectively overriding ClassLoader which
commonly deals with unaffected classes from a base application class loader,
this should get implemented to return the original ClassLoader that the
present loader got derived from (e.g. through
This gets specifically used in Spring's AOP framework to determine the class loader for a specific proxy in case the target class has not been defined in the present class loader. In case of a reloadable class loader, we prefer the base application class loader for proxying general classes not defined in the reloadable class loader itself.
default Class<?> publicDefineClass(String name, byte b, @Nullable ProtectionDomain protectionDomain)
This is a public equivalent of the protected
defineClass(String, byte, int, int, ProtectionDomain) method
ClassLoader which is traditionally invoked via reflection.
A concrete implementation in a custom class loader should simply delegate
to that protected method in order to make classloader-specific definitions
publicly available without "illegal access" warnings on JDK 9+:
return defineClass(name, b, 0, b.length, protectionDomain).
Note that the JDK 9+
Lookup#defineClass method does not support
a custom target class loader for the new definition; it rather always
defines the class in the same class loader as the lookup's context class.
name- the name of the class
b- the bytes defining the class
protectionDomain- the protection domain for the class, if any
LinkageError- in case of a bad class definition
SecurityException- in case of an invalid definition attempt
UnsupportedOperationException- in case of a custom definition attempt not being possible (thrown by the default implementation in this interface)
ClassLoader.defineClass(String, byte, int, int, ProtectionDomain)