Other Reflexive Components

Beyond the classes included in the API, there are a few other classes, some of which have even preceded the Reflection API, which provide some sort of reflection capabilities [metaXa and the Future of Reflection. Golm and Kleinoder].

• SecurityManager - In order to determine whether some code has the right to invoke a method, say of the Socket class, the security manager bases its decision on the current execution stack and the class loaders used to load the classes on the stack. In order to know these, some amount of reflection takes place. For example, the (protected) method getClassContext() returns the state of the current execution stack as an array of Classes.

• Class loaders - Class loaders can transform an array of bytes (something that might be modified or even created at runtime) into a class. This is a good example of reflection, however, going the reverse way (reification) is not possible, ie. transforming a class into data structure (array of bytes) that can be analyzed and manipulated. The Reflection API gives some ability to analyze the structure of a class but that is all.

• References - The classes in java.lang.ref (for example, WeakReference) provide some sort of reflective abilities, in terms of being able to analyze such information as memory utilization. Looks scary.