JAVA REFLECTION BOOKS CODE

JAVA REFLECTION BOOKS CODE

Each lesson contains code examples, tips, and troubleshooting information. This trail covers common uses of reflection for accessing and manipulating classes, fields, methods, and constructors. Reflective code breaks abstractions and therefore may change behavior with upgrades of the platform. Exposure of Internals Since reflection allows code to perform operations that would be illegal in non-reflective code, such as accessing private fields and methods, the use of reflection can result in unexpected side-effects, which may render code dysfunctional and may destroy portability. This is in an important consideration for code which has to run in a restricted security context, such as in an Applet. Security Restrictions Reflection requires a runtime permission which may not be present when running under a security manager. Consequently, reflective operations have slower performance than their non-reflective counterparts, and should be avoided in sections of code which are called frequently in performance-sensitive applications. Performance Overhead Because reflection involves types that are dynamically resolved, certain Java virtual machine optimizations can not be performed. The following concerns should be kept in mind when accessing code via reflection. If it is possible to perform an operation without using reflection, then it is preferable to avoid using it.

Reflection is powerful, but should not be used indiscriminately.

Test harnesses can make use of reflection to systematically call a discoverable set APIs defined on a class, to insure a high level of code coverage in a test suite. Debuggers and Test Tools Debuggers need to be able to examine private members on classes. Visual development environments can benefit from making use of type information available in reflection to aid the developer in writing correct code. Class Browsers and Visual Development Environments A class browser needs to be able to enumerate the members of classes. Extensibility Features An application may make use of external, user-defined classes by creating instances of extensibility objects using their fully-qualified names. With that caveat in mind, reflection is a powerful technique and can enable applications to perform operations which would otherwise be impossible. This is a relatively advanced feature and should be used only by developers who have a strong grasp of the fundamentals of the language. Reflection is commonly used by programs which require the ability to examine or modify the runtime behavior of applications running in the Java virtual machine.

Java reflection books