Attribute-oriented programming

Attribute-oriented programming (@OP) is a technique for embedding metadata, namely attributes, within program code.

Java
With the inclusion of Metadata Facility for Java (JSR-175) into the J2SE 5.0 release it is possible to utilize attribute-oriented programming right out of the box. XDoclet library makes it possible to use attribute-oriented programming approach in earlier versions of Java.

C#
The C# language has supported attributes from its very first release. These attributes was used to give run-time information and are not used by a preprocessor. Currently with source generators, you can use attributes to drive generation of additional code at compile-time.

UML
The Unified Modeling Language (UML) supports a kind of attribute called stereotypes.

Hack
The Hack programming language supports attributes. Attributes can be attached to various program entities, and information about those attributes can be retrieved at run-time via reflection.

Tools

 * Annotation Processing Tool (apt)
 * Spoon, an Annotation-Driven Java Program Transformer
 * XDoclet, a Javadoc-Driven Program Generator