Object mapping with Java annotations

Abstract

Java applications often need to store data in external data sources. Large amounts of time can be spent developing solutions to integrate specific data sources into the application. The process of mapping object-oriented data to data sources can lead to a fragile system that can not handle incremental changes to the data or the integration of new data sources cleanly. Java 1.5 introduced a metadata facility called annotations into the Java language. Annotations can be used to describe data in a general way such that it can be mapped onto various types of data sources easily. The annotations are inspected at runtime by each data source persister, and a mapping is created. Implementations of two persisters are given: one for relational databases, and one for XML. Other new persisters can easily be added to the system.