Java Architecture for XML Binding (JAXB) allows Java developers to map Java classes to XML representations. JAXB provides two main features: the ability to marshal Java objects into XML and the inverse, i.e. to unmarshal XML back into Java objects. In other words, JAXB allows storing and retrieving data in memory in any XML format, without the need to implement a specific set of XML loading and saving routines for the program's class structure.

JAXB is particularly useful when the specification is complex and changing. In such a case, regularly changing the XML Schema definitions to keep them synchronised with the Java definitions can be time consuming and error prone.

JAXB is one of the APIs in the Java EE platform, and is part of the Java Web Services Development Pack (JWSDP). It is also one of the foundations for WSIT. JAXB is part of SE version 1.6.

JAXB 1.0 was developed under the Java Community Process as JSR 31. As of 2006, JAXB 2.0 is being developed under JSR 222. Reference implementations for these specifications are available under the CDDL open source license at java.net.

Usage

The tool "xjc" can be used to convert XML Schema and other schema file types (as of Java 1.6, RELAX NG and XML DTDs are supported experimentally) to class representations. Classes are marked up using annotations from javax.xml.bind.annotation.* namespace, for example, @XmlRootElement and @XmlElement. XML list sequences are represented by attributes of type java.util.List. Marshallers and Unmarshallers are created through an instance of JAXBContext.

In addition, JAXB includes a "schemagen" tool that can essentially perform the inverse of "xjc", creating an XML Schema from a set of annotated classes.

Default data type bindings

The Java language provides a richer set of data types than XML schema. The table below lists the mappings of XML data types to Java data types in JAXB.