XML data types and operators

Derby supports the XML data type and a set of operators that work with the XML data type, but does not provide JDBC support for the XML data type. The XML data type and operators are based on a small subset of the SQL/XML specification.

The XML data type and operators are defined only in the SQL layer.

There is no JDBC-side support for XML data types. It is not possible to bind directly into an XML value or to retrieve an XML value directly from a result set. Instead, you must bind and retrieve the XML data as Java strings or character streams by explicitly specifying the appropriate XML operator as part of the SQL statements:

Additionally, there is no JDBC metadata support for the XML data type.

The XML data type is not allowed in any of the clauses or operations that are described in the section on expressions on LONG data types in Derby and standards.

For the XML operators to work properly, Derby requires that a JAXP parser, such as Apache Xerces, and an implementation of the DOM Level 3 XPath specification, such as Apache Xalan, are included in the Java classpath. If either the parser or the XPath processor is missing from the classpath, Derby disallows any XML-related operations.

Classpath and version issues

Most Java Virtual Machines (JVMs) that are version 1.6 or later, have the required libraries embedded in the JVM. If you are using one of these JVMs, you may not need to add any classes to your classpath.

If your JVM does not include the required libraries, you must add Apache Xalan, or some other library that implements the required functionality, to your classpath.

Some JVMs include a version of Xalan that is not new enough. If your JVM comes with a too old version of Xalan, you may need to override the version of Xalan in the JVM with a newer version by using the Endorsed Standards Override Mechanism described at http://download.oracle.com/javase/1.4.2/docs/guide/standards/. To use this mechanism, download and install a binary distribution of Xalan from Apache and set the system property java.endorsed.dirs to point to the Xalan installation directory.