JDBCSQLXML.java 文件源码

/**
 * Returns a Source for reading the XML value designated by this SQLXML
 * instance. <p>
 *
 * @param sourceClass The class of the source, or null.  If null, then a
 *      DOMSource is returned.
 * @return a Source for reading the XML value.
 * @throws SQLException if there is an error processing the XML value
 *   or if the given <tt>sourceClass</tt> is not supported.
 */
protected <T extends Source>T getSourceImpl(
        Class<T> sourceClass) throws SQLException {

    if (JAXBSource.class.isAssignableFrom(sourceClass)) {

        // Must go first presently, since JAXBSource extends SAXSource
        // (purely as an implementation detail) and it's not possible
        // to instantiate a valid JAXBSource with a Zero-Args
        // constructor(or any subclass thereof, due to the finality of
        // its private marshaller and context object attributes)
        // FALL THROUGH... will throw an exception
    } else if (StreamSource.class.isAssignableFrom(sourceClass)) {
        return createStreamSource(sourceClass);
    } else if ((sourceClass == null)
               || DOMSource.class.isAssignableFrom(sourceClass)) {
        return createDOMSource(sourceClass);
    } else if (SAXSource.class.isAssignableFrom(sourceClass)) {
        return createSAXSource(sourceClass);
    } else if (StAXSource.class.isAssignableFrom(sourceClass)) {
        return createStAXSource(sourceClass);
    }

    throw JDBCUtil.invalidArgument("sourceClass: " + sourceClass);
}