org.daisy.common.transform.XMLOutputValue Maven / Gradle / Ivy

Go to download
package org.daisy.common.transform;

import java.util.function.Consumer;

import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLStreamWriter;

import org.daisy.common.stax.BaseURIAwareXMLStreamWriter;

import org.w3c.dom.Node;

/**
 * A consumer of a XDM value that is a sequence of nodes, or an "external" item that can be
 * unmarshaled from a sequence of nodes.
 *
 * This interface has several sub-interfaces. Instances may implement one or more of them:
 * 
 *   {@link XMLEventWriter}
 *   {@link XMLStreamWriter}
 *   {@link Consumer}{@code <}{@link Node}{@code >}
 * 
 */
public class XMLOutputValue extends OutputValue {

	private XMLOutputValue backingValue = null;
	private BaseURIAwareXMLStreamWriter streamWriter = null;
	private Consumer nodeConsumer = null;

	public XMLOutputValue(BaseURIAwareXMLStreamWriter value) {
		streamWriter = value;
	}

	public XMLOutputValue(Consumer value) {
		nodeConsumer = value;
	}

	protected XMLOutputValue() {
	}

	protected XMLOutputValue(XMLOutputValue value) {
		backingValue = value;
	}

	/**
	 * A sequence of XML events, as a {@link XMLStreamWriter}.
	 */
	public BaseURIAwareXMLStreamWriter asXMLStreamWriter() throws UnsupportedOperationException {
		if (backingValue != null)
			return backingValue.asXMLStreamWriter();
		else if (streamWriter != null)
			return streamWriter;
		else
			throw new UnsupportedOperationException();
	}

	/**
	 * The purpose of this method is to be overridden by subclasses, e.g. to implement a lazy output.
	 */
	public void writeXMLStream(Consumer stream) throws UnsupportedOperationException {
		stream.accept(asXMLStreamWriter());
	}

	/**
	 * A sequence of XML events, as a {@link XMLEventWriter}.
	 */
	public XMLEventWriter asXMLEventWriter() throws UnsupportedOperationException {
		if (backingValue != null)
			return backingValue.asXMLEventWriter();
		else
			throw new UnsupportedOperationException();
	}

	/**
	 * A sequence of nodes, as a {@link Consumer}{@code <}{@link Node}{@code >}.
	 */
	public Consumer asNodeConsumer() throws UnsupportedOperationException {
		if (backingValue != null)
			return backingValue.asNodeConsumer();
		else if (nodeConsumer != null)
			return nodeConsumer;
		else
			throw new UnsupportedOperationException();
	}
}