org.daisy.common.stax.StaxEventHelper Maven / Gradle / Ivy
package org.daisy.common.stax;
import java.util.function.Predicate;
import java.util.Set;
import javax.xml.namespace.QName;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
/**
* The Class StaxEventHelper offers some stax utilities.
*/
public final class StaxEventHelper {
/**
* EventPredicates related helper functions.
*/
public static class EventPredicates {
/**
* Checks if is element
*
* @param name the name
* @return the predicate
*/
public static Predicate isElement(final QName name) {
return new Predicate() {
@Override
public boolean test(XMLEvent event) {
return event.isStartElement()
&& event.asStartElement().getName().equals(name);
}
};
}
/**
* Checks if is start or stop element.
*
* @param name the name
* @return the predicate
*/
public static Predicate isStartOrStopElement(final QName name) {
return new Predicate() {
@Override
public boolean test(XMLEvent event) {
return (event.isStartElement() && event.asStartElement()
.getName().equals(name))
|| (event.isEndElement() && event.asEndElement()
.getName().equals(name));
}
};
}
/** The I s_ star t_ element. */
public static Predicate IS_START_ELEMENT = new Predicate() {
@Override
public boolean test(XMLEvent event) {
return event.isStartElement();
}
};
/** The I s_ en d_ element. */
public static Predicate IS_END_ELEMENT = new Predicate() {
@Override
public boolean test(XMLEvent event) {
return event.isEndElement();
}
};
/**
* Checks if the event is child or siblings ChildOrSiblingPredicate.
*/
public static class ChildOrSiblingPredicate implements
Predicate {
/** The opened. */
private int opened = 1;
@Override
public boolean test(XMLEvent event) {
switch (event.getEventType()) {
case XMLEvent.START_ELEMENT:
opened++;
break;
case XMLEvent.END_ELEMENT:
opened--;
break;
default:
break;
}
return opened > 0;
}
};
/**
* Gets the child or sibling predicate.
*
* @return the child or sibling predicate
*/
public static Predicate getChildOrSiblingPredicate() {
return new ChildOrSiblingPredicate();
}
/**
* Checks if the event is offspring.
*/
public static class ChildPredicate implements Predicate {
/** The opened. */
private int opened = 0;
@Override
public boolean test(XMLEvent event) {
switch (event.getEventType()) {
case XMLEvent.START_ELEMENT:
opened++;
break;
case XMLEvent.END_ELEMENT:
opened--;
break;
default:
break;
}
return opened > 0;
}
}
/**
* Checks if is child predicate.
*
* @return the predicate
*/
public static Predicate isChildPredicate() {
return new ChildPredicate();
}
}
/**
* Peek next element matching the QName
*
* @param reader the reader
* @param name the name
* @return the start element
* @throws XMLStreamException the xML stream exception
*/
public static StartElement peekNextElement(XMLEventReader reader, QName name)
throws XMLStreamException {
while (reader.hasNext()) {
XMLEvent event = reader.peek();
if (event.isStartElement()
&& event.asStartElement().getName().equals(name)) {
return event.asStartElement();
}
reader.next();
}
throw new IllegalStateException("Element " + name + " not found");
}
/**
* Peek next element which mathces any QNames from the set provided
*
* @param reader the reader
* @param names the names
* @return the start element
* @throws XMLStreamException the xML stream exception
*/
public static StartElement peekNextElement(XMLEventReader reader,
Set names) throws XMLStreamException {
while (reader.hasNext()) {
XMLEvent event = reader.peek();
if (event.isStartElement()
&& names.contains(event.asStartElement().getName())) {
return event.asStartElement();
}
reader.next();
}
throw new IllegalStateException("Element not found");
}
/**
* Loops through the elements until the checker returns null or the element stream stops
*
* @param reader the reader
* @param filter the filter says whether the element has to be processed or not.
* @param checker the checker
* @param processor the processor
* @throws XMLStreamException the xML stream exception
*/
public static synchronized void loop(XMLEventReader reader,
Predicate filter, Predicate checker,
EventProcessor processor) throws XMLStreamException {
while (reader.hasNext()) {
XMLEvent event = reader.peek();
if (filter.test(event)) {
if (!checker.test(event)) {
break;
}
processor.process(event);
}
if (reader.hasNext()) {
reader.next();
}
}
}
/**
* Instantiates a new stax event helper.
*/
private StaxEventHelper() {
// no instantiation
}
}