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/*
* $Id: BaseXMLEventWriter.java,v 1.9 2005/03/09 22:34:34 cniles Exp $
*
* Copyright (c) 2004, Christian Niles, Unit12
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of Christian Niles, Unit12, nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
package javanet.staxutils;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.xml.namespace.NamespaceContext;
import javax.xml.namespace.QName;
import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.*;
/**
* Base class for {@link XMLEventWriter} implementations. This implemenation
* buffers Attribute and Namespace events as specified in the specification,
* maintains a stack of NamespaceContext instances based on the events it
* receives, and repairs any missing namespaces. Subclasses should implement the
* {@link #sendEvent(XMLEvent)} method to receive the processed events and
* perform additional processing.
*
* @author Christian Niles
* @version $Revision: 1.9 $
*/
public abstract class BaseXMLEventWriter implements XMLEventWriter {
/**
* XMLEventFactory used to construct XMLEvent instances.
*/
protected XMLEventFactory factory;
/** list of {@link SimpleNamespaceContext}s. */
protected List nsStack = new ArrayList();
/**
* Reference to the last StartElement sent. This will be null if no
* StartElement has been sent, or after a non Attribute/Namespace
* event is received.
*/
protected StartElement lastStart;
/**
* LinkedHashMap of attribute events sent surrounding the last
* StartElement. By using LinkedHashMap, the attributes will stay in the
* order they were defined.
*/
protected Map attrBuff = new LinkedHashMap();
/**
* LinkedHashMap of namespace events sent surrounding the last
* StartElement. By using LinkedHashMap, the namespaces will stay in the
* order they were defined.
*/
protected Map nsBuff = new LinkedHashMap();
/**
* Whether this writer has been closed or not.
*/
protected boolean closed;
protected BaseXMLEventWriter() {
this(null, null);
}
protected BaseXMLEventWriter(XMLEventFactory eventFactory,
NamespaceContext nsCtx) {
if (nsCtx != null) {
nsStack.add(new SimpleNamespaceContext(nsCtx));
} else {
nsStack.add(new SimpleNamespaceContext());
}
if (eventFactory != null) {
factory = eventFactory;
} else {
factory = XMLEventFactory.newInstance();
}
}
public synchronized void flush() throws XMLStreamException {
if (!closed) {
sendCachedEvents();
}
}
/**
* Sends any events that have been cached in anticipation of further events.
*
* @throws XMLStreamException If an error occurs sending the events.
*/
private void sendCachedEvents() throws XMLStreamException {
if (lastStart != null) {
// A StartElement, and possibly attributes and namespaces, have been
// cached. We need to combine them all into a single StartElement
// event to send to sendEvent(XMLEvent)
// First, construct the new NamespaceContext for the tag
SimpleNamespaceContext nsCtx = this.pushNamespaceStack();
// List used to store any defaulted/rewritten namespaces
List namespaces = new ArrayList();
// merge namespaces
mergeNamespaces(lastStart.getNamespaces(), namespaces);
mergeNamespaces(nsBuff.values().iterator(), namespaces);
nsBuff.clear();
// merge attributes
List attributes = new ArrayList();
mergeAttributes(lastStart.getAttributes(), namespaces, attributes);
mergeAttributes(attrBuff.values().iterator(), namespaces,
attributes);
attrBuff.clear();
// determine the name of the new start tag
QName tagName = lastStart.getName();
QName newName = processQName(tagName, namespaces);
// construct new element
StartElement newStart = factory.createStartElement(
newName.getPrefix(), newName.getNamespaceURI(),
newName.getLocalPart(), attributes.iterator(),
namespaces.iterator(), nsCtx);
lastStart = null;
sendEvent(newStart);
} else {
// no start element was cached, but we may have cached some
// namespaces and attributes that need to be written.
for (Iterator i = nsBuff.values().iterator(); i.hasNext();) {
XMLEvent evt = (XMLEvent) i.next();
sendEvent(evt);
}
nsBuff.clear();
for (Iterator i = attrBuff.values().iterator(); i.hasNext();) {
XMLEvent evt = (XMLEvent) i.next();
sendEvent(evt);
}
attrBuff.clear();
}
}
/**
* Merges a set of {@link Attribute} events, possibly adding additional
* {@link Namespace} events if the attribute's prefix isn't bound in the
* provided context.
*
* @param iter An {@link Iterator} of {@link Attribute} events.
* @param namespaces A {@link List} to which any new {@link Namespace}
* events should be added.
* @param attributes A {@link List} to which all {@link Attributes} events
* should be merged.
*/
private void mergeAttributes(Iterator iter, List namespaces, List attributes) {
while (iter.hasNext()) {
Attribute attr = (Attribute) iter.next();
// check if the attribute QName has the proper mapping
QName attrName = attr.getName();
QName newName = processQName(attrName, namespaces);
if (!attrName.equals(newName)) {
// need to generate a new attribute with the new qualified name
Attribute newAttr = factory.createAttribute(newName,
attr.getValue());
attributes.add(newAttr);
} else {
// the attribute is fine
attributes.add(attr);
}
}
}
/**
* Merges a set of {@link Namespaces} events into the provided {@link List}.
*
* @param iter An {@link Iterator} of {@link Namespace}s to merge.
* @param namespaces A {@link List} containing all added {@link Namespace}
* events.
* @throws XMLStreamException If a conflicting namespace binding is
* encountered.
*/
private void mergeNamespaces(Iterator iter, List namespaces)
throws XMLStreamException {
// for each namespace, add it to the context, and place it in the list
while (iter.hasNext()) {
Namespace ns = (Namespace) iter.next();
String prefix = ns.getPrefix();
String nsURI = ns.getNamespaceURI();
SimpleNamespaceContext nsCtx = this.peekNamespaceStack();
if (!nsCtx.isPrefixDeclared(prefix)) {
// mapping doesn't exist, so add it to the context/list
if (prefix == null || prefix.length() == 0) {
nsCtx.setDefaultNamespace(nsURI);
} else {
nsCtx.setPrefix(prefix, nsURI);
}
namespaces.add(ns);
} else if (!nsCtx.getNamespaceURI(prefix).equals(nsURI)) {
throw new XMLStreamException("Prefix already declared: " + ns,
ns.getLocation());
} else {
// duplicate namespace declaration
}
}
}
/**
* Processes a {@link QName}, possibly rewriting it to match the current
* namespace context.
*
* @param name The {@link QName} to process.
* @param namespaces A {@link List} of {@link Namespace} events to which any
* new namespace bindings should be added.
* @return The new name, or the name parameter if no changes
* were necessary.
*/
private QName processQName(QName name, List namespaces) {
// get current context
SimpleNamespaceContext nsCtx = this.peekNamespaceStack();
// get name parts
String nsURI = name.getNamespaceURI();
String prefix = name.getPrefix();
if (prefix != null && prefix.length() > 0) {
// prefix provided; see if it is okay in current context, otherwise we'll
// have to rewrite it
String resolvedNS = nsCtx.getNamespaceURI(prefix);
if (resolvedNS != null) {
if (!resolvedNS.equals(nsURI)) {
// prefix is already bound to a different namespace; we have to
// find or generate and alternative prefix
String newPrefix = nsCtx.getPrefix(nsURI);
if (newPrefix == null) {
// no existing prefix; need to generate a new prefix
newPrefix = generatePrefix(nsURI, nsCtx, namespaces);
}
// return the newly prefixed name
return new QName(nsURI, name.getLocalPart(), newPrefix);
} else {
// prefix bound to proper namespace; name is already ok
}
} else if (nsURI != null && nsURI.length() > 0) {
// prefix isn't bound yet; bind it and the name is good to go
nsCtx.setPrefix(prefix, nsURI);
namespaces.add(factory.createNamespace(prefix, nsURI));
}
return name;
} else if (nsURI != null && nsURI.length() > 0) {
// name is namespaced, but has no prefix associated with it. Look for an
// existing prefix, or generate one.
String newPrefix = nsCtx.getPrefix(nsURI);
if (newPrefix == null) {
// no existing prefix; need to generate a new prefix
newPrefix = generatePrefix(nsURI, nsCtx, namespaces);
}
// return the newly prefixed name
return new QName(nsURI, name.getLocalPart(), newPrefix);
} else {
// name belongs to no namespace and has no prefix.
return name;
}
}
/**
* Generates a new namespace prefix for the specified namespace URI that
* doesn't collide with any existing prefix.
*
* @param nsURI The URI for which to generate a prefix.
* @param nsCtx The namespace context in which to set the prefix.
* @param namespaces A {@link List} of {@link Namespace} events to which the
* new prefix will be added.
* @return The new prefix.
*/
private String generatePrefix(String nsURI, SimpleNamespaceContext nsCtx,
List namespaces) {
String newPrefix;
int nsCount = 0;
do {
newPrefix = "ns" + nsCount;
nsCount++;
} while (nsCtx.getNamespaceURI(newPrefix) != null);
nsCtx.setPrefix(newPrefix, nsURI);
namespaces.add(factory.createNamespace(newPrefix, nsURI));
return newPrefix;
}
public synchronized void close() throws XMLStreamException {
if (closed) {
return;
}
try {
flush();
} finally {
closed = true;
}
}
public synchronized void add(XMLEvent event) throws XMLStreamException {
if (closed) {
throw new XMLStreamException("Writer has been closed");
}
// If the event is an Attribute or Namespace, cache it; otherwise, we
// should send any previously cached items
switch (event.getEventType()) {
case XMLEvent.NAMESPACE :
cacheNamespace((Namespace) event);
return;
case XMLEvent.ATTRIBUTE :
cacheAttribute((Attribute) event);
return;
default :
// send any cached events
sendCachedEvents();
}
if (event.isStartElement()) {
// cache the start element in case any following Attribute or
// Namespace events occur
lastStart = event.asStartElement();
return;
} else if (event.isEndElement()) {
if (nsStack.isEmpty()) {
throw new XMLStreamException("Mismatched end element event: "
+ event);
}
SimpleNamespaceContext nsCtx = this.peekNamespaceStack();
EndElement endTag = event.asEndElement();
QName endElemName = endTag.getName();
String prefix = endElemName.getPrefix();
String nsURI = endElemName.getNamespaceURI();
if (nsURI != null && nsURI.length() > 0) {
// check that the prefix used in the name is bound to the same
// namespace
String boundURI = nsCtx.getNamespaceURI(prefix);
if (!nsURI.equals(boundURI)) {
// not equal! now we must see what prefix it's actually
// bound to
String newPrefix = nsCtx.getPrefix(nsURI);
if (newPrefix != null) {
QName newName = new QName(nsURI,
endElemName.getLocalPart(), newPrefix);
event = factory.createEndElement(newName,
endTag.getNamespaces());
} else {
// no prefix is bound! report an error
throw new XMLStreamException("EndElement namespace ("
+ nsURI + ") isn't bound [" + endTag + "]");
}
}
} else {
// default namespace
String defaultURI = nsCtx.getNamespaceURI("");
if (defaultURI != null && defaultURI.length() > 0) {
throw new XMLStreamException("Unable to write " + event
+ " because default namespace is occluded by "
+ defaultURI);
}
// else, namespace matches and can be written directly
}
// pop the stack
popNamespaceStack();
}
sendEvent(event);
}
public void add(XMLEventReader reader) throws XMLStreamException {
while (reader.hasNext()) {
add(reader.nextEvent());
}
}
public synchronized String getPrefix(String nsURI)
throws XMLStreamException {
return getNamespaceContext().getPrefix(nsURI);
}
public synchronized void setPrefix(String prefix, String nsURI)
throws XMLStreamException {
peekNamespaceStack().setPrefix(prefix, nsURI);
}
public synchronized void setDefaultNamespace(String nsURI)
throws XMLStreamException {
peekNamespaceStack().setDefaultNamespace(nsURI);
}
public synchronized void setNamespaceContext(NamespaceContext root)
throws XMLStreamException {
SimpleNamespaceContext parent = (SimpleNamespaceContext) nsStack.get(0);
parent.setParent(root);
}
public synchronized NamespaceContext getNamespaceContext() {
return peekNamespaceStack();
}
/**
* Removes the active {@link SimpleNamespaceContext} from the top of the
* stack.
*
* @return The {@link SimpleNamespaceContext} removed from the namespace
* stack.
*/
protected SimpleNamespaceContext popNamespaceStack() {
return (SimpleNamespaceContext) nsStack.remove(nsStack.size() - 1);
}
/**
* Returns the active {@link SimpleNamespaceContext} from the top of the
* stack.
*
* @return The active {@link SimpleNamespaceContext} from the top of the
* stack.
*/
protected SimpleNamespaceContext peekNamespaceStack() {
return (SimpleNamespaceContext) nsStack.get(nsStack.size() - 1);
}
/**
* Creates a new {@link SimpleNamespaceContext} and adds it to the top of
* the stack.
*
* @return The new {@link SimpleNamespaceContext}.
*/
protected SimpleNamespaceContext pushNamespaceStack() {
SimpleNamespaceContext nsCtx;
SimpleNamespaceContext parent = peekNamespaceStack();
if (parent != null) {
nsCtx = new SimpleNamespaceContext(parent);
} else {
nsCtx = new SimpleNamespaceContext();
}
nsStack.add(nsCtx);
return nsCtx;
}
/**
* Adds the specified {@link Attribute} to the attribute cache.
*
* @param attr The attribute to cache.
*/
protected void cacheAttribute(Attribute attr) {
attrBuff.put(attr.getName(), attr);
}
/**
* Adds the provided {@link Namespace} event to the namespace cache. The
* current namespace context will not be affected.
*
* @param ns The namespace to add to the cache.
*/
protected void cacheNamespace(Namespace ns) {
nsBuff.put(ns.getPrefix(), ns);
}
/**
* Called by the methods of this class to write the event to the stream.
*
* @param event The event to write.
* @throws XMLStreamException If an error occurs processing the event.
*/
protected abstract void sendEvent(XMLEvent event) throws XMLStreamException;
}
