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Code to walk an XML Schema and confirm an XML Document conforms to it.
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.ws.commons.schema.docpath;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.apache.ws.commons.schema.XmlSchemaCollection;
import org.apache.ws.commons.schema.XmlSchemaElement;
import org.apache.ws.commons.schema.constants.Constants;
import org.apache.ws.commons.schema.walker.XmlSchemaAttrInfo;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
/**
* Builds an XML {@link org.w3c.dom.Document} from an XML Schema during a SAX
* walk.
*/
public final class DomBuilderFromSax extends DefaultHandler {
private static final String XSI_NS = "http://www.w3.org/2001/XMLSchema-instance";
private static final String XSI_SCHEMALOC = "schemaLocation";
private static final String XSI_NIL = "nil";
private Document document;
private StringBuilder content;
private Map namespaceToLocationMapping;
private List newPrefixes;
private XmlSchemaNamespaceContext nsContext;
private Map elementsByQName;
private final ArrayList elementStack;
private final DocumentBuilder docBuilder;
private final XmlSchemaCollection schemas;
private final Set globalNamespaces;
/**
* Creates a new DocumentBuilderFromSax.
*
* @throws ParserConfigurationException If unable to create a
* {@link DocumentBuilder}.
*/
public DomBuilderFromSax(XmlSchemaCollection xmlSchemaCollection) throws ParserConfigurationException {
if (xmlSchemaCollection == null) {
throw new IllegalArgumentException("xmlSchemaCollection cannot be null.");
}
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
docBuilder = factory.newDocumentBuilder();
elementStack = new ArrayList();
newPrefixes = new ArrayList();
nsContext = new XmlSchemaNamespaceContext();
document = null;
content = null;
namespaceToLocationMapping = null;
elementsByQName = null;
schemas = xmlSchemaCollection;
globalNamespaces = new HashSet();
globalNamespaces.add("http://www.w3.org/2001/XMLSchema-instance");
}
/**
* @see org.xml.sax.helpers.DefaultHandler#startDocument()
*/
@Override
public void startDocument() throws SAXException {
document = docBuilder.newDocument();
document.setXmlStandalone(true);
}
/**
* @see org.xml.sax.helpers.DefaultHandler#startPrefixMapping(String,
* String)
*/
@Override
public void startPrefixMapping(String prefix, String uri) throws SAXException {
nsContext.addNamespace(prefix, uri);
newPrefixes.add(prefix);
}
/**
* @see org.xml.sax.helpers.DefaultHandler#endPrefixMapping(String)
*/
@Override
public void endPrefixMapping(String prefix) throws SAXException {
nsContext.removeNamespace(prefix);
}
/**
* Starts a new element in the generated XML document. If the previous
* element was not closed, adds this element as a child to that element.
*
* @see DefaultHandler#startElement(String, String, String, Attributes)
*/
@Override
public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
addContentToCurrentElement(false);
final Element element = document.createElementNS((uri.length() == 0) ? null : uri, qName);
// Define New Prefixes
for (String newPrefix : newPrefixes) {
final String namespace = nsContext.getNamespaceURI(newPrefix);
if (namespace == null) {
throw new SAXException("Prefix " + newPrefix + " is not recognized.");
}
String qualifiedName = null;
if (newPrefix.length() > 0) {
qualifiedName = Constants.XMLNS_ATTRIBUTE + ':' + newPrefix;
} else {
qualifiedName = Constants.XMLNS_ATTRIBUTE;
}
try {
element.setAttributeNS(Constants.XMLNS_ATTRIBUTE_NS_URI, qualifiedName, namespace);
} catch (DOMException e) {
throw new IllegalStateException("Cannot add namespace attribute ns=\""
+ Constants.XMLNS_ATTRIBUTE_NS_URI + "\", qn=\""
+ qualifiedName + "\", value=\"" + namespace
+ "\" to element \"" + qName + "\".", e);
}
}
newPrefixes.clear();
// Add Attributes
final QName elemQName = new QName(uri, localName);
XmlSchemaStateMachineNode stateMachine = null;
if (elementsByQName != null) {
stateMachine = elementsByQName.get(elemQName);
}
for (int attrIndex = 0; attrIndex < atts.getLength(); ++attrIndex) {
String attrUri = atts.getURI(attrIndex);
if (attrUri.length() == 0) {
attrUri = null;
}
boolean isGlobal = globalNamespaces.contains(attrUri);
if ((attrUri != null) && !isGlobal) {
final QName attrQName = new QName(attrUri, atts.getLocalName(attrIndex));
boolean found = false;
if (stateMachine != null) {
for (XmlSchemaAttrInfo attrInfo : stateMachine.getAttributes()) {
if (attrInfo.getAttribute().getQName().equals(attrQName)) {
found = true;
isGlobal = attrInfo.isTopLevel();
}
}
}
if (!found && (schemas.getAttributeByQName(attrQName) != null)) {
isGlobal = true;
}
}
final String attrValue = atts.getValue(attrIndex);
if (!isGlobal) {
element.setAttribute(atts.getLocalName(attrIndex), attrValue);
} else {
element.setAttributeNS(attrUri, atts.getQName(attrIndex), attrValue);
}
}
// Update the Parent Element
if (!elementStack.isEmpty()) {
elementStack.get(elementStack.size() - 1).appendChild(element);
} else {
addNamespaceLocationMappings(element);
document.appendChild(element);
}
elementStack.add(element);
}
/**
* Adds content to the current element.
*
* @see DefaultHandler#characters(char[], int, int)
*/
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
if (content == null) {
content = new StringBuilder();
}
content.append(ch, start, length);
}
/**
* Closes the current element in the generated XML document.
*
* @see DefaultHandler#endElement(String, String, String)
*/
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
addContentToCurrentElement(true);
if (elementStack.isEmpty()) {
StringBuilder errMsg = new StringBuilder("Attempted to end element {");
errMsg.append(uri).append('}').append(localName);
errMsg.append(", but the stack is empty!");
throw new IllegalStateException(errMsg.toString());
}
final Element element = elementStack.remove(elementStack.size() - 1);
final String ns = (uri.length() == 0) ? null : uri;
final boolean namespacesMatch = (((ns == null) && (element.getNamespaceURI() == null)) || ((ns != null) && ns
.equals(element.getNamespaceURI())));
if (!namespacesMatch || !element.getLocalName().equals(localName)) {
StringBuilder errMsg = new StringBuilder("Attempted to end element {");
errMsg.append(ns).append('}').append(localName).append(", but found {");
errMsg.append(element.getNamespaceURI()).append('}');
errMsg.append(element.getLocalName()).append(" on the stack instead!");
throw new IllegalStateException(errMsg.toString());
}
}
/**
* @see org.xml.sax.helpers.DefaultHandler#endDocument()
*/
@Override
public void endDocument() throws SAXException {
if (!elementStack.isEmpty()) {
StringBuilder errMsg = new StringBuilder("Ending an XML document with ");
errMsg.append(elementStack.size()).append(" elements still open.");
elementStack.clear();
throw new IllegalStateException(errMsg.toString());
}
}
private void addContentToCurrentElement(boolean isEnd) {
if ((content == null) || (content.length() == 0)) {
/*
* If we reached the end of the element, check if we received any
* content. If not, and if the element is nillable, write a nil
* attribute.
*/
if (isEnd && !elementStack.isEmpty() && (schemas != null)) {
final Element currElem = elementStack.get(elementStack.size() - 1);
if (currElem.getChildNodes().getLength() == 0) {
final QName elemQName = new QName(currElem.getNamespaceURI(), currElem.getLocalName());
XmlSchemaElement schemaElem = null;
if (elementsByQName != null) {
final XmlSchemaStateMachineNode stateMachine = elementsByQName.get(elemQName);
if ((stateMachine != null)
&& stateMachine.getNodeType().equals(XmlSchemaStateMachineNode.Type.ELEMENT)) {
schemaElem = stateMachine.getElement();
}
}
if (schemaElem == null) {
schemaElem = schemas.getElementByQName(elemQName);
}
if ((schemaElem != null) && schemaElem.isNillable()) {
currElem.setAttributeNS(XSI_NS, XSI_NIL, "true");
}
}
}
return;
}
if (elementStack.isEmpty()) {
StringBuilder errMsg = new StringBuilder("Attempted to add content \"");
errMsg.append(content.toString()).append("\", but there were no ");
errMsg.append("elements in the stack!");
throw new IllegalStateException(errMsg.toString());
}
elementStack.get(elementStack.size() - 1).appendChild(document.createTextNode(content.toString()));
content.delete(0, content.length());
}
/**
* Retrieves the document constructed from the SAX walk.
*/
public Document getDocument() {
return document;
}
/**
* Retrieves the XML Schema namespace -> location mapping set by the last
* call to {@link #setNamespaceToLocationMapping(Map)}.
*/
public Map getNamespaceToLocationMapping() {
return namespaceToLocationMapping;
}
/**
* Sets the XML Schema namespace -> location mapping to use when defining
* the schemaLocation attribute in the generated XML document.
*
* @param nsToLocMapping The namespace -> location mapping.
*/
public void setNamespaceToLocationMapping(Map nsToLocMapping) {
namespaceToLocationMapping = nsToLocMapping;
}
/**
* Retrieves the {@link QName} -> {@link XmlSchemaStateMachineNode} mapping
* defined by the call to {@link #setStateMachinesByQName(Map)}.
*/
public Map getStateMachinesByQName() {
return elementsByQName;
}
/**
* Sets the mapping of {@link QName}s to {@link XmlSchemaStateMachineNode}s.
* This is used to disambiguate:
*
* - Whether empty content indicates nil
* - If an element's attribute requires a namespace
*
*
* @param statesByQName The state-machine-node-by-QName mapping.
*/
public void setStateMachinesByQName(Map statesByQName) {
elementsByQName = statesByQName;
}
private void addNamespaceLocationMappings(Element rootElement) {
if ((namespaceToLocationMapping == null) || namespaceToLocationMapping.isEmpty()
|| rootElement.hasAttributeNS(XSI_NS, XSI_SCHEMALOC)) {
/*
* There are no namesapces mappings to add, or a namespace mapping
* already exists.
*/
return;
}
StringBuilder schemaList = new StringBuilder();
for (Map.Entry e : namespaceToLocationMapping.entrySet()) {
schemaList.append(e.getKey()).append(' ').append(e.getValue());
schemaList.append(' ');
}
schemaList.delete(schemaList.length() - 1, schemaList.length());
rootElement.setAttributeNS(XSI_NS, XSI_SCHEMALOC, schemaList.toString());
}
}
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