lux.xml.Serializer Maven / Gradle / Ivy
package lux.xml;
import java.util.HashMap;
import java.util.LinkedList;
import javax.xml.XMLConstants;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import lux.exception.LuxException;
import org.codehaus.stax2.DTDInfo;
import org.codehaus.stax2.XMLStreamReader2;
/**
* Accumulates a serialized XML document from StAX events according to a prescribed set of conventions,
* as follows:
* Line endings are normalized; CDATA blocks are preserved; entities and numeric references are preserved; redundant namespace
* declarations are dropped. Comments and processing instructions are preserved.
* No XML declaration is emitted. DOCTYPE declarations are preserved, but not the DTD internal subset.
* Empty elements are represented with both open and close tags.
*/
public class Serializer implements StAXHandler {
private StringBuilder doc;
private HashMap nsContextFrame;
private HashMap inScopeNamespaces;
private LinkedList> namespaceContexts;
public String getDocument () {
return doc.toString();
}
/**
* Consume the XML stream, saving text to the document buffer.
*
* @param r source of xml StAX events
* @param evtType the type of StAX event
*/
@Override
public void handleEvent (XMLStreamReader r, int evtType)
{
switch (evtType) {
case XMLStreamConstants.START_DOCUMENT:
inScopeNamespaces = new HashMap();
inScopeNamespaces.put("", "");
inScopeNamespaces.put("xml", XMLConstants.W3C_XML_SCHEMA_NS_URI);
namespaceContexts = new LinkedList>();
doc = new StringBuilder ();
break;
case XMLStreamConstants.CDATA:
doc.append("");
break;
case XMLStreamConstants.SPACE:
// fall through
case XMLStreamConstants.CHARACTERS:
appendText(r);
break;
case XMLStreamConstants.COMMENT:
doc.append("");
break;
case XMLStreamConstants.END_DOCUMENT:
doc.append('\n');
break;
case XMLStreamConstants.END_ELEMENT:
doc.append("");
unwindNamespaceContext();
break;
case XMLStreamConstants.ENTITY_DECLARATION:
case XMLStreamConstants.NOTATION_DECLARATION:
break;
case XMLStreamConstants.ENTITY_REFERENCE:
doc.append('&').append(r.getLocalName()).append(';');
break;
case XMLStreamConstants.PROCESSING_INSTRUCTION:
doc.append("");
break;
case XMLStreamConstants.START_ELEMENT:
{
nsContextFrame = null;
doc.append('<');
appendQName(r);
handleNamespace(r.getPrefix(), r.getNamespaceURI());
// Any declared namespaces?
for (int i = 0, len = r.getNamespaceCount(); i < len; ++i) {
handleNamespace (r.getNamespacePrefix(i), r.getNamespaceURI(i));
}
// And then the attributes:
for (int i = 0, len = r.getAttributeCount(); i < len; ++i) {
String prefix = r.getAttributePrefix(i);
doc.append (' ');
if (prefix != null && prefix.length() > 0) {
doc.append (prefix).append(':');
}
String value = r.getAttributeValue(i).replace("&", "&").replace("\"", """).replace("<", "<");
doc.append(r.getAttributeLocalName(i)).append ("=\"").append(value).append('"');
}
doc.append(">");
namespaceContexts.push(nsContextFrame);
}
break;
case XMLStreamConstants.DTD:
DTDInfo dtd;
try {
dtd = ((XMLStreamReader2)r).getDTDInfo();
} catch (XMLStreamException e) {
break;
}
doc.append("\n");
// Lose the DTD internal subset, sorry
break;
default:
throw new LuxException("Unexpected StAX event: " + r.getEventType());
}
}
private void appendText(XMLStreamReader r) {
int end = r.getTextStart() + r.getTextLength();
char [] c = r.getTextCharacters();
for (int i = r.getTextStart(); i < end; i++) {
// TODO: look ahead and copy characters in blocks?
switch (c[i]) {
case '<': doc.append("<"); break;
case '&': doc.append("&"); break;
default: doc.append(c[i]);
}
}
}
private void unwindNamespaceContext () {
HashMap nsContext = namespaceContexts.pop();
if (nsContext != null) {
inScopeNamespaces.putAll(nsContext);
}
}
private String handleNamespace(String prefix, String namespace) {
if (namespace == null) {
namespace = "";
}
if (prefix == null) {
prefix = "";
}
if (! namespace.equals(inScopeNamespaces.get(prefix))) {
appendNamespaceDeclaration (prefix, namespace);
if (nsContextFrame == null) {
nsContextFrame = new HashMap();
}
// retain the outer context so we can restore it later
nsContextFrame.put(prefix, inScopeNamespaces.get(prefix));
inScopeNamespaces.put (prefix, namespace);
}
return namespace;
}
private void appendNamespaceDeclaration(String prefix, String namespace) {
doc.append (" xmlns");
if (prefix.length() > 0) {
doc.append (':').append(prefix);
}
doc.append("=\"");
namespace = namespace.replace("\"", """);
doc.append(namespace);
doc.append("\"");
}
@Override
public void reset () {
doc = null;
namespaceContexts = null;
inScopeNamespaces = null;
namespaceContexts = null;
}
private void appendQName(XMLStreamReader r) {
String elemPrefix = r.getPrefix();
String ln = r.getLocalName();
if (elemPrefix != null && elemPrefix.length() > 0) {
doc.append (elemPrefix).append(':');
}
doc.append(ln);
}
}
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */