/*
* Copyright 2004-2006 the original author or authors.
*
* Licensed 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.compass.core.util.config;
import java.util.ArrayList;
import java.util.BitSet;
import org.xml.sax.Attributes;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;
/**
* A SAXConfigurationHandler helps build Configurations out of sax events.
*/
public class SAXConfigurationHandler extends DefaultHandler implements ErrorHandler {
/**
* Likely number of nested configuration items. If more is encountered the
* lists will grow automatically.
*/
private static final int EXPECTED_DEPTH = 5;
private final ArrayList m_elements = new ArrayList(EXPECTED_DEPTH);
private final ArrayList m_values = new ArrayList(EXPECTED_DEPTH);
/**
* Contains true at index n if space in the configuration with depth n is to
* be preserved.
*/
private final BitSet m_preserveSpace = new BitSet();
private ConfigurationHelper m_configuration;
private Locator m_locator;
/**
* Get the configuration object that was built.
*/
public ConfigurationHelper getConfiguration() {
return m_configuration;
}
/**
* Clears all data from this configuration handler.
*/
public void clear() {
m_elements.clear();
m_values.clear();
m_locator = null;
}
/**
* Set the document <code>Locator</code> to use.
*/
public void setDocumentLocator(final Locator locator) {
m_locator = locator;
}
/**
* Handling hook for character data.
*/
public void characters(final char[] ch, int start, int end) throws SAXException {
// it is possible to play micro-optimization here by doing
// manual trimming and thus preserve some precious bits
// of memory, but it's really not important enough to justify
// resulting code complexity
final int depth = m_values.size() - 1;
final StringBuffer valueBuffer = (StringBuffer) m_values.get(depth);
valueBuffer.append(ch, start, end);
}
/**
* Handling hook for finishing parsing of an element.
*/
public void endElement(final String namespaceURI, final String localName, final String rawName) throws SAXException {
final int depth = m_elements.size() - 1;
final XmlConfigurationHelper finishedConfiguration = (XmlConfigurationHelper) m_elements.remove(depth);
final String accumulatedValue = ((StringBuffer) m_values.remove(depth)).toString();
if (finishedConfiguration.getChildren().length == 0) {
// leaf node
String finishedValue;
if (m_preserveSpace.get(depth)) {
finishedValue = accumulatedValue;
} else if (0 == accumulatedValue.length()) {
finishedValue = null;
} else {
finishedValue = accumulatedValue.trim();
}
finishedConfiguration.setValue(finishedValue);
} else {
final String trimmedValue = accumulatedValue.trim();
if (trimmedValue.length() > 0) {
throw new SAXException("Not allowed to define mixed content in the " + "element "
+ finishedConfiguration.getName() + " at " + finishedConfiguration.getLocation());
}
}
if (0 == depth) {
m_configuration = finishedConfiguration;
}
}
/**
* Create a new <code>DefaultConfiguration</code> with the specified local
* name and location.
*/
protected XmlConfigurationHelper createConfiguration(final String localName, final String location) {
return new XmlConfigurationHelper(localName, location);
}
/**
* Handling hook for starting parsing of an element.
*/
public void startElement(final String namespaceURI, final String localName, final String rawName,
final Attributes attributes) throws SAXException {
final XmlConfigurationHelper configuration = createConfiguration(rawName, getLocationString());
// depth of new configuration (not decrementing here, configuration
// is to be added)
final int depth = m_elements.size();
boolean preserveSpace = false; // top level element trims space by
// default
if (depth > 0) {
final XmlConfigurationHelper parent = (XmlConfigurationHelper) m_elements.get(depth - 1);
parent.addChild(configuration);
// inherits parent's space preservation policy
preserveSpace = m_preserveSpace.get(depth - 1);
}
m_elements.add(configuration);
m_values.add(new StringBuffer());
final int attributesSize = attributes.getLength();
for (int i = 0; i < attributesSize; i++) {
final String name = attributes.getQName(i);
final String value = attributes.getValue(i);
if (!name.equals("xml:space")) {
configuration.setAttribute(name, value);
} else {
preserveSpace = value.equals("preserve");
}
}
if (preserveSpace) {
m_preserveSpace.set(depth);
} else {
m_preserveSpace.clear(depth);
}
}
/**
* This just throws an exception on a parse error.
*/
public void error(final SAXParseException exception) throws SAXException {
throw exception;
}
/**
* This just throws an exception on a parse error.
*/
public void warning(final SAXParseException exception) throws SAXException {
throw exception;
}
/**
* This just throws an exception on a parse error.
*/
public void fatalError(final SAXParseException exception) throws SAXException {
throw exception;
}
/**
* Returns a string showing the current system ID, line number and column
* number.
*/
protected String getLocationString() {
if (null == m_locator) {
return "Unknown";
} else {
final int columnNumber = m_locator.getColumnNumber();
return m_locator.getSystemId() + ":" + m_locator.getLineNumber()
+ (columnNumber >= 0 ? (":" + columnNumber) : "");
}
}
}
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