ConfigurationXMLReader.java
/*
* 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.commons.configuration2;
import java.io.IOException;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.AttributesImpl;
/**
* <p>
* A base class for "faked" {@code XMLReader} classes that transform a configuration object in a set of SAX
* parsing events.
* </p>
* <p>
* This class provides dummy implementations for most of the methods defined in the {@code XMLReader} interface that are
* not used for this special purpose. There will be concrete sub classes that process specific configuration classes.
* </p>
*/
public abstract class ConfigurationXMLReader implements XMLReader {
/** Constant for the namespace URI. */
protected static final String NS_URI = "";
/** Constant for the default name of the root element. */
private static final String DEFAULT_ROOT_NAME = "config";
/** An empty attributes object. */
private static final Attributes EMPTY_ATTRS = new AttributesImpl();
/** Stores the content handler. */
private ContentHandler contentHandler;
/** Stores an exception that occurred during parsing. */
private SAXException exception;
/** Stores the name for the root element. */
private String rootName;
/**
* Creates a new instance of {@code ConfigurationXMLReader}.
*/
protected ConfigurationXMLReader() {
rootName = DEFAULT_ROOT_NAME;
}
/**
* Fires a SAX characters event.
*
* @param text the text
*/
protected void fireCharacters(final String text) {
if (getException() == null) {
try {
final char[] ch = text.toCharArray();
getContentHandler().characters(ch, 0, ch.length);
} catch (final SAXException ex) {
exception = ex;
}
}
}
/**
* Fires a SAX element end event.
*
* @param name the name of the affected element
*/
protected void fireElementEnd(final String name) {
if (getException() == null) {
try {
getContentHandler().endElement(NS_URI, name, name);
} catch (final SAXException ex) {
exception = ex;
}
}
}
/**
* Fires a SAX element start event.
*
* @param name the name of the actual element
* @param attribs the attributes of this element (can be <b>null</b>)
*/
protected void fireElementStart(final String name, final Attributes attribs) {
if (getException() == null) {
try {
final Attributes at = attribs == null ? EMPTY_ATTRS : attribs;
getContentHandler().startElement(NS_URI, name, name, at);
} catch (final SAXException ex) {
exception = ex;
}
}
}
/**
* Gets the actually set content handler.
*
* @return the content handler
*/
@Override
public ContentHandler getContentHandler() {
return contentHandler;
}
/**
* Gets the DTD handler. This class does not support DTD handlers, so this method always returns <b>null</b>.
*
* @return the DTD handler
*/
@Override
public DTDHandler getDTDHandler() {
return null;
}
/**
* Gets the entity resolver. This class does not support an entity resolver, so this method always returns
* <b>null</b>.
*
* @return the entity resolver
*/
@Override
public EntityResolver getEntityResolver() {
return null;
}
/**
* Gets the error handler. This class does not support an error handler, so this method always returns <b>null</b>.
*
* @return the error handler
*/
@Override
public ErrorHandler getErrorHandler() {
return null;
}
/**
* Gets a reference to an exception that occurred during parsing.
*
* @return a SAXExcpetion or <b>null</b> if none occurred
*/
public SAXException getException() {
return exception;
}
/**
* Dummy implementation of the interface method.
*
* @param name the name of the feature
* @return always <b>false</b> (no features are supported)
*/
@Override
public boolean getFeature(final String name) {
return false;
}
/**
* Gets a reference to the configuration that is parsed by this object.
*
* @return the parsed configuration
*/
public abstract Configuration getParsedConfiguration();
/**
* Dummy implementation of the interface method. No properties are supported, so this method always returns <b>null</b>.
*
* @param name the name of the requested property
* @return the property value
*/
@Override
public Object getProperty(final String name) {
return null;
}
/**
* Gets the name to be used for the root element.
*
* @return the name for the root element
*/
public String getRootName() {
return rootName;
}
/**
* Parses the actual configuration object. The passed input source will be ignored.
*
* @param input the input source (ignored)
* @throws IOException if no configuration was specified
* @throws SAXException if an error occurs during parsing
*/
@Override
public void parse(final InputSource input) throws IOException, SAXException {
parseConfiguration();
}
/**
* Parses the current configuration object. The passed system ID will be ignored.
*
* @param systemId the system ID (ignored)
* @throws IOException if no configuration was specified
* @throws SAXException if an error occurs during parsing
*/
@Override
public void parse(final String systemId) throws IOException, SAXException {
parseConfiguration();
}
/**
* Parses the configuration object and generates SAX events. This is the main processing method.
*
* @throws IOException if no configuration has been specified
* @throws SAXException if an error occurs during parsing
*/
protected void parseConfiguration() throws IOException, SAXException {
if (getParsedConfiguration() == null) {
throw new IOException("No configuration specified!");
}
if (getContentHandler() != null) {
exception = null;
getContentHandler().startDocument();
processKeys();
if (getException() != null) {
throw getException();
}
getContentHandler().endDocument();
}
}
/**
* Processes all keys stored in the actual configuration. This method is called by {@code parseConfiguration()} to start
* the main parsing process. {@code parseConfiguration()} calls the content handler's {@code startDocument()} and
* {@code endElement()} methods and cares for exception handling. The remaining actions are left to this method that
* must be implemented in a concrete sub class.
*
* @throws IOException if an IO error occurs
* @throws SAXException if a SAX error occurs
*/
protected abstract void processKeys() throws IOException, SAXException;
/**
* Sets the content handler. The object specified here will receive SAX events during parsing.
*
* @param handler the content handler
*/
@Override
public void setContentHandler(final ContentHandler handler) {
contentHandler = handler;
}
/**
* Sets the DTD handler. The passed value is ignored.
*
* @param handler the handler to be set
*/
@Override
public void setDTDHandler(final DTDHandler handler) {
}
/**
* Sets the entity resolver. The passed value is ignored.
*
* @param resolver the entity resolver
*/
@Override
public void setEntityResolver(final EntityResolver resolver) {
}
/**
* Sets the error handler. The passed value is ignored.
*
* @param handler the error handler
*/
@Override
public void setErrorHandler(final ErrorHandler handler) {
}
/**
* Dummy implementation of the interface method.
*
* @param name the name of the feature to be set
* @param value the value of the feature
*/
@Override
public void setFeature(final String name, final boolean value) {
}
/**
* Dummy implementation of the interface method. No properties are supported, so a call of this method just has no
* effect.
*
* @param name the property name
* @param value the property value
*/
@Override
public void setProperty(final String name, final Object value) {
}
/**
* Sets the name for the root element.
*
* @param string the name for the root element.
*/
public void setRootName(final String string) {
rootName = string;
}
}