/*
* 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.configuration;
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</code> 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</code> interface that are not used for this
* special purpose. There will be concrete sub classes that process specific
* configuration classes.</p>
*
* @author <a href="mailto:[email protected]">Oliver Heger</a>
* @version $Id: ConfigurationXMLReader.java 439648 2006-09-02 20:42:10Z oheger $
*/
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</code>.
*/
protected ConfigurationXMLReader()
{
super();
setRootName(DEFAULT_ROOT_NAME);
}
/**
* Parses the acutal 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
*/
public void parse(String systemId) throws IOException, SAXException
{
parseConfiguration();
}
/**
* Parses the acutal 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
*/
public void parse(InputSource input) throws IOException, SAXException
{
parseConfiguration();
}
/**
* Dummy implementation of the interface method.
*
* @param name the name of the feature
* @return always <b>false</b> (no features are supported)
*/
public boolean getFeature(String name)
{
return false;
}
/**
* Dummy implementation of the interface method.
*
* @param name the name of the feature to be set
* @param value the value of the feature
*/
public void setFeature(String name, boolean value)
{
}
/**
* Returns the actually set content handler.
*
* @return the content handler
*/
public ContentHandler getContentHandler()
{
return contentHandler;
}
/**
* Sets the content handler. The object specified here will receive SAX
* events during parsing.
*
* @param handler the content handler
*/
public void setContentHandler(ContentHandler handler)
{
contentHandler = handler;
}
/**
* Returns the DTD handler. This class does not support DTD handlers,
* so this method always returns <b>null</b>.
*
* @return the DTD handler
*/
public DTDHandler getDTDHandler()
{
return null;
}
/**
* Sets the DTD handler. The passed value is ignored.
*
* @param handler the handler to be set
*/
public void setDTDHandler(DTDHandler handler)
{
}
/**
* Returns the entity resolver. This class does not support an entity
* resolver, so this method always returns <b>null</b>.
*
* @return the entity resolver
*/
public EntityResolver getEntityResolver()
{
return null;
}
/**
* Sets the entity resolver. The passed value is ignored.
*
* @param resolver the entity resolver
*/
public void setEntityResolver(EntityResolver resolver)
{
}
/**
* Returns the error handler. This class does not support an error handler,
* so this method always returns <b>null</b>.
*
* @return the error handler
*/
public ErrorHandler getErrorHandler()
{
return null;
}
/**
* Sets the error handler. The passed value is ignored.
*
* @param handler the error handler
*/
public void setErrorHandler(ErrorHandler handler)
{
}
/**
* 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
*/
public Object getProperty(String name)
{
return null;
}
/**
* 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
*/
public void setProperty(String name, Object value)
{
}
/**
* Returns the name to be used for the root element.
*
* @return the name for the root element
*/
public String getRootName()
{
return rootName;
}
/**
* Sets the name for the root element.
*
* @param string the name for the root element.
*/
public void setRootName(String string)
{
rootName = string;
}
/**
* 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(String name, Attributes attribs)
{
if (getException() == null)
{
try
{
Attributes at = (attribs == null) ? EMPTY_ATTRS : attribs;
getContentHandler().startElement(NS_URI, name, name, at);
}
catch (SAXException ex)
{
exception = ex;
}
}
}
/**
* Fires a SAX element end event.
*
* @param name the name of the affected element
*/
protected void fireElementEnd(String name)
{
if (getException() == null)
{
try
{
getContentHandler().endElement(NS_URI, name, name);
}
catch (SAXException ex)
{
exception = ex;
}
}
}
/**
* Fires a SAX characters event.
*
* @param text the text
*/
protected void fireCharacters(String text)
{
if (getException() == null)
{
try
{
char[] ch = text.toCharArray();
getContentHandler().characters(ch, 0, ch.length);
}
catch (SAXException ex)
{
exception = ex;
}
}
}
/**
* Returns a reference to an exception that occurred during parsing.
*
* @return a SAXExcpetion or <b>null</b> if none occurred
*/
public SAXException getException()
{
return exception;
}
/**
* 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();
}
}
/**
* Returns a reference to the configuration that is parsed by this object.
*
* @return the parsed configuration
*/
public abstract Configuration getParsedConfiguration();
/**
* Processes all keys stored in the actual configuration. This method is
* called by <code>parseConfiguration()</code> to start the main parsing
* process. <code>parseConfiguration()</code> calls the content handler's
* <code>startDocument()</code> and <code>endElement()</code> 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;
}
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