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The Java API for extending the main Guacamole web application. This
is not needed for authoring a new Guacamole-based web application.
/*
* 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.guacamole.xml;
import java.util.Deque;
import java.util.LinkedList;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
/**
* A simple ContentHandler implementation which digests SAX document events and
* produces simpler tag-level events, maintaining its own stack for the
* convenience of the tag handlers.
*/
public class DocumentHandler extends DefaultHandler {
/**
* The name of the root element of the document.
*/
private String rootElementName;
/**
* The handler which will be used to handle element events for the root
* element of the document.
*/
private TagHandler root;
/**
* The stack of all states applicable to the current parser state. Each
* element of the stack references the TagHandler for the element being
* parsed at that level of the document, where the current element is
* last in the stack, and the root element is first.
*/
private Deque stack =
new LinkedList();
/**
* Creates a new DocumentHandler which will use the given TagHandler
* to handle the root element.
*
* @param rootElementName The name of the root element of the document
* being handled.
* @param root The TagHandler to use for the root element.
*/
public DocumentHandler(String rootElementName, TagHandler root) {
this.root = root;
this.rootElementName = rootElementName;
}
/**
* Returns the current element state. The current element state is the
* state of the element the parser is currently within.
*
* @return The current element state.
*/
private DocumentHandlerState getCurrentState() {
// If no state, return null
if (stack.isEmpty())
return null;
return stack.getLast();
}
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
// If the SAX implementation does not provide the local name, the
// qualified name should be used instead
String name = localName.isEmpty() ? qName : localName;
// Get current state
DocumentHandlerState current = getCurrentState();
// Handler for tag just read
TagHandler handler;
// If no stack, use root handler
if (current == null) {
// Validate element name
if (!name.equals(rootElementName))
throw new SAXException("Root element must be '" + rootElementName + "'");
handler = root;
}
// Otherwise, get handler from parent
else {
TagHandler parent_handler = current.getTagHandler();
handler = parent_handler.childElement(name);
}
// If no handler returned, the element was not expected
if (handler == null)
throw new SAXException("Unexpected element: '" + name + "'");
// Initialize handler
handler.init(attributes);
// Append new element state to stack
stack.addLast(new DocumentHandlerState(handler));
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
// Pop last element from stack
DocumentHandlerState completed = stack.removeLast();
// Finish element by sending text content
completed.getTagHandler().complete(
completed.getTextContent().toString());
}
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
// Get current state
DocumentHandlerState current = getCurrentState();
if (current == null)
throw new SAXException("Character data not allowed outside XML document.");
// Append received chunk to text content
current.getTextContent().append(ch, start, length);
}
/**
* The current state of the DocumentHandler.
*/
private static class DocumentHandlerState {
/**
* The current text content of the current element being parsed.
*/
private StringBuilder textContent = new StringBuilder();
/**
* The TagHandler which must handle document events related to the
* element currently being parsed.
*/
private TagHandler tagHandler;
/**
* Creates a new DocumentHandlerState which will maintain the state
* of parsing of the current element, as well as contain the TagHandler
* which will receive events related to that element.
*
* @param tagHandler The TagHandler which should receive any events
* related to the element being parsed.
*/
public DocumentHandlerState(TagHandler tagHandler) {
this.tagHandler = tagHandler;
}
/**
* Returns the mutable StringBuilder which contains the current text
* content of the element being parsed.
*
* @return The mutable StringBuilder which contains the current text
* content of the element being parsed.
*/
public StringBuilder getTextContent() {
return textContent;
}
/**
* Returns the TagHandler which must handle any events relating to the
* element being parsed.
*
* @return The TagHandler which must handle any events relating to the
* element being parsed.
*/
public TagHandler getTagHandler() {
return tagHandler;
}
}
}