001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.tools.offlineImageViewer;
019
020import java.io.IOException;
021import java.util.LinkedList;
022
023import org.apache.hadoop.hdfs.util.XMLUtils;
024/**
025 * An XmlImageVisitor walks over an fsimage structure and writes out
026 * an equivalent XML document that contains the fsimage's components.
027 */
028public class XmlImageVisitor extends TextWriterImageVisitor {
029  final private LinkedList<ImageElement> tagQ =
030                                          new LinkedList<ImageElement>();
031
032  public XmlImageVisitor(String filename) throws IOException {
033    super(filename, false);
034  }
035
036  public XmlImageVisitor(String filename, boolean printToScreen)
037       throws IOException {
038    super(filename, printToScreen);
039  }
040
041  @Override
042  void finish() throws IOException {
043    super.finish();
044  }
045
046  @Override
047  void finishAbnormally() throws IOException {
048    write("\n<!-- Error processing image file.  Exiting -->\n");
049    super.finishAbnormally();
050  }
051
052  @Override
053  void leaveEnclosingElement() throws IOException {
054    if(tagQ.size() == 0)
055      throw new IOException("Tried to exit non-existent enclosing element " +
056                "in FSImage file");
057
058    ImageElement element = tagQ.pop();
059    write("</" + element.toString() + ">\n");
060  }
061
062  @Override
063  void start() throws IOException {
064    write("<?xml version=\"1.0\" ?>\n");
065  }
066
067  @Override
068  void visit(ImageElement element, String value) throws IOException {
069    writeTag(element.toString(), value);
070  }
071
072  @Override
073  void visitEnclosingElement(ImageElement element) throws IOException {
074    write("<" + element.toString() + ">\n");
075    tagQ.push(element);
076  }
077
078  @Override
079  void visitEnclosingElement(ImageElement element,
080      ImageElement key, String value)
081       throws IOException {
082    write("<" + element.toString() + " " + key + "=\"" + value +"\">\n");
083    tagQ.push(element);
084  }
085
086  private void writeTag(String tag, String value) throws IOException {
087    write("<" + tag + ">" +
088        XMLUtils.mangleXmlString(value, true) + "</" + tag + ">\n");
089  }
090}