org.apache.hadoop.hdfs.tools.offlineImageViewer.XmlImageVisitor Maven / Gradle / Ivy

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Apache Hadoop HDFS
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/**
 * 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.hadoop.hdfs.tools.offlineImageViewer;

import java.io.IOException;
import java.util.ArrayDeque;
import java.util.Deque;

import org.apache.hadoop.hdfs.util.XMLUtils;

/**
 * An XmlImageVisitor walks over an fsimage structure and writes out
 * an equivalent XML document that contains the fsimage's components.
 */
public class XmlImageVisitor extends TextWriterImageVisitor {
  final private Deque tagQ = new ArrayDeque<>();

  public XmlImageVisitor(String filename) throws IOException {
    super(filename, false);
  }

  public XmlImageVisitor(String filename, boolean printToScreen)
       throws IOException {
    super(filename, printToScreen);
  }

  @Override
  void finish() throws IOException {
    super.finish();
  }

  @Override
  void finishAbnormally() throws IOException {
    write("\n\n");
    super.finishAbnormally();
  }

  @Override
  void leaveEnclosingElement() throws IOException {
    if (tagQ.isEmpty()) {
      throw new IOException("Tried to exit non-existent enclosing element " +
          "in FSImage file");
    }

    ImageElement element = tagQ.pop();
    write("\n");
  }

  @Override
  void start() throws IOException {
    write("\n");
  }

  @Override
  void visit(ImageElement element, String value) throws IOException {
    writeTag(element.toString(), value);
  }

  @Override
  void visitEnclosingElement(ImageElement element) throws IOException {
    write('<' + element.toString() + ">\n");
    tagQ.push(element);
  }

  @Override
  void visitEnclosingElement(ImageElement element,
      ImageElement key, String value)
       throws IOException {
    write('<' + element.toString() + ' ' + key + "=\"" + value +"\">\n");
    tagQ.push(element);
  }

  private void writeTag(String tag, String value) throws IOException {
    write('<' + tag + '>' +
        XMLUtils.mangleXmlString(value, true) + "\n");
  }
}