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     */
018    package org.apache.hadoop.hdfs.tools.offlineImageViewer;
019    
020    import java.io.IOException;
021    import java.util.LinkedList;
022    
023    import 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     */
028    public 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    }