hadoop XmlImageVisitor 源码
haddop XmlImageVisitor 代码
文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/XmlImageVisitor.java
/**
* 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<ImageElement> 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<!-- Error processing image file. Exiting -->\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("</" + element.toString() + ">\n");
}
@Override
void start() throws IOException {
write("<?xml version=\"1.0\" ?>\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) + "</" + tag + ">\n");
}
}
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