我继承了一个数据存储,它使用简单的文本文件来保存文档。
文档具有一些属性(日期、标题和文本),这些属性被编码在文件名中:
然而实际上系统中的文档有更多的属性,并且再次建议添加更多属性。
切换到 XML 格式似乎是合乎逻辑的,我已经这样做了,现在每个文档都编码在它自己的 XML 文件中。
但是,从 XML 读取文件现在速度慢得离谱! (以前 2000 篇 .txt 格式的文章需要几秒钟,现在 2000 篇 .xml 格式的文章需要 10 多分钟)。
我之前使用 DOM 解析器,在发现读取速度有多慢后,我切换到 SAX 解析器,但它仍然一样慢(嗯,更快,但仍然需要 10 分钟)。
XML 就是这么慢吗,还是我做了一些奇怪的事情?任何想法将不胜感激。
该系统是用JavaSE 1.6编写的。 解析器是这样创建的:
/*
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
*/
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser;
try {
saxParser = factory.newSAXParser();
ArticleSaxHandler handler = new ArticleSaxHandler();
saxParser.parse(is, handler);
return handler.getArticle();
} catch (ParserConfigurationException e) {
throw new IOException(e);
} catch (SAXException e) {
throw new IOException(e);
} finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
logger.error(e);
}
}
}
}
private class ArticleSaxHandler extends DefaultHandler {
private URI uri = null;
private String source = null;
private String author = null;
private DateTime articleDatetime = null;
private DateTime processedDatetime = null;
private String title = null;
private String text = null;
private ArticleElement currentElement;
private final StringBuilder builder = new StringBuilder();
public Article getArticle() {
return new Article(uri, source, author, articleDatetime, processedDatetime, title, text);
}
/** Receive notification of the start of an element. */
public void startElement(String uri, String localName, String qName, Attributes attributes) {
if (builder.length() != 0) {
throw new RuntimeException(new SAXParseException(currentElement + " was not finished before " + qName + " was started", null));
}
currentElement = ArticleElement.getElement(qName);
}
public void endElement(String uri, String localName, String qName) {
final String elementText = builder.toString();
builder.delete(0, builder.length());
if (currentElement == null) {
return;
}
switch (currentElement) {
case ARTICLE:
break;
case URI:
try {
this.uri = new URI(elementText);
} catch (URISyntaxException e) {
throw new RuntimeException(e);
}
break;
case SOURCE:
source = elementText;
break;
case AUTHOR:
author = elementText;
break;
case ARTICLE_DATE_TIME:
articleDatetime = getDateTimeFormatter().parseDateTime(elementText);
break;
case PROCESSED_DATE_TIME:
processedDatetime = getDateTimeFormatter().parseDateTime(elementText);
break;
case TITLE:
title = elementText;
break;
case TEXT:
this.text = elementText;
break;
default:
throw new IllegalStateException("Unexpected ArticleElement: " + currentElement);
}
currentElement = null;
}
/** Receive notification of character data inside an element. */
public void characters(char[] ch, int start, int length) {
builder.append(ch, start, length);
}
public void error(SAXParseException e) {
fatalError(e);
}
public void fatalError(SAXParseException e) {
logger.error("currentElement: " + currentElement + " ||builder: " + builder.toString() + "\n\n" + e.getMessage(), e);
}
}
private enum ArticleElement {
ARTICLE(ARTICLE_ELEMENT_NAME), URI(URI_ELEMENT_NAME), SOURCE(SOURCE_ELEMENT_NAME), AUTHOR(AUTHOR_ELEMENT_NAME), ARTICLE_DATE_TIME(
ARTICLE_DATETIME_ELEMENT_NAME), PROCESSED_DATE_TIME(PROCESSED_DATETIME_ELEMENT_NAME), TITLE(TITLE_ELEMENT_NAME), TEXT(TEXT_ELEMENT_NAME);
private String name;
private ArticleElement(String name) {
this.name = name;
}
public static ArticleElement getElement(String qName) {
for (ArticleElement element : ArticleElement.values()) {
if (element.name.equals(qName)) {
return element;
}
}
return null;
}
}
最佳答案
从无缓冲的流中读取数据可以解释这些性能问题。这与从文本到 XML 的更改没有直接关系,但也许您的新实现碰巧不再使用 BufferedInputStream
。
按照该路径,详细检查此 is
是否已缓冲:
saxParser.parse(is, handler);
关于java - 加载 XML 非常慢,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3521064/