<![CDATA[]]>在XML中的含义是什么?

我经常在XML文件中发现这个奇怪的CDATA标签:

<![CDATA[some stuff]]>

我观察到这个CDATA标记总是出现在开头，然后跟着一些东西。

但有时用，有时不用。我假设这是为了标记一些东西是“数据”，将被插入之后。但是什么是数据呢?我用XML标记写的东西不是某种数据吗?

当前回答

Cdata是您可能希望传递给xml解析器但仍然不解释为xml的数据。

Say for eg :- You have an xml which has encapsulates question/answer object . Such open fields can have any data which does not strictly fall under basic data type or xml defined custom data types. Like --Is this a correct tag for xml comment ? .-- You may have a requirement to pass it as it is without being interpreted by the xml parser as another child element. Here Cdata comes to your rescue . By declaring as Cdata you are telling the parser don't treat the data wrapped as an xml (though it may look like one )

2013-11-19 19:12:02

其他回答

一个大的用例:你的xml包含一个程序，作为数据(例如Java的网页教程)。在这种情况下，您的数据包含大量字符，其中包括'&'和'<'，但这些字符并不是xml字符。

比较:

<example-code>
while (x &lt; len &amp;&amp; !done) {
    print( &quot;Still working, &apos;zzz&apos;.&quot; );
    ++x;
    }
</example-code>

with

<example-code><![CDATA[
while (x < len && !done) {
    print( "Still working, 'zzzz'." );
    ++x;
    }
]]></example-code>

Especially if you are copy/pasting this code from a file (or including it, in a pre-processor), it's nice to just have the characters you want in your xml file, w/o confusing them with XML tags/attributes. As @paary mentioned, other common uses include when you're embedding URLs that contain ampersands. Finally, even if the data only contains a few special characters but the data is very very long (the text of a chapter, say), it's nice to not have to be en/de-coding those few entities as you edit your xml file.

(我怀疑所有与评论的比较都有点误导/没有帮助。)

2014-05-28 13:26:19

Cdata是您可能希望传递给xml解析器但仍然不解释为xml的数据。

2013-11-19 19:12:02

CDATA代表字符数据。您可以使用它来转义某些字符，否则这些字符将被视为常规XML。其中的数据将不会被解析。例如，如果你想传递一个包含&的URL，你可以使用CDATA来实现。否则，您将得到一个错误，因为它将被解析为常规XML。

2012-05-10 04:52:52

CDATA节是“元素内容的一段，它被标记为仅供解析器解释为字符数据，而不是标记”。

在语法上，它的行为类似于注释:

<exampleOfAComment>
<!--
    Since this is a comment
    I can use all sorts of reserved characters
    like > < " and &
    or write things like
    <foo></bar>
    but my document is still well-formed!
-->
</exampleOfAComment>

．.．但它仍然是文件的一部分:

<exampleOfACDATA>
<![CDATA[
    Since this is a CDATA section
    I can use all sorts of reserved characters
    like > < " and &
    or write things like
    <foo></bar>
    but my document is still well formed!
]]>
</exampleOfACDATA>

尝试将以下内容保存为.xhtml文件(不是.html)，并使用FireFox(不是Internet Explorer)打开它，以查看注释和CDATA部分之间的差异;当你在浏览器中查看文档时，注释不会出现，而CDATA部分将:

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en" >
<head>
<title>CDATA Example</title>
</head>
<body>

<h2>Using a Comment</h2>
<div id="commentExample">
<!--
You won't see this in the document
and can use reserved characters like
< > & "
-->
</div>

<h2>Using a CDATA Section</h2>
<div id="cdataExample">
<![CDATA[
You will see this in the document
and can use reserved characters like
< > & "
]]>
</div>

</body>
</html>

使用CDATA节需要注意的一点是，它们没有编码，因此无法在其中包含字符串]]>。任何包含]]>的字符数据都必须-据我所知-是一个文本节点。同样地，从DOM操作的角度来看，你不能创建一个包含[]>的CDATA节:

var myEl = xmlDoc.getElementById("cdata-wrapper");
myEl.appendChild(xmlDoc.createCDATASection("This section cannot contain ]]>"));

这个DOM操作代码要么抛出一个异常(在Firefox中)，要么导致一个结构糟糕的XML文档:http://jsfiddle.net/9NNHA/

2010-05-06 20:35:12

通常用于在XML文档中嵌入自定义数据，如图片或声音数据。

2010-05-06 20:26:29

<![CDATA[]]>在XML中的含义是什么?

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