What is it?

Source: Internet
Author: User
Tags xml parser
    • There are 5 predefined entity references in XML:

When I was working on a project today, I always reported an error when I wrote Js in the file. Later I found that it was in JS. The solution was to put Js in the file! [CDATA []>. Now let's take a look.<! [CDATA []> what is it.

The following content is transferred from: http://www.w3school.com.cn/xml/xml_cdata.asp


The text in all XML documents will be parsed by the parser.

Only the text in the CDATA section is ignored by the parser.


Pcdata indicatesResolved character data(Parsed character data ).

The XML Parser parses all the text in the XML document.

When an XML element is parsed, the text between tags is also parsed:

<Message> this article will also be parsed </message>

In this example, the <Name> element contains two other elements (first and last ):

<Name> <first> Bill </first> <last> Gates </last> </Name>

The parser will break it into sub-elements like this:

<Name> <first> Bill </first> <last> Gates </last> </Name>
Escape characters

Invalid xml characters must be replaced with entity reference ).

If you place a character similar to "<" in the XML document, this document produces an error because the parser interprets it as the beginning of a new element. Therefore, you cannot write as follows:

<Message> If salary <1000 then </message>

To avoid such errors, replace the character "<" with the entity reference, as shown in the following figure:

<Message> If salary <1000 then </message>
There are 5 predefined entity references in XML:
& Lt; < Less
& Gt; > Greater
& Amp; & And number
& Apos; ' Ellipsis
& Quot; " Quotation marks

Note:Strictly speaking, it is invalid to have only the characters "<" and "&" in XML. Ellipsis, quotation marks, and greater than signs are valid, but it is a good habit to replace them with Entity references.


The term CDATA refers to text data that should not be parsed by the XML Parser (unparsed character data ).

"<" And "&" are invalid in XML elements.

"<" Produces an error because the parser interprets the character as the beginning of the new element.

"&" Also produces errors because the parser interprets the character as the beginning of the character entity.

Some text, such as JavaScriptCode, Contains a large number of "<" or "&" characters. To avoid errors, you can define the script code as CDATA.

All content in the CDATA section is ignored by the parser.

CDATA is partly composed"<! [CDATA ["Start,"]>"End:

<SCRIPT> <! [CDATA [function matchwo (a, B) {if (a <B & A <0) Then {return 1 ;}else {return 0 ;}]]> </SCRIPT>

In the preceding example, the parser ignores all content in the CDATA section.

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