如果没有有效的网络连接，XML名称空间如何工作? [英] How do XML namespaces work without a working network connection?
问题描述
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.1.xsd">
<context:component-scan
base-package="com.springinaction.chapter01.knight" />
</beans>
上面的示例显示了具有多个名称空间的XML文件的示例.这些名称空间的目的是什么，最重要的是，即使没有Internet连接，它们为什么也可以工作?
The above example shows an example of an XML file with several namespaces. What is the purpose of these namespaces and most importantly why do they work even where there is no Internet connection?
我认为以xsi:schemaLocation开头的第二位包含用于验证XML文档结构的XML模式文件.如果我在不在网络上的计算机上运行使用此配置文件的应用程序，这些仍然如何工作? URL是否是JAR文件的别名?
I think the second bit that starts with xsi:schemaLocation contains the XML schema files which are used to validate the structure of the XML document. How come these still work if I run the application that uses this configuration file on a machine that is not on a network? Are the URLs somehow aliases to JAR files?
推荐答案
让我们假设我们有此XML文档.
Let us assume we have this XML document.
<?xml version="1.0" encoding="UTF-8"?>
<html>
<body>
Your text here
</body>
<body>
<height>182 cm</height>
<weight>83 kg</weight>
</body>
</html>
它包括HTML，该HTML的body标记具有HTML渲染器的语义.它还具有另一个带有有关特定人的信息的身体标签.名称空间定义了此标签的语义范围.没有名称空间(如提供的示例中所示)，解析器无法分辨出差异，因为它们在语法上是相同的.
It includes HTML which has a body tag with a semantic meaning for a HTML renderer. It also has another body tag which carries information about a specific person. A namespace defines a semantic scope for this tag. Without a namespace(as in the example provided), it is impossible for a parser to tell the difference because they are syntactically the same.
以下是同一文档的语义正确版本:
Here is the semantically correct version of the same document:
<?xml version="1.0" encoding="UTF-8"?>
<html:html xmlns:html="http://www.w3.org/TR/xhtml1/">
<html:body>
Your text here
</html:body>
<human:body xmlns:html="http://www.example.com/human/">
<human:height>182 cm</human:height>
<human:weight>83 kg</human:weight>
</human:body>
</html:html>
因此，由于有了命名空间，我们不必担心具有不同含义的冲突标签.
Thus thanks to namespaces we do not have worry about conflicting tags with different meanings.
名称空间URI本身从未真正解析过，并且是任意的(因此您可以脱机使用它们).
The namespace URIs themselves are never actually resolved, and are arbitrary (thus you can use them offline).
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