Java Web

将约束的规则定义在外部的dtd文件中

本地：&lt;!DOCTYPE&nbsp;根标签名&nbsp;<b>SYSTEM</b>&nbsp;"dtd文件的位置"&gt;

网络：&lt;!DOCTYPE&nbsp;根标签名&nbsp;<b>PUBLIC&nbsp;</b>"dtd文件名字(随便起)"&nbsp;"dtd文件的位置URL"&gt;

将约束规则定义在xml文档中

&lt;?xml&nbsp;version="1.0"&nbsp;encoding="UTF-8"&nbsp;?&gt;<br>&lt;!DOCTYPE&nbsp;students [<br>&lt;!ELEMENT&nbsp;students&nbsp;(student*)&nbsp;&gt;<br>&lt;!ELEMENT&nbsp;student&nbsp;(name,age,sex)&gt;<br>&lt;!ELEMENT&nbsp;name&nbsp;(#PCDATA)&gt;<br>&lt;!ELEMENT&nbsp;age&nbsp;(#PCDATA)&gt;<br>&lt;!ELEMENT&nbsp;sex&nbsp;(#PCDATA)&gt;<br>&lt;!ATTLIST&nbsp;student&nbsp;number&nbsp;ID&nbsp;#REQUIRED&gt;<br>]&gt;<br><br>&lt;students&gt;<br>&nbsp; &nbsp; &nbsp; &lt;student&nbsp;number="itcast_0001"&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &lt;name&gt;tom&lt;/name&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &lt;age&gt;18&lt;/age&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &lt;sex&gt;male&lt;/sex&gt;<br>&nbsp; &nbsp; &nbsp; &lt;/student&gt;<br>&lt;/students&gt;

xmlns: xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.itcast.cn/xml&nbsp;&nbsp;student.xsd"

什么都不写默认空前缀<br>xmlns="http://www.itcast.cn/xml"

a标识，使用任何标签都要引入这个a前缀<br>xmlns:a ="http://www.itcast.cn/xml"

&lt;a:students&nbsp;&nbsp;&nbsp;xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;xsi:schemaLocation="<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;http://www.aaa.cn/xml&nbsp;&nbsp;<b>student1.xsd</b><br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;http://www.bbb.cn/xml&nbsp;&nbsp;<b>student2.xsd</b>"&nbsp; &nbsp;两个约束文档<br>&nbsp; &nbsp; &nbsp; &nbsp; <b>&nbsp;xmlns:a</b>="http://www.itcast.cn/xml"<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<b>xmlns:b</b>="http://www.itcast.cn/xml"<br>&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&lt;a:student&nbsp;number="heima_0001"&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&lt;a:name&gt;tom&lt;/a:name&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&lt;a:age&gt;18&lt;/a:age&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&lt;a:sex&gt;male&lt;/a:sex&gt;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&lt;/a:student&gt;<br>&nbsp;&lt;/a:students&gt;