javaweb学习总结八(xml约束DTD)

一：XML约束概念

xml约束：可以编写一个文档来约束xml文件的书写规范。

xml语言格式比较严谨，不可能让程序员随意编写，所以必须要有约束。

二：常用的xml约束技术

1：DTD，document type definition

2：校验xml文件正当性

a：使用解析工具

b：使用ide工具，如：eclipse

books.html

 <?xml version="1.0" ?>
 <!DOCTYPE bookstore SYSTEM "book.dtd">
 <bookstore>
     <book>
         <name>Thinking in java</name>
         <author>Tom</author>
         <price>105.0</price>
     </book>
     <book>
         <name>Thinking in c</name>
         <author>Jack</author>
         <price>85.0</price>
     </book>
 </bookstore>

books.dtd

 <!ELEMENT bookstore(book+)>
     <!ELEMENT book(name,author,price)>
     <!ELEMENT name(#PCDATA)>
     <!ELEMENT author(#PCDATA)>
     <!ELEMENT price(#PCDATA)>

3:DTD约束有两种方式，一种作为单独的文件编写，也可以在XML文件内编写。

a：在XML文件内编写DTD

！DOCTYPE:定义约束  书架：根标签

b：外部引入DTD

<!DOCTYPE 书架 "books.dtd">

4:引用DTD约束

三：DTD约束语法细节

1：元素、属性、实体

2：元素定义

3：属性定义

使用ATTLIST设置属性，#REQUIRED  为必须的，  IMPLIED  为可选的

4：常用的属性值类型

a：ENUMERATED，枚举

b：ID

c：ENTITY,实体

引用实体：

参数实体：

四：案例分析

1:dtd约束文件

 <!DOCTYPE CATALOG [

 <!ENTITY AUTHOR "John Doe">
 <!ENTITY COMPANY "JD Power Tools, Inc.">
 <!ENTITY EMAIL "jd@jd-tools.com">

 <!ELEMENT CATALOG (PRODUCT+)>

 <!ELEMENT PRODUCT
 (SPECIFICATIONS+,OPTIONS?,PRICE+,NOTES?)>
 <!ATTLIST PRODUCT
 NAME CDATA #IMPLIED
 CATEGORY (HandTool|Table|Shop-Professional) "HandTool"
 PARTNUM CDATA #IMPLIED
 PLANT (Pittsburgh|Milwaukee|Chicago) "Chicago"
 INVENTORY (InStock|Backordered|Discontinued) "InStock">

 <!ELEMENT SPECIFICATIONS (#PCDATA)>
 <!ATTLIST SPECIFICATIONS
 WEIGHT CDATA #IMPLIED
 POWER CDATA #IMPLIED>

 <!ELEMENT OPTIONS (#PCDATA)>
 <!ATTLIST OPTIONS
 FINISH (Metal|Polished|Matte) "Matte"
 ADAPTER (Included|Optional|NotApplicable) "Included"
 CASE (HardShell|Soft|NotApplicable) "HardShell">

 <!ELEMENT PRICE (#PCDATA)>
 <!ATTLIST PRICE
 MSRP CDATA #IMPLIED
 WHOLESALE CDATA #IMPLIED
 STREET CDATA #IMPLIED
 SHIPPING CDATA #IMPLIED>

 <!ELEMENT NOTES (#PCDATA)>

 ]>

2：根据dtd写的CATELOG.xml

 <?xml version="1.0" encoding="utf-8" ?>
 <!DOCTYPE CATALOG SYSTEM "dtd/catelog.dtd">
 <CATALOG>
 <PRODUCT>
         <SPECIFICATIONS>water</SPECIFICATIONS>
         <PRICE>3.5</PRICE>
     </PRODUCT>
 </CATALOG>