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>