1.1 Introduction to xml
- a) xml, eXtensible Markup Language, is a markup language.
- b) xml is a A very flexible language, no fixed tags, all tags can be customized.
- c) Usually, xml is used for information recording and transmission. Therefore, xml is often used as a configuration file .
1.2 Well-formed xml
- a) Declaration information, used to describe the version and encoding of xml
- b) xml has one and only one root element
- c) xml is case sensitive
- d) tag They are in pairs, and they must be nested correctly.
- e) Use double quotes for attribute values
For example:
xml version="1.0" encoding="UTF-8" ?>
<books >
<book id="b01">
<name >java advanced programmingname>
<author >Zhang Sanauthor>
<price >50.5price>
book>
<book id="b02">
<name >java intermediate programmingname>
<author >Li Siauthor>
<price >30.5price>
book>
books>
2. DTD
2.1 Introduction to DTD
a) DTD, Document Type Definition, Document Type Definition
b) DTD is used to constrain xml The document format of xml is guaranteed to be a valid xml.
c) DTD can be divided into two types, internal DTD, external DTD
2.2 Use DTD 2.2.1 Definition of internal DTD
a ) The syntax is as follows:
b) Element declaration syntax:
c) Quantifier
> +: means one or more occurrences, at least once
> ?: means 0 or 1 occurrence
> *: means any number of occurrences
d) Attribute declaration syntax:
> Attribute Type: CDATA, character data (character data)
> Default value:
- #REQUIRED, which means must appear
- #IMPLIED, which means it is not necessary
e) Complete xml code with DTD:
< span style="color: #ff00ff;">xml version="1.0" encoding="UTF-8"?>
DOCTYPE scores [>
ELEMENT student (name, course, score)>
ATTLIST student id CDATA #REQUIRED>
ELEMENT name (#PCDATA)>
ELEMENT course (#PCDATA)>
ELEMENT score (#PCDATA)> ]>
<scores>
<student id="1">
<name >Wang Tongname>
<course >javacourse>
<score >89score>
student>
<student id="2">
<name >Li Jianame>
<course >sqlcourse>
<score >58score>
student>
scores>
2.2.2 Definition of external DTD
a) Create an independent dtd file
xml version="1.0" encoding="UTF-8"?>
ELEMENT scores (student+)>
ELEMENT student (name, course, score)>
ATTLIST student id CDATA #REQUIRED>
ELEMENT name (#PCDATA)>
ELEMENT course (#PCDATA)>
ELEMENT score (#PCDATA)>
b) Import external DTD files in xml
<books >
<book id="b01">
<name >java advanced programmingname>
<author >Zhang Sanauthor>
<price >50.5price>
book>
<book id="b02">
<name >java intermediate programmingname>
<author >Li Siauthor>
<price >30.5price>
book>
books>
xml version="1.0" encoding="UTF-8"?>
DOCTYPE scores [>
ELEMENT student (name, course, score)>
ATTLIST student id CDATA #REQUIRED>
ELEMENT name (#PCDATA)>
ELEMENT course (#PCDATA)>
ELEMENT score (#PCDATA)> ]>
<scores>
<student id="1">
<name >Wang Tongname>
<course >javacourse>
<score >89score>
student>
<student id="2">
<name >Li Jianame>
<course >sqlcourse>
<score >58score>
student>
scores>
xml version="1.0" encoding="UTF-8"?>
ELEMENT scores (student+)>
ELEMENT student (name, course, score)>
ATTLIST student id CDATA #REQUIRED>
ELEMENT name (#PCDATA)>
ELEMENT course (#PCDATA)>
ELEMENT score (#PCDATA)>
DOCTYPE scores SYSTEM "scores.dtd">