Table of contents
2.1 Add DTD declaration to XML
2.2 Classification of elements
Four. The difference between XML and JSON
One.XML
What is well-formed XML
Well-formed XML is an XML document that follows all the " Rules for XML Documents "
The role of XML
①Data interaction
② Make configuration
standard XML format
- has one and only one element
- XML tag case is correctly distinguished
- Use closing tags correctly
- Nest tags correctly
- A valid tag name is used
- define valid properties
2. Element definition
2.1 Add DTD declaration to XML
<!DOCTYPE root[]>
2.2 Classification of elements
<ELEMENT element-name EMPTY>//empty element
<ELEMENT element-name (#PCDATA)>//text element
<ELEMENT element-name (e1,e2)>//mixed element
2.3 Restrictions on elements
and (,) not (|)
Times: ①0 or 1:?
②0~N:*
③1~N：+
3. Attribute definition
grammar
<!ATTLIST element-name att_name type desc>
attribute type type
- ID
- CDATA
- IDREF
- reference
attribute description
- #REQUIRED: required
- #IMPLIED: optional
- Default value Note: only when the type is (male|female) type, desc can use the default value
For example:
<?xml version="1.0" encoding="UTF-8"?>
<!--
config tag: can contain 0~N action tags
-->tdt解析
<!DOCTYPE config[
<!ELEMENT config (action+)>
<!ELEMENT action (forward*)
<!ATTLIST action
path CDATA #REQUIRED
type CDATA #REQUIRED
>
<!ATTLIST forward
name CDATA #REQUIRED
path CDATA #REQUIRED
redirect (true|false) 'false'
>
]>
<config>
<!--
action tag: can contain 0~N forward tags path: a string starting with /, and the value must be unique and non-empty, the path corresponding to the sub-controller type: string, non-empty, the full class name of the sub-controller --> <action path="/registerAction" type="test.action.RegisterAction"> <forward name="success" path="/index.jsp" redirect="true" /> <forward name="forward name="success" path="/index.jsp" redirect="true" /> ="failed" path="/register.jsp" redirect="false" /> </action> <action path="/loginAction" type="test.action.LoginAction"> <forward name="
a
"
path
=
"
/
index
.jsp" redirect="false" />
<forward name="b" path="/welcome.jsp" redirect="true" />
</action>
</config>
Four. The difference between XML and JSON
Both XML and JSON are markup languages for data exchange, and they have some differences in syntax and usage:
Syntax structure : XML uses tags while JSON uses brackets.
Data types : XML supports custom data types, while JSON only supports string, number, boolean, array, and object data types.
Readability : XML is easier for humans to read and understand than JSON.
Processing efficiency : JSON is lighter and faster than XML, because JSON does not need redundant tags to describe data like XML.
In general, XML is suitable for complex data structures while JSON is suitable for simple and lightweight data exchange.
5. Mind map
