XML learning:
1. xml introduction and Syntax:
2. xml constraints:
DTD
Schema
3. XML parsing: (***** Focus)
XML:
What: Extensible Markup Language (Extensible Markup Language .) <Dog> </dog>
* HTML: hypertext markup language. markup language: some tags are available. <HTML> Why:
* It is used to process a large amount of related data.
Where:
* Used as the software configuration file (SSH --- all configuration files are XML)
* Used to store data (as a small database)
* Used for asynchronous system data transmission.
How:
XML Syntax:
Document declaration: (at first glance)
* Note: the location where the document declaration appears. The position of the first column in the first line of XML.
<? XML version = "1.0"?>
Version: Version 1.0 and the version attribute is required.
Encoding: Optional attribute of the sequence set
Standalone: whether other documents are required. Yes/No
<? XML version = "1.0" encoding = "UTF-8" standalone = "yes"?>
Elements: (important)
Element: tag.
Tag Syntax:
<Span> </span>
Label nesting:
Must be correctly nested
<A> <B> </a> </B> --- incorrect
<A> <B> </B> </a> --- correct
XML must have only one tag.
Element naming rules:
* Case sensitive.
* It cannot start with a number or _.
* It cannot start with XML.
* The element name cannot contain spaces or colons.
<A> <person>...
Attribute: (important)
<Input type = "" name = ""> input: Both element (TAG) type and name are called attributes.
<Input>
<Type> </type>
<Name> </Name>
</Input>
Note: (not always)
Note: <! -- Comment content -->
* *** NOTE: Annotations cannot be nested. Annotations cannot be written before the document declaration.
Special characters and CDATA area: (it will be displayed at a Glance)
Escape characters:
<Span> 3 <5 </span>
<& Lt;
> & Gt;
& Amp;
"& Quot;
'& Apos;
CDATA zone: --- expand something: it is not considered as a tag, it is considered as a common text (string ).
<! [CDATA [think it is a common text]>
* Statement <! [CDATA []>
Processing Command (PI): (I forgot after reading it)
* <? XML-stylesheet type = "text/CSS" href = "1.css"?>
Replacing HTML with XML: XML syntax is complicated. xhmtl ---- HTML5 ---
========================================================== ========================================================== ==========================================
Develop a framework:
Configuration File: What are the advantages of a file: you do not need to modify the source code of the program.
Properties: Used as the software configuration file.
Key = value ---- format file.
Com. login. = cn. itcast. Test
XML: Used as the software configuration file.
XML can better describe the hierarchical relationship.
<Web-app>
<Servlet>
<Servlet-Name> </servlet-Name>
</Servlet>
</Web-app>
Because XML is a scalable Markup Language
<Web-app>
<Servlet>
<Cat> </CAT>
<Servlet-Name> </servlet-Name>
</Servlet>
</Web-app>
XML constraints: DTD and XML Schema (mainly understood)
(***** What are the XML constraints? What is the difference ?)
XML followed by the XML Syntax: well-formed XML.
The XML syntax is followed by the constraints document definition: Valid XML
DTD: Document Type Definition:
Use DTD to constrain XML documents. Quick Start.
To write a DTD, follow these steps:
1. What labels and quantities are required in the XML document? Six
<! Element element name element type>
2. query what type is in the XML element.
Simple or complex
3. You need to introduce DTD in XML.
The method of introducing DTD:
Internal document
<! Doctype bookshelf [
<! Element bookshelf (Book +)>
<! Element book (title, author, price, introduction)>
<! Element name (# pcdata)>
<! Element author (# pcdata)>
<! Price of element (# pcdata)>
<! Element introduction (# pcdata)>
]>
Document external
* Local
<! Doctype bookshelf System "book. DTD">
* Network
<! Doctype bookshelf public "DTD name" "DTD path">
DTD Syntax:
Element Definition
Syntax: <! Element element name element type>
Element type:
# Pcdata: parsed character data
Child element:
Empty: Empty Element
Any: Any element
Number of child elements
+: One or more times
*: Zero or multiple times
? : Zero or one
Subelement order
,: Sub-elements must appear in order.
|: The child element is in the or relationship.
Attribute definition: attribute -- attribute
Syntax: <! ATTLIST element name attribute type attribute constraint>
* <! ATTLIST Book Publishing House CDATA # required>
Property type:
CDATA: character data (string)
Enumeration: Enumeration type
ID: unique
Property constraints:
# Required: the attribute must appear.
# Implied: the attribute is optional.
# Fixed: the attribute uses a fixed value.
Default Value:
Entity Definition
Syntax: <! Entity Object Name entity value>
<! Entity bookname "sunflower Collection">
========================================================== ========================================================== ==========================================
XML programming (emphasis...) crud
XML parsing technology?
(***** What are the XML parsing technologies? What is the difference ?)
* *** XML parsing techniques are commonly used in Dom and sax.
DOM: Document Object Model. load XML into the memory at a time to form a tree structure.
Sax: Simple API for XML. You do not need to load documents to the memory at a time, read and parse documents, and use event-driven methods.
JAXP: Sun. Provided API.
1. Create an XML parser.
2. Use the parser to parse XML --- document.
3. Use document to get the nodes for the operation.
Crud.
Sax: event-driven method. parse while reading.
// Create a parser
// Processor.
* *** Dom4j: an open-source organization. (important)
XPath: nodes that facilitate XML query. dom4j supports XPath.
JDOM: open-source organization.
XML concepts, constraints, and notes
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