-- Author: Xiaoye
-- Release Date: 22:46:00-- XML practical tutorial
First, let's ask a question.
About JS and XML
I used js to generate an XSL code, such<XSL: For-each select = "mycomputer/computer"> <XSL: value-of select = "cpu1"/> This 1 is dynamically generated. I saved the <XSL: value-of select = "cpu1"/> statement with a variable in JS and want to insert it into XSL, how can I write code? |
XML practical tutorial
Extensible Markup Language (XML) is a descriptive language composed of a series of rules. It is essentially a definition language. Any industry can follow these rules to define various identifiers, describe the elements in the information, and then process the information through the analysis program, so that the information can be "self-described ".
XML is an ideal language for large and complex documents. It not only allows you to specify words in a document, but also allows you to specify relationships between elements. With the development of the network, XML's position in network development has gradually caught up with HTML, and many browsers have supported XML well. XML is becoming a mainstream language for the future development of the network.
1. xml Overview
1. What is XML
XML has different interpretations from different perspectives, as described below:
(1) XML is a type of markup language, which means that developers can customize any tag that complies with the rules as needed, while HTML is only a pre-defined markup language, only defined tags can be parsed. Custom tags cannot be parsed.
(2) XML is a semantic structured language that reasonably describes the structure and semantics of a file.
(3) XML is a common data format and a simple data format consisting of plain ASCII text. Therefore, XML is highly destructive.
(4) from an advanced perspective, XML is a self-describing language.
2. Common Terms of XML
(1) DTD (Document Type Definition): defines the file type. The defined content includes the labels that can be used, the way tag elements are nested, and the processing method. The XML standard does not force the tag designer to use the DTD. However, most new languages developed based on XML carry the DTD, which makes it easier for developers to write understandable tags and compile clever software.
(2) XML file: the XML file consists of DTD and XML text. simple XML text does not contain DTD.
(3) XSL and CSS: XML can define information content, but cannot define the representation of information. XML converts information through XSL (XML style language, XML style language) and CSS (Cascading Style Sheet.
(4) XML Schema: although the DTD limits the use of tags, automatic XML processing still requires more rigorous and comprehensive tools, resulting in XML schema.
(5) Dom (Document Object Model): A file object model. It converts the content of an XML file into an object model and provides an interface for the application to access the XML file.
(6) XSLT (XML Stylesheet Language Transformation): the XML style conversion language. XSLT extracts the required data from a defined XML file and forms it in different forms.
(7) xpointer and xlinks: xpointer and xlinks are similar to hyperlinks in HTML and used to link other XML files or parts of XML files.
(8) XML framework: the XML framework is used to control the structure of XML files. It is a high-level structure control.
Ii. XML syntax explanation
1. xml file structure
As mentioned above, XML allows custom tags to describe information visually. If you need to describe the basic configurations of a computer, you can customize some easy-to-understand tags, such as "computer" and "CPU. By using these tags, the basic configuration of a computer is described as follows in XML:
<Computer>
<CPU> P4 </CPU>
<Ram> 256 m </Ram>
<Harddisk> 80 GB </Computer>
The above content can be quickly understood by readers with a little computer knowledge, which is also the advantage of XML. Of course, you also need to add "<? XML version = "1.0"?>" To indicate the XML version used by the file. XML declaration is a processing command. The complete XML declaration example is as follows:
<? XML version = "1.0" encoding = "gb2312" standalone = "no"?>
The declaration must contain the "version" attribute, which is used to set the XML version number used and must be the first in the attribute list. The "standalone" attribute indicates whether the XML document is used together with an external document type definition DTD. The "encoding" attribute sets the encoding standard used by the data.
XML files usually start with XML declarations and use XML elements to organize data. XML elements include tag and character data. To make data organization easier and clearer, you can add CDATA data blocks to character data and add annotations.
To sum up, we can get the basic structure of the XML file, as described below:
(1) The XML file starts with an XML declaration.
(2) process the command with "<?" Start with "?>" End, "<?" The first word is the Processing Instruction name.
(3) The custom tag contains the "<" and ">" characters. The tag must appear in pairs. The last tag must start with "<.
(4) XML elements can contain body and other elements, but must be strictly nested. That is, each start tag must have a corresponding end tag.
(5) XML elements cannot overlap.
XML files are plain text files that can be compiled using any text editor. For example, if you save the XML file configured on the computer with the "XML" extension in the text editor and browse the file in IE browser later than version 5.0, the result is as shown in <a href = 'H: /data/PIC/60090405a.jpg 'target = PIC> figure </a> 1:
2. xml file elements
The elements of an XML file are extensible and associated with each other. The naming rules of elements are very simple, as described below:
(1) XML Element Scalability:
The XML file can be expanded to save more information. For example, you can add the display content to the XML file of the basic computer configuration described above, simply add the "Monitor" tag to the original XML file, as follows:
<? XML version = "1.0" encoding = "gb2312" standalone = "no"?>
<Computer>
<CPU> P4 </CPU>
<Ram> 256 m </Ram>
<Harddisk> 80 GB <Monitor> Philips 107 TB </monitor>
</Computer>
(2) XML elements are associated with each other:
The relationship between XML elements is like a tree composed of the same node. Each node has the concept of "brother" or "Parent and Child". In the preceding Computer Configuration XML file, "computer" is the root element. "CPU", "Ram", and "harddisk" are all subelements of "computer. Conversely, "computer" is the parent element of "CPU" and "Ram. "CPU" and "Ram" are brother elements because their parent elements are the same.
(3) XML elements are case sensitive:
XML elements are case sensitive. Therefore, "<computer>" and "<computer>" are different elements.
(4) expression of an empty element:
XML indicates that an empty element is very convenient. A label ends with a "/>" symbol to indicate an empty element.
(5) reserved characters of XML elements:
Some characters are part of the XML syntax structure. To reference XML data, they must be replaced by special characters, as shown in the following table:
(<A href = 'H:/data/PIC/60090405b.jpg 'target = PIC> figure </a>)
(6) uniqueness of the root element:
Each XML file must have a unique root element, as shown in the preceding Computer Configuration XML file. "Computer" is the unique root element of the XML file.
(7) element content:
XML elements contain different content types. An XML element consists of all content between the start and end tags of an element. An element can contain element content, mixed content, simple content, and empty content. It can also contain attributes.
(8) element naming:
The naming rules that XML elements must follow are described as follows:
The name can contain letters, numbers, and other letters (such as Chinese characters). The name cannot start with a number or underline. The name cannot start with the letter "XML" (or XML, XML, etc; the name cannot contain spaces. ":" cannot be used in the name because it is reserved by namespaces.
Some tips for customizing element names are as follows:
The name should be descriptive and can be underlined to make the name more vivid; the name is not too long; Because XML files are usually connected to the database, therefore, it is recommended that the Field name of the Database correspond to the element name of the XML file. Non-English letters are legal in the XML element name, but depend on whether the parser supports it.
3. xml attributes
Similar to HTML markup, XML elements can also design attributes in their starting markup to provide additional information about elements. The information provided by an attribute is generally not a component of data.
Attribute values must be enclosed in quotation marks, and single and double quotation marks can be used. For example, you can add a user attribute to the "computer" mark of the XML file for the computer, as shown below:
<Computer user = "Ma Qian Xue">
In single and double quotation marks, double quotation marks are commonly used. If the attribute value itself contains quotation marks, single quotation marks must be used.
4. CDATA mark
Under the CDATA tag, all tags or object references are ignored by the XML Parser and processed as characters. The CDATA mark syntax is as follows:
<! [CDATA [
Text Content
]>
The text content in the CDATA tag cannot contain the string "]>", and the CDATA tag cannot be nested.
For example, you can mark the "CPU" of the Computer Configuration XML file with "CDATA", as shown below:
<! [CDATA [
<CPU> P4 </CPU>
]>
5. xml Annotation
To further enhance the readability of the XML file, you can add explanatory character data and expect the XML parser to not process the data. This type of information is called annotation. The annotation method in XML is exactly the same as that in HTML! -- And --> include the annotation text.
XML annotations have some syntax rules as described below:
(1) The "-" character or "--" string cannot appear in the comment text.
(2) The comment text cannot be embedded in or placed in or before the mark declaration.
(3) annotations cannot be nested.
Add comments to the Computer Configuration XML file as follows:
<! -- Describe computer configuration with XML -->
View the results in IE browser versions later than 5.0, as shown in figure <a href = 'H:/data/PIC/60090405c.jpg 'target = PIC> </a> 2:
Iii. XSL Overview
1. What is XSL?
XSL (Extensible style sheet language) is an XML style sheet. Because XML can use any tag as needed, the meaning of the tag cannot be directly parsed. In view of this, the browser cannot learn how to display an XML file. To display XML files, you must use a mechanism to describe how to display them. XSL is the preferred style table language for XML. It is not only a style table, but also a method for converting XML files, defining XML parts and patterns, and formatting XML files. The XSL language consists of the following parts:
XSLT: a language used to convert XML.
XPath: a language used to define XML parts or patterns.
2. XSL Conversion Method
XSLT is a language that converts an XML file to another type of file or XML file. XPath is a language used to address parts of XML files. Formatting is the process of converting the XSL Conversion Result into an appropriate output format. Generally, XSLT converts Each XML element to an HTML element and adds or deletes some elements to the output file.
During the conversion process, XSLT uses XPath to define the part of the source file that matches one or more predefined templates. When a match is found, XSLT converts the matching part in the source file to the result file, and the part in the source file that does not match any template remains unchanged in the result.
To understand the effect of XSL conversion, you need to create an XML file that combines with XSL. This file will be used as an example in subsequent content. The content of this file is as follows:
<? XML version = "1.0"?>
<? XML-stylesheet type = "text/XSL" href = "computer. XSL"?>
<Mycomputer>
<Computer>
<CPU> P4 </CPU>
<Ram> 256 m </Ram>
<Harddisk> 80 GB </Computer>
<Computer>
<CPU> C4 </CPU>
<Ram> 128 M </Ram>
<Harddisk> 40 Gb </Computer>
</Mycomputer>
The file contains the configurations of two computers. Therefore, according to the XML file structure described above, you need to add a unique root node "mycomputer", and finally run the file "computer. XML "is the file name to save.
In this file, "<? XML-stylesheet type = "text/XSL" href = "computer. XSL"?>" The statement is used to associate an XSL file. The content of the XSL file is as follows:
<? XML version = '000000'?>
<XSL: stylesheet xmlns: XSL = "http://www.w3.org/tr/wd-xsl">
<XSL: template match = "/">
<HTML>
<Body>
<Table border = "2">
<Tr>
<TD> CPU </TD>
<TD> Ram </TD>
<TD> harddisk </TD>
</Tr>
<XSL: For-each select = "mycomputer/computer">
<Tr>
<TD> <XSL: value-of select = "CPU"/> </TD>
<TD> <XSL: value-of select = "Ram"/> </TD>
<TD> <XSL: value-of select = "harddisk"/> </TD>
</Tr>
</XSL: For-each>
</Table>
</Body>
</Html>
</XSL: Template>
</XSL: stylesheet>
After entering the file, save it in the same folder as the "computer. XSL" file name.
Open Computer in IE browser later than version 5.0. XML file, as shown in Figure 3 (<a href = 'H:/data/PIC/60090405d.jpg 'target = PIC> figure </a>:
It can be seen that XML uses the style set by XSL to convert XML content and display it in HTML format.
3. XSL templates and elements
XSL uses one or more templates to define how to output XML elements, and uses a matching attribute to connect the template with an XML element, you can also use the matching attribute as a complete branch definition template of the XML file. The following describes the common element Syntax of XSLT.
(1) XSL: Template and XSL: Apply-templates elements:
Template is an important concept in XSL. An XSL file consists of templates. An XSL file contains at least one template. Different templates control different output formats.
The template consists of the matching mode and execution. The matching mode part defines the nodes that will be processed by the template in the XML source file, and the execution part defines the output format. The syntax of these two parts is XSL: Template and XSL: Apply-templates.
The syntax of the XSL: Template element is as follows:
<XSL: Template
Match = Pattern
Name = QNAME
Priority = Number
Mode = QNAME>
<! -- Execution content -->
</XSL: Template>
The XSL: Template element is used to define a new template. The name, priority, and mode attributes are used to distinguish different templates matching the same node. The match attribute is used to control the template matching mode, that is, to set the nodes processed by the template in the XML source file.
To match the template with the root node, enter the following statement:
<XSL: template match = "/">
<! -- File content -->
</XSL: Template>
The syntax of the XSL: Apply-templates element is as follows:
<XSL: Apply-templates
Select = node set-expression
Mode = QNAME>
</XSL: Apply-templates>
The XSL: Apply-templates element is used to set the nodes to be processed by the template. The select attribute defines the exact node name. XSL: Apply-templates is always included in the XSL: Template element.
(2) XSL: value-of element:
The syntax of the XSL: value-of element is as follows:
<XSL: value-of select = nodename/>
The XSL: value-of element is used to write the text value of the element in the source file to the output file. The nodename attribute is used to set the name of the element to be output.
(3) XSL: For-each element:
The syntax of the XSL: For-each element is as follows:
<XSL: For-each select = nodename>
<! -- Execution content -->
</XSL: For-each>
The XSL: For-each element is used to process selected nodes cyclically. The nodename attribute is used to set the name of the element to be processed cyclically.
(4) XSL: If element:
The syntax of the XSL: If element is as follows:
<XSL: If test = logical expression>
<! -- Execution content -->
</XSL: If>
XSL: The if element is similar to the IF Condition Statement in the programming language. It is used to set that the node is processed by the template only when the node meets the logical conditions.
(5) XSL: Choose, XSL: when, and XSL: otherwise elements:
Because the XSL: If element does not provide "else" Statement attributes similar to the programming language. Therefore, if you need to select multiple elements, you can use the XSL: Choose, XSL: when, and XSL: otherwise elements to implement process control.
The syntax of the XSL: Choose element is as follows:
<XSL: Choose>
<! -- Execution content -->
</XSL: Choose>
XSL: The choose element is used to select and process nodes. The execution content can contain multiple XSL: When elements and one XSL: otherwise element.
The syntax of the XSL: When element is as follows:
<XSL: When test = logical expression>
<! -- Execution content -->
</XSL: When>
XSL: The when element is used to logically select nodes. The operation is performed on nodes that match the logical expression.
The syntax of the XSL: otherwise element is as follows:
<XSL: otherwise>
<! -- Execution content -->
</XSL: otherwise>
When all the conditions listed by the XSL: When element do not match, the node is set by the XSL: otherwise element.
(6) XSL: Sort element:
The syntax of the XSL: otherwise element is as follows:
<XSL: Sort select = nodename/>
XSL: sort is used to sort XML elements. nodename indicates the name of the node to be sorted.
4. dynamically set XSL
Set XSL for the XML file, except for the static "<? XML-stylesheet type = "text/XSL" href = "XSL file name"?>" You can also set the Statement on the client and server by using the script language.
(1) set XSL on the client:
If the browser on the client supports XML, you can use XSL to convert the file to HTML and output it in the browser. More common methods can be implemented through JavaScript. On Windows, because ie5 and later versions provide XML parsing components, you can create an xmldom object to dynamically set XSL for XML. The following is its core code.
<Script language = "JavaScript">
// Create an xmldom object
VaR xmldoc = new activexobject ("Microsoft. xmldom ″);
Xmldoc. async = false;
// Load the XML file
Xmldoc. Load ("computer. xml ″);
VaR synchronized Doc = new activexobject ("Microsoft. xmldom ″);
Optional Doc. async = false;
// Load the XSL File
Using Doc. Load ("computer. XSL ″);
// Use the transformnode method to dynamically set XSL
Document. Write (xmldoc. transformnode (invalid DOC ));
</SCRIPT>
(2) Set XSL on the server:
Because not all browsers currently support XML and XSL, XML can be converted to HTML through the server. The core of the Code is similar to that of the client. The Code implemented using ASP is as follows:
<%
'Create an xmldom object
Set xmldoc = server. Createobject ("Microsoft. xmldom ″)
Xmldoc. async = false
'Load the XML file
Xmldoc. Load (server. mappath ("computer. xml ″))
Set destination Doc = server. Createobject ("Microsoft. xmldom ″)
Optional Doc. async = false
'Load the XSL File
Using Doc. Load (server. mappath ("computer. XSL ″))
'The objective of setting XSL dynamically using the transformnode Method
Response. Write (xmldoc. transformnode (invalid DOC ))
%>
Iv. Complete XML
1. xml file Constraints
XML allows you to customize tags that reflect the logical relationships between data to ensure that documents are easy to understand, clear, and easy to retrieve. Therefore, XML documents must comply with the declared rules in Document Type Definition (DTD.
DTD is used to describe the syntax and vocabulary of a markup language, that is, to define the overall structure and syntax of a document. DTD specifies all rules that the syntax analyzer needs to obtain to interpret valid XML files.
(1) DTD type:
DTD can be embedded in the leading declaration of an XML file or referenced as an external document.
Embedded DTD:
The XML file structure of the embedded DTD is as follows:
<? XML version = "1.0" encoding = "gb2312" standalone = "yes"?>
<! Doctype root element name [
Element description
]>
File Content...
External DTD:
The XML file structure using the external DTD is described as follows:
<? XML version = "1.0" encoding = "gb2312" standalone = "no"?>
<! Doctype root element name system "external DTD file name">
File Content...
The external DTD can be easily shared by multiple XML files.
(2) DTD element type declaration:
In DTD, ETD (element type declaration) is used to declare all valid elements. The syntax structure of ETD is as follows:
<! Element element name element content description>
The XML standard divides elements into four types by content:
(<A href = 'H:/data/PIC/60090405e.jpg 'target = PIC> figure </a>)
(3) DTD element attribute declaration:
Attributes can also be defined in DTD. The syntax is as follows:
<! ATTLIST element name (default value of attribute type) *>
The element name attribute is the name of the element to which the attribute belongs. The name of the property. The default attribute represents the initial value of the attribute. The following table lists the types that can be set:
(<A href = 'H:/data/PIC/60090405f.jpg 'target = PIC> figure </a>)
The property type is used to set the valid property type of the property. The valid property types are shown in the following table:
(<A href = 'H:/data/PIC/60090405g.jpg 'target = PIC> figure </a>)
2. XML Schema
(1) XML Schema Overview:
As an important part of the XML 1.0 specification, DTD can describe the structure of the XML file in detail. However, it adopts non-XML syntax rules, does not support data types, and has poor scalability. Therefore, the XML schema was created and gradually used with the DTD to better describe the XML file structure. XML schema has the following advantages:
Consistency: XML Schema uses the basic syntax rules of XML to define the file structure, so that XML can be perfectly unified, laying the foundation for the further development of XML.
Scalability: XML Schema expands the DTD and introduces data types and namespaces to improve scalability.
Interchangeable: XML Schema verifies the legitimacy of XML files and converts different XML schemas through specific ing mechanisms to achieve high-level data exchange.
Normalization: XML Schema provides a complete mechanism to restrict the use of XML tags and define the overall structure using the content and attributes of elements.
(2) XML Schema statement:
There are two types of XML Schema declaration statements:
Xmlns = "urn: Schemas-Microsoft-com: XML-Data": The statement description file is an XML schema file.
Xmlns: dt = "urn: Schemas-Microsoft-com: datatypes": This statement defines the data types that can be used in the file.
(3) XML Schema syntax:
The complete XML Schema syntax involves the following key elements:
Schema element: This is the first element in XML Schema. It is used to declare the XML file as a schema file. The schema element has two attributes: The name attribute is used to set the schema name, And the xmlns attribute is used to set the namespace contained in the schema.
Elementtype element: This element defines the elements used in the file. You can use the content attribute to declare whether an element is null, whether it contains text, whether it contains child elements, or whether it contains both text and child elements.
Attributetype element: This element defines the attribute type that appears in the file.
Group element: used to group elements in an XML file. You can use the order attribute to set the order of elements in a group or sub-group.
Datatype element: used to specify the data type for elementtype and attributetype.
Description element: Used to set description information for elementtype and attributetype.
3. xml namespace
To resolve the "Name Conflict" (that is, different entities use the same flag to describe) in a custom flag, you can assign different entities to different namespaces, the parser uses namespaces to differentiate elements, that is, XML Namespaces.
The XML namespace uses the two-segment naming method to solve the naming conflict problem, that is, the first section represents the prefix of a specific namespace, the second section is the element or attribute original name, and the two sections are separated by colons.
The XML namespace definition consists of namespace declaration, legal name definition, and application namespace scope.
(1) XML namespace declaration:
The XML namespace declaration is implemented by retaining the attribute "xmlns. The namespace Declaration includes two methods: direct and default definition:
Direct definition: xmlns: [namespace prefix] = [namespace name].
Default definition: xmlns = [namespace name].
(2) Legal name definition:
A valid name consists of a colon-separated prefix and a local part. Both the prefix and the local part must be a valid XML name.
(3) namespace scope:
The namespace scope refers to the elements and attributes that can be used by the namespace declaration. A namespace declaration can be used to describe its elements and all content of the element.
V. XML development example
1. Network Development Instance
(1) load the XML file to data island:
In HTML, you can use data islands to access XML files. The syntax for loading XML files in the data island mode on the HTML page is as follows:
<XML src = "XML file name" id = "data island name" async = "false"> </XML>
The XML file name attribute can be any XML file conforming to the syntax. The data island name attribute is the alias of the file, which will be accessed by the program. The async = "false" attribute ensures that all XML data is loaded before other HTML processing.
(2) bind the data island to an HTML table:
After the XML data is loaded, it can be displayed in an HTML table. To bind XML data to an HTML table, you only need to add the data source attribute to the table. The syntax is as follows:
<Table datasrc = "# data island name">
(3) bind the data island to the <span> or <div> element:
After binding XML data to a table, you can use the <span> or <div> element to display XML data. You only need to set the data source attribute for the <span> or <div> element on the page. The syntax is as follows:
<Span datasrc = "# data island name" dataworks = "XML mark"> </span>
<Div datasrc = "# data island name" dataworks = "corresponding XML mark"> </div>
2. Application Development Instance
XML file insertion, modification, or retrieval operations can be achieved through the XML Parser and Its provided objects. Microsoft's XML parser is provided through the MSXML. dll dynamic link library file, which is a COM object, so it can be used in any development language in windows. The following uses VB as an example.
To use the COM Object provided by MSXML. dll in VB, you must add a reference of "Microsoft XML, version 2.0" or a later version to "Reference.
The following table lists the main com interfaces provided by MSXML. dll:
(<A href = 'H:/data/PIC/60090405h.jpg 'target = PIC> figure </a>)
The following describes how to use it.
(1) Definition object:
The definition Syntax of common XML interface objects is as follows:
Dim XML as new domdocument 'create a domdocument object
Dim root as ixmldomelement 'create an ixmldomelement object
Dim node as ixmldomnode create ixmldomnode object
(2) file operations:
The common XML file operation syntax is described as follows: (use the XML interface object defined above, the same below)
Load XML file: XML. Load (XML file name)
Load XML data: XML. Load (XML data string)
Save the XML file: XML. Save (XML file name)
(3) Data Query:
You can use the domdocument object to query XML data. The operation syntax is as follows:
Query nodes with a known path: XML. selectnodes (absolute or relative path of the node)
This method returns the nodelist object. to return a single node, you can use the selectsinglenode method. If no node is found, nothing is returned.
Query nodes with known element names: Because the element names at the intermediate level are unknown, you can use the "//" symbol to represent the intermediate node and query other elements at different levels.
XML. selectnodes (Node path with "//" symbol)
Query attribute nodes: add the "@" symbol before the attribute name to return to the attribute node.
XML. selectnodes (Node path with "@" symbol)
Query text nodes: use the "text ()" keyword to obtain text nodes.
XML. selectsinglenode (Node path with the keyword "text)
Query nodes with specific conditions: Use the [] symbol to query nodes with specific conditions.
XML. selectsinglenode (node expression with the "[]" symbol)
Query nodes in multiple modes: use the "|" symbol to obtain nodes in multiple modes.
XML. selectnodes (Node path with "|" symbol)
Query any subnode: use the "*" symbol to obtain all subnodes of the current node.
XML. selectnodes (Node path with "*" symbol) |
