XML介绍与用途
- XML = Extensible Markup Language
XML与HTML的比较
XML的用途
XML的标签书写规则
合法的标签名
合理的使用属性
特殊字符与CDATA标签
有序的子元素
XML的语义约束
DTD语义约束
DTD使用规则
DTD定义节点数量
DTD引用规则
Example
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hr SYSTEM "hr.dtd">
<!-- 人力资源管理系统 -->
<hr>
<employee no="3309">
<name>张三</name>
<age>31</age>
<salary>4000</salary>
<department>
<dname>会计部</dname>
<address>XX大厦-B103</address>
</department>
</employee>
<employee no="3310">
<name>张三</name>
<age>31</age>
<salary>4000</salary>
<department>
<dname>会计部</dname>
<address>XX大厦-B103</address>
</department>
</employee>
</hr>
<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT hr (employee+)>
<!ELEMENT employee (name,age,salary,department)>
<!ATTLIST employee no CDATA "" >
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
<!ELEMENT salary (#PCDATA)>
<!ELEMENT department (dname,address)>
<!ELEMENT dname (#PCDATA)>
<!ELEMENT address (#PCDATA)>
XML Schema
Example
<?xml version="1.0" encoding="UTF-8"?>
<!-- 人力资源管理系统 -->
<hr xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="hr.xsd">
<employee no="3309">
<name>张三</name>
<age>31</age>
<salary>4000</salary>
<department>
<dname>会计部</dname>
<address>XX大厦-B103</address>
</department>
</employee>
<employee no="3310">
<name>张三</name>
<age>31</age>
<salary>4000</salary>
<department>
<dname>会计部</dname>
<address>XX大厦-B103</address>
</department>
</employee>
</hr>
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" >
<element name="hr">
<!-- complexType标签含义是复杂节点，包含子节点是必须使用这个标签 -->
<complexType>
<sequence>
<element name="employee" minOccurs="1" maxOccurs="999">
<complexType>
<sequence>
<element name="name" type="string"></element>
<element name="age" >
<simpleType>
<restriction base="integer">
<minInclusive value="18"></minInclusive>
<maxInclusive value="60"></maxInclusive>
</restriction>
</simpleType>
</element>
<element name="salary" type="integer"></element>
<element name="department">
<complexType>
<sequence>
<element name="dname" type="string"></element>
<element name="address" type="string"></element>
</sequence>
</complexType>
</element>
</sequence>
<attribute name="no" type="string" use="required"></attribute>
</complexType>
</element>
</sequence>
</complexType>
</element>
</schema>
Java解析XML
DOM文档对象模型
dom4j
dom4j读XML案例
package com.jessekkk.dom4j;
import java.util.List;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class HrReader {
public void readXml(){
String file = "d:/hr.xml";
//SAXReader类是读取XML文件的核心类，用于将XML解析后以”树“的形式保存在内存中
SAXReader reader = new SAXReader();
try {
Document document = reader.read(file);
//获取XML文档的根节点，即hr标签
Element root = document.getRootElement();
//elements方法用于获取所有指定的标签的集合
List<Element> employees = root.elements("employee");
for(Element employee : employees){
//element方法用于获取唯一的子节点对象
Element name = employee.element("name");
String empName = name.getText();//getText()用于获取标签文本
System.out.println(empName);
System.out.println(employee.elementText("age"));
System.out.println(employee.elementText("salary"));
Element department = employee.element("department");
System.out.println(department.element("dname").getText());
System.out.println(department.element("address").getText());
Attribute att = employee.attribute("no");
System.out.println(att.getText());
}
} catch (DocumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
HrReader reader = new HrReader();
reader.readXml();
}
}
dom4j写XML案例
package com.jessekkk.dom4j;
import java.io.FileOutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class HrWriter {
public void writeXml() {
String file = "d:/hr.xml";
SAXReader reader = new SAXReader();
try {
Document document = reader.read(file);
Element root = document.getRootElement();
Element employee = root.addElement("employee");
employee.addAttribute("no", "3311");
Element name = employee.addElement("name");
name.setText("李铁柱");
employee.addElement("age").setText("37");
employee.addElement("salary").setText("3600");
Element department = employee.addElement("department");
department.addElement("dname").setText("人事部");
department.addElement("address").setText("XX大厦-B105");
Writer writer = new OutputStreamWriter(new FileOutputStream(file), "UTF-8");
document.write(writer);
writer.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
HrWriter writer = new HrWriter();
writer.writeXml();
}
}
XPath路径表达式
基本表达式
谓语表达式
Jaxen介绍
Example
package com.jessekkk.dom4j;
import java.util.List;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
public class XPathTestor {
public void xpath(String xpathExp) {
String file = "d:/hr.xml";
SAXReader reader = new SAXReader();
try {
Document document = reader.read(file);
List<Node> nodes = document.selectNodes(xpathExp);
for(Node node : nodes) {
Element emp = (Element)node;
System.out.println(emp.attributeValue("no"));
System.out.println(emp.elementText("name"));
System.out.println(emp.elementText("age"));
System.out.println(emp.elementText("salary"));
System.out.println("=======================");
}
} catch (DocumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
XPathTestor testor = new XPathTestor();
// testor.xpath("/hr/employee");
// testor.xpath("//employee");
// testor.xpath("//employee[salary<4000]");
// testor.xpath("//employee[name='李铁柱']");
// testor.xpath("//employee[@no=3309]");
// testor.xpath("//employee[1]");
// testor.xpath("//employee[last()]");
// testor.xpath("//employee[position()<3]");
testor.xpath("//employee[1] | //employee[3]");
}
}
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