xml基础总结

发布时间：2020-12-16 06:06:57 所属栏目：百科来源：网络整理

导读：一 xml的定义方式： xml的定义方式有dtd和schema两种模式，这两种模式的本质区别是schema是xml模式，而dtd是文档类型定义。另外schema的可扩展性强，dtd的可扩展性较差；schema支持丰富的数据类型，dtd支持的类型有限；schema支持命名空间，dtd不支持；二

一 xml的定义方式：

xml的定义方式有dtd和schema两种模式，这两种模式的本质区别是schema是xml模式，而dtd是文档类型定义。

另外schema的可扩展性强，dtd的可扩展性较差；schema支持丰富的数据类型，dtd支持的类型有限；schema支持命名空间，dtd不支持；

二 xml的解析方式：

xml经常用到的解析方式：dom解析和sax解析；

dom解析是把xml文档看做对象，加载到内存中，如果文档较大，系统处理性能下降，适用于小文档解析，适用于随机访问；

sax解析，他是事件驱动的，解析时候不需要加载整个文档，在解析遇到文档开始和结束，标签的开始和结束时候，会触发事件，对事件使用回调函数来解析，适用于文档的顺序解析。

三两种解析方式解析实例

(a) dom解析：

1 随机访问xml:

student.xml

<?xml version="1.0" encoding="GB2312" standalone="no"?>
<students>
<student name="张三">	
	<age>20</age>
	<school>北方交大</school>
</student>
<student name="李四">	
	<age>21</age>
	<school>北大</school>
</student>
<student name="王五">	
	<age>18</age>
	<school>清华</school>
</student>
</students>

XMLTools.java

package com.jx;

import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class XMLTools {

	public static void main(String[] args) {
		List names=new ArrayList();
		List ages=new ArrayList();
		List schools=new ArrayList();
		
		try {
			DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
			DocumentBuilder db=dbf.newDocumentBuilder();
			Document d=db.parse("src/student.xml");
			
			NodeList nodeList=d.getElementsByTagName("student");
			for(int i=0;i<nodeList.getLength();i++){
				Node node=nodeList.item(i);
				Element element=(Element)node;
				names.add(element.getAttribute("name"));	
				
			}
			
			NodeList nodeList1=d.getElementsByTagName("age");			
			for(int i=0;i<nodeList1.getLength();i++){
				Node node=nodeList1.item(i);
				Element element=(Element)node;
				ages.add(element.getFirstChild().getNodeValue());
				
			}
			
			NodeList nodeList2=d.getElementsByTagName("school");	
			for(int i=0;i<nodeList2.getLength();i++){
				Node node=nodeList2.item(i);
				Element element=(Element)node;
				schools.add(element.getFirstChild().getNodeValue());
				
			}
			
			for(int i=0;i<names.size();i++){
				System.out.println((String)names.get(i)+"-"+(String)ages.get(i)+"-"+(String)schools.get(i));
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

2 增加元素

package com.jx;

import java.io.FileOutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

public class Add {

	public static void main(String[] args) {
		try {
			DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
			DocumentBuilder db=dbf.newDocumentBuilder();
			Document d=db.parse("src/student.xml");
			
			Element studentElement=d.createElement("student");
			studentElement.setAttribute("name","赵六");
			Element ageElement=d.createElement("age");
			Text ageText=d.createTextNode("22");
			Element schoolElement=d.createElement("school");
			Text schoolText=d.createTextNode("北京理工大学");
			
			ageElement.appendChild(ageText);
			schoolElement.appendChild(schoolText);
			studentElement.appendChild(ageElement);
			studentElement.appendChild(schoolElement);
			
			NodeList nodeList=d.getElementsByTagName("students");
			Element students=(Element) nodeList.item(0);
			students.appendChild(studentElement);
			System.out.println("添加成功");
			
			//保持XML文件
			TransformerFactory transformerFactory = TransformerFactory.newInstance();
			Transformer transformer = transformerFactory.newTransformer();
			DOMSource domSource = new DOMSource(d);
			//设置编码类型
			transformer.setOutputProperty(OutputKeys.ENCODING,"gb2312");
			StreamResult result = new StreamResult(new FileOutputStream("src/student.xml"));
			//把DOM树转换为XML文件
			transformer.transform(domSource,result);
			
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

3 修改元素

package com.jx;

import java.io.FileOutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class Update {

	public static void main(String[] args) {
		try {
			DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
			DocumentBuilder db=dbf.newDocumentBuilder();
			Document d=db.parse("src/student.xml");
			//找到要修改的节点
			NodeList nodeList=d.getElementsByTagName("student");

			for(int i=0;i<nodeList.getLength();i++){
				Element studentElement=(Element) nodeList.item(i);
				if(studentElement.getAttribute("name").equalsIgnoreCase("赵六")){
					studentElement.setAttribute("name","甲");
					
					Node ageNode=studentElement.getFirstChild();
					Element ageElement=(Element) ageNode;
					ageNode.getFirstChild().setNodeValue("20");
					
					Node schoolNode=studentElement.getLastChild();
					Element schoolElement=(Element) schoolNode;
					schoolElement.getFirstChild().setNodeValue("北航");
					System.out.println("修改完毕");
				}
				
			}
			
			
			//保持XML文件
			TransformerFactory transformerFactory = TransformerFactory.newInstance();
			Transformer transformer = transformerFactory.newTransformer();
			DOMSource domSource = new DOMSource(d);
			//设置编码类型
			transformer.setOutputProperty(OutputKeys.ENCODING,result);
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

4 删除元素

package com.jx;

import java.io.FileOutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class Delete {

	public static void main(String[] args) {
		try {
			DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
			DocumentBuilder db=dbf.newDocumentBuilder();
			Document d=db.parse("src/student.xml");
			
			NodeList nodeList=d.getElementsByTagName("student");
			for(int i=0;i<nodeList.getLength();i++){
				Element element=(Element)nodeList.item(i);
				if(element.getAttribute("name").equalsIgnoreCase("甲")){
					d.getElementsByTagName("students").item(0).removeChild(nodeList.item(i));
					System.out.println("移除成功");
				}
			}
			
			//保持XML文件
			TransformerFactory transformerFactory = TransformerFactory.newInstance();
			Transformer transformer = transformerFactory.newTransformer();
			DOMSource domSource = new DOMSource(d);
			//设置编码类型
			transformer.setOutputProperty(OutputKeys.ENCODING,result);
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

(b)sax解析

1 解析含有文本节点的xml

emp.xml;

<?xml version="1.0" encoding="GB2312" standalone="no"?><emps>
<emp>	
	<name>张三</name>
	<age>22</age>
</emp>
<emp>	
	<name>李四</name>
	<age>20</age>
</emp>
</emps>

Emp.java

package com.sax;

public class Emp {
	private String name;
	private String age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	
}

SaxXML.java

package com.sax;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class SaxXML extends DefaultHandler{
	private Emp emp;
	private List<Emp> emps;
	private String preTag;//记录解析时候的上一个节点名称

    public void startDocument() throws SAXException {
	   emps=new ArrayList<Emp>();      
    }
    
    public void startElement(String uri,String localName,String name,Attributes attr) throws SAXException {
        if ("emp".equals(name)) {
        	emp = new Emp();
        }        
        preTag = name;//将正在解析的节点名称赋给preTag 

    }
    
    public void endElement(String uri,String name)
            throws SAXException {
        if ("emp".equals(name)) {
            emps.add(emp);
        }        
        preTag = null;
    }
    
    public void characters(char[] ch,int start,int length)
            throws SAXException {
        if (preTag != null) {
            String data = new String(ch,start,length);
            if ("name".equals(preTag)) {
               emp.setName(data);
            }
            if ("age".equals(preTag)) {
               emp.setAge(data);
            }
          
        }
    }
    
    public List<Emp> getEmps(InputStream xmlStream) throws Exception{  
        SAXParserFactory factory = SAXParserFactory.newInstance();  
        SAXParser parser = factory.newSAXParser();  
        SaxXML handler = new SaxXML();  
        parser.parse(xmlStream,handler);  
        return handler.getEmps();  
    }  
      
   public List<Emp> getEmps(){  
        return emps;  
   }

   public static void main(String[] args) throws Exception {
	   SaxXML saxXML=new SaxXML();
	   InputStream inputStream=saxXML.getClass().getClassLoader().getResourceAsStream("emp.xml");
	   List<Emp> empList=saxXML.getEmps(inputStream);
	   for(Emp e:empList){
		   System.out.println(e.getName()+":"+e.getAge());
	   }
   }
}

2 解析含有属性节点的xml

teacher.xml

<?xml version="1.0" encoding="GB2312" standalone="no"?><teachers>
<teacher>
	<name data="李老师"/>
	<gender data="男"/>
</teacher>
<teacher>
	<name data="张老师"/>
	<gender data="女"/>
</teacher>
<teacher>
	<name data="刘老师"/>
	<gender data="女"/>
</teacher>
</teachers>

Teacher.java

package com.sax;

public class Teacher {
	private String name;
	private String gender;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getGender() {
		return gender;
	}
	public void setGender(String gender) {
		this.gender = gender;
	}
	
}

SaxXmlTeacher.java

package com.sax;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class SaxXmlTeacher extends DefaultHandler{
	private Teacher teacher;
	private List<Teacher> teachers;
	private String preTag;//记录解析时候的上一个节点名称
	
	
	 public void startDocument() throws SAXException {
		 teachers=new ArrayList<Teacher>();   
		 
	 }
	 
    public void startElement(String uri,Attributes attr) throws SAXException {
        if ("teacher".equals(name)) { 
        	teacher=new Teacher();
        	 preTag = name;//将正在解析的节点名称赋给preTag 
        	
        }        
        if ("name".equals(name)) {
        	teacher.setName(attr.getValue("data"));        	
         }
        if ("gender".equals(name)) {
        	teacher.setGender(attr.getValue("data"));
        }

    }
	 
    public void endElement(String uri,String name)
            throws SAXException {
        if ("teacher".equals(name)) {
        	teachers.add(teacher);
        	 preTag = null;
        }        
       
    }
    public void characters(char[] ch,int length)
            throws SAXException {

    }
    public List<Teacher> getTeachers(InputStream xmlStream) throws Exception{  
        SAXParserFactory factory = SAXParserFactory.newInstance();  
        SAXParser parser = factory.newSAXParser();  
        SaxXmlTeacher handler = new SaxXmlTeacher();  
        parser.parse(xmlStream,handler);  
        return handler.getTeachers();  
    }  
      
   public List<Teacher> getTeachers(){  
        return teachers;  
   }
   public static void main(String[] args) throws Exception {
	   SaxXmlTeacher saxXML=new SaxXmlTeacher();
	   InputStream inputStream=saxXML.getClass().getClassLoader().getResourceAsStream("teacher.xml");
	   List<Teacher> teachers=saxXML.getTeachers(inputStream);
	   for(Teacher e:teachers){
		   System.out.println(e.getName()+":"+e.getGender());
	   }
	
   }
}

3 解析既含有属性节点又含有文本节点的xml

student.xml

<?xml version="1.0" encoding="GB2312" standalone="no"?><students>
<student name="张三">	
	<age>20</age>
	<school>北方交大</school>
</student>
<student name="李四">	
	<age>21</age>
	<school>北大</school>
</student>
<student name="王五">	
	<age>18</age>
	<school>清华</school>
</student>
</students>

Student.java

package com.sax;

public class Student {
	private String name;
	private String age;
	private String school;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	public String getSchool() {
		return school;
	}
	public void setSchool(String school) {
		this.school = school;
	}
	
}

SaxXmlStudent.java

package com.sax;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class SaxXmlStudent extends DefaultHandler{
	private Student student;
	private List<Student> students;
	private String preTag;//记录解析时候的上一个节点名称
	
	 public void startDocument() throws SAXException {
		 students=new ArrayList<Student>();  
		 
	 }
	 
	 public void startElement(String uri,Attributes attr) throws SAXException {
	        if ("student".equals(name)) { 
	        	student=new Student();
	        	
	        	
	        }   
	        
	        preTag = name;//将正在解析的节点名称赋给preTag 
	        
	        if ("student".equals(name)) {
	        	student.setName(attr.getValue("name"));        	
	         }	       

	    }
	 
	 public void characters(char[] ch,int length)
	            throws SAXException {
	        if (preTag != null) {
	            String data = new String(ch,length);
	            if ("school".equals(preTag)) {
	            	student.setSchool(data);
	            }
	            if ("age".equals(preTag)) {
	               student.setAge(data);
	            }
	          
	        }
	    }
	 
	 public void endElement(String uri,String name)
	            throws SAXException {
	        if ("student".equals(name)) {
	        	students.add(student);
	        }        
	        preTag = null;
	    }
	 
	 public List<Student> getStudents(InputStream xmlStream) throws Exception{  
		 SAXParserFactory factory = SAXParserFactory.newInstance();  
	        SAXParser parser = factory.newSAXParser();  
	        SaxXmlStudent handler = new SaxXmlStudent();  	      
	        parser.parse(xmlStream,handler);  
	        return handler.getStudents();  
	    }  
	      
	   public List<Student> getStudents(){  
	        return students;  
	   }
	   
	   public static void main(String[] args) throws Exception {
		   SaxXmlStudent saxXML=new SaxXmlStudent();
		   InputStream inputStream=saxXML.getClass().getClassLoader().getResourceAsStream("student.xml");
		   List<Student> students=saxXML.getStudents(inputStream);
		   for(Student e:students){
			   System.out.println(e.getName()+"-"+e.getAge()+"-"+e.getSchool());
		   }
		
	   }
}

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!