java 01 XML

SAX 解析方式 相比DOM 快 更有效 不能对节点修改

DOM解析方法 慢 内存有压力，但是可以遍历和修改节点

 

 

使用DOM 解析XML的流程

1、创建SAXReader 

2、用SAXReader 读取XML文档并返回Document对象

DOM解析耗时耗资源的体现

DOM会将XML文档全部读取并以一个Document对象形式存于内存

Document对象用于描述解析的XML文档

3、根据Document对象获取根元素

 Element的每一个实例用于表示xml文档中的一个元素  一堆标签 

4、按照xml的结构从根元素中开始逐级获取子元素以达到遍历xml的目的

 

 

 

 

String  getName()

获取当前标签的名字

 

List elements()

获取当前标签下的所有子标签

 

List elements(String name)

获取当前变迁下所有同名子标签

 

　　　　　　　SAXReader xmlRead = new SAXReader();
            Document doc = xmlRead.read(new FileInputStream("emplist.xml"));
            Element root = doc.getRootElement();
            List<Emp> empList = new ArrayList<Emp>();
            List<Element> elements = root.elements();
            
            for(Element sub:elements) {
                int id = Integer.parseInt(sub.attribute("id").getValue());
                Element nameEle = sub.element("name");
                String name = nameEle.getTextTrim();
                int age = Integer.parseInt(sub.element("age").getTextTrim());
                String gender  = sub.element("gender").getTextTrim();
                int salary = Integer.parseInt(sub.element("salary").getTextTrim());
                empList.add(new Emp(id,name,age,gender,salary));
            }
            System.out.println(empList.size());
            for(Emp sub:empList) {
                System.out.println(sub.toString());
            }

 

 

写出XML文档的大致步骤

创建应给Document 对象 表示一个空白的xml文档

想Document对象中添加根元素

按照应当生成的xml文档的格式逐级向根元素中添加子元素以形成xml文档格式

创建XmlWriter

通过XmlWriter将Document 写出

 

Document doc = DocumentHelper.createDocument();

通过DocumentHepler  创建一个Document 对象 简单

doc.addElement("xx")

doc对象只能调用一次addElement 添加根元素  返回一个Element对象

Element emp = root.addElement("emp");

emp 对象可以可以调用addElement 添加子元素  返回一个Element对象 

emp.addAttribute("id", String.valueOf(sub.getId()));

emp 添加属性 返回自身 

emp.addText(arg0)

emp 添加文本.返回自身 

package maven;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.SAXWriter;
import org.dom4j.io.XMLWriter;

public class WriteXml {
    public static void main(String[] args) {
        List<Emp> empList = new ArrayList<Emp>();
        empList.add(new Emp(1,"长大",22,"女",1000));
        empList.add(new Emp(3,"长二",20,"男",2000));
        empList.add(new Emp(5,"长三",18,"女",1000));
        empList.add(new Emp(7,"长四",16,"男",2000));
        empList.add(new Emp(9,"长五",14,"女",3000));
        
        Document doc = DocumentHelper.createDocument();
        Element root = doc.addElement("list");
        for(Emp sub : empList) {
            Element emp = root.addElement("emp");
            emp.addAttribute("id", String.valueOf(sub.getId()));
            emp.addElement("name").addText(sub.getName());
            emp.addElement("age").addText(String.valueOf(sub.getAge()));
            emp.addElement("gender").addText(sub.getGender());
            emp.addElement("salary").addText(String.valueOf(sub.getSalary()));
        }
        FileOutputStream fos = null;
        XMLWriter weriter = null;
        try {
            fos = new FileOutputStream("emplist2.xml");
            weriter  = new  XMLWriter();
            weriter.setOutputStream(fos);
            weriter.write(doc);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(weriter != null) {
                try {
                    weriter.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

 

Xpath

/ 斜杠 分隔符

.当前

..上一层

/ 根节点

//任意位置的节点

@ 某个属性

条件

[]

 

 

<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.1.4</version>
</dependency>

 

 

package maven;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;

public class ReadXml2 {
    public static void main(String[] args) {
        try {
            SAXReader read  = new SAXReader();
            Document doc = read.read(new FileInputStream("emplist2.xml"));
            List list = doc.selectNodes("//*");
            System.out.print(list.size());
            
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (DocumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
}