java学习之xml

xml的处理有两种方式dom和Sax

其中dom有3套api ，分别是dom和jdom和dom4j 

package com.gh.xml;

import java.io.File;
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.Node;
import org.w3c.dom.NodeList;
/**
 * Dom模式读取xml
 * @author ganhang
 *
 */
public class DomDemo {
    public static void main(String[] args) throws Exception {
        // 创建dom解析器工厂
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        // 创建一个dom解析器
        DocumentBuilder db = dbf.newDocumentBuilder();
        // 关联文件
        File f = new File("src/1.xml");
        // 开始解析
        Document doc = db.parse(f);// 传文件或者字节流
        // 根据节点获取数据
        NodeList nl = doc.getElementsByTagName("teacher");
        List<Teacher> teachers = new ArrayList<Teacher>();
        Teacher t = null;
        for (int i = 0; i < nl.getLength(); i++) {
            Node teacherNode = nl.item(i);// 获取每个teacher节点
            // 得到节点的属性id的值
            String str = teacherNode.getAttributes().getNamedItem("id")
                    .getNodeValue();
            //System.out.println(str);
            t = new Teacher();
            t.setId(Integer.parseInt(str));
            // 获取teacher节点下的所有子节点
            NodeList childNodeList = teacherNode.getChildNodes();
            //System.out.println(childNodeList.getLength());
            for (int j = 0; j < childNodeList.getLength(); j++) {
                // 注意teacher有三个子节点#text name #text
                Node childNode = childNodeList.item(j);
                //System.out.println(childNode.getNodeName());
                // 取name的子节点的值
                if ("name".equals(childNode.getNodeName())) {
                    t.setName(childNode.getFirstChild().getNodeValue());
                }
            }
            teachers.add(t);
        }
        System.out.println(teachers);
    }
}

package com.gh.xml;

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

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;

public class JdomDemo {
    public static void main(String[] args) throws Exception {
        SAXBuilder sb = new SAXBuilder();// 创建jdom解析器
        InputStream in = Thread.currentThread().getContextClassLoader()
                .getResourceAsStream("1.xml");
        Document doc = sb.build(in);
        //拿根元素
        Element roote = doc.getRootElement();
        //根据根元素拿子元素
        List<Element> liste = roote.getChildren();
        List<Teacher> teachers=new ArrayList<Teacher>();
        Teacher t=null;//注意必须要在里面new，不然teachers添加的都是重复的t；
        //遍历子元素,也可以返回一个iterator遍历；
        for (int i = 0; i < liste.size(); i++) {
            t=new Teacher();
            Element e = liste.get(i);
            t.setId(Integer.parseInt(e.getAttributeValue("id")));
            t.setName(e.getChildText("name"));
            teachers.add(t);
        }
        System.out.println(teachers);
    }
}

package com.gh.xml;

import java.io.File;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
/**
 * Dom4j 性能最好
 * @author ganhang
 *
 */
public class Dom4jDemo {
    public static void main(String[] args) throws Exception {
        SAXReader sr=new SAXReader();
        File f=new File("src/1.xml");
        Document doc=sr.read(f);
        Element roote=doc.getRootElement();
        Iterator<Element> iters=roote.elementIterator();
        Teacher t=null;
        List<Teacher> list=new ArrayList<Teacher>();
        while(iters.hasNext()){
            t=new Teacher(); 
            Element e=iters.next();
            t.setId(Integer.parseInt(e.attributeValue("id")));
            t.setName(e.elementText("name"));
            list.add(t);
        }
        System.out.println(list);
    }
}

package com.gh.xml;

import java.io.InputStream;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
/**
 * SAX读xml
 * @author ganhang
 *
 */
public class SaxDemo {
    public static void main(String[] args) throws Exception {
        //创建SAX解析器工厂
        SAXParserFactory spf = SAXParserFactory.newInstance();
        //创建sax解析器
        SAXParser sp = spf.newSAXParser();
        //用字符流读xml
        InputStream is = Thread.currentThread().getContextClassLoader()
                .getResourceAsStream("1.xml");
        MyHandler dh=new MyHandler();//实例化引擎
        //开始解析
        sp.parse(is, dh);
        System.out.println(dh.getList());
        
    }
}

package com.gh.xml;

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

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
/**
 * Sax模式的事件处理引擎
 * @author ganhang
 *
 */
public class MyHandler extends DefaultHandler {
    private List<Teacher> list = null;
    private Teacher t = null;
    private String flag = null;
    //开始读入文件
    @Override
    public void startDocument() throws SAXException {
        list=new ArrayList<Teacher>();
    }
    //开始读元素
    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes attributes) throws SAXException {
        flag = qName;
        if ("teacher".equals(qName)) {
            t=new Teacher();//注意要在这new一个新的Teacher不然list添加会重复
            t.setId(Integer.parseInt(attributes.getValue("id")));
            //System.out.println(t.getId());
        }
    }
    //读字符数据
    @Override
    public void characters(char[] ch, int start, int length)
            throws SAXException {
        if ("name".equals(flag)) {
            t.setName(new String(ch, start, length));
             //System.out.println(t.getName());
        }
    }
    //结束元素时干嘛
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        if ("teacher".equals(qName)) {
            list.add(t);
            //System.out.println(list.get(0));
        }//System.out.println(t);
            flag = null;
    }
    //结束文件时干嘛
    @Override
    public void endDocument() throws SAXException {
        System.out.println("解析成功！");
        //System.out.println(list.get(0));
    }
    public List<Teacher> getList() {
        return list;
    }

}

package com.gh.xml;

public class Teacher {
    private int id;
    private String name;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public Teacher(int id, String name) {
        this.id = id;
        this.name = name;
    }
    public Teacher() {
        super();
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Teacher [id=" + id + ", name=" + name + "]";
    }
}

package com.gh.xml;

import java.beans.XMLDecoder;
import java.beans.XMLEncoder;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
/**
 * xml和对象之间的转换
 * @author ganhang
 *
 */
public class ObjectAndXmlDemo {
    /**
     * 把对象转成xml
     * @param obj
     * @param file
     * @throws Exception 
     */
    public static void object2xml(Teacher obj,File file) throws Exception{
        BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(file));
        XMLEncoder encode=new XMLEncoder(bos);
        encode.writeObject(obj);
        encode.flush();
        encode.close();
        bos.close();
        System.out.println("写入成功");
    }
    /**
     * xml转成对象
     * @param file
     * @return
     * @throws Exception
     */
    public static Teacher xml2object(File file) throws Exception{
        BufferedInputStream bis=new BufferedInputStream(new FileInputStream(file));
        XMLDecoder decode =new XMLDecoder(bis);
        Teacher t=(Teacher)decode.readObject();
        decode.close();
        bis.close();
        System.out.println("读入成功");
        return t;
    }
    public static void main(String[] args) throws Exception {
        //Teacher t=new Teacher(1,"小白");
        //object2xml(t,new File("src/2.xml"));
        System.out.println(xml2object(new File("src/2.xml")));
    }
}

1.xml

<?xml version="1.0" encoding="UTF-8"?>
<person>
    <teacher id="1">
        <name>小白</name>
        <desc>hehe1</desc>
    </teacher>
    
    <teacher id="2">
        <name>小黑</name>
        <desc>hehe2</desc>
    </teacher>
    <teacher id="3">
        <name>小红</name>
        <desc>hehe3</desc>
    </teacher>
</person>

2.xml

<?xml version="1.0" encoding="UTF-8"?>
<java version="1.7.0_79" class="java.beans.XMLDecoder">
 <object class="com.gh.xml.Teacher">
  <void property="id">
   <int>1</int>
  </void>
  <void property="name">
   <string>小白</string>
  </void>
 </object>
</java>