JAXP进行DOM和SAX解析

1.常用XML的解析方式：DOM和SAX

1）DOM思想：将整个XML加载内存中，形成文档对象，所以对XML操作都对内存中文档对象进行。

2）SAX思想：一边解析，一边处理，一边释放内存资源---不允许在内存中保留大规模XML数据

3）DOM和SAX的区别

DOM：支持回写，会将整个XML载入内存，以树形结构方式存储

            XML比较复杂的时候，或者当你需要随机处理文档中数据的时候不建议使用

SAX：相比DOM是一种更为轻量级的方案

          无法在读取过程中修改XML数据

2.常用解析开发包：JAXP、DOM4J

3.DOM解析原理图

4.使用JAXP进行DOM解析

JAXP:(Java API for XML Processing)开发包是JavaSE的一部分，它由以下几个包及其子包组成：

org.w3c.dom:提供DOM方式解析XML的标准接口

org.xml.sax:提供SAX方式解析XML的标准接口

javax.xml:提供了解析XML文档的类

5.JAXP进行DOM解析的实例（增删改查）

book.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?><书架><书 ISBN="a11" 出版社="清华大学出版社"><书名>JavaSE基础</书名><作者>张三</作者><批发价>35.00元</批发价><售价>38.00元</售价></书><书 ISBN="b11" 出版社="北京大学出版社"><书名>Android</书名><作者>李四</作者><售价>38.00元</售价></书>
</书架>

JaxpDomDemo.java

package cn.lsl.jaxp;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
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 JaxpDomDemo {public static void main(String[] args) throws Exception {//得到解析工厂DocumentBuilderFactoryDocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();//得到解析器DocumentBuilderDocumentBuilder builder =  factory.newDocumentBuilder();//解析指定的XML文档，得到代表内存DOM树的Document对象Document document = builder.parse("src/book.xml");test8(document);}//1.得到某个具体节点内容：打印第2本书的作者public static void test1(Document document){//根据标签的名称获取所有的作者元素NodeList nodeList = document.getElementsByTagName("作者");//按照索引取第2个作者元素Node node = nodeList.item(1);//打印该元素的文本String text = node.getTextContent();System.out.println(text);}// 2、遍历所有元素节点:打印元素的名称public static void test2(Node node){//判断当前节点是不是一个元素节点if(node.getNodeType() == Node.ELEMENT_NODE){//如果是：打印他的名称
            System.out.println(node.getNodeName());}//查找子节点NodeList nodeList = node.getChildNodes();int len = nodeList.getLength();for (int i = 0; i < len; i++) {Node n = nodeList.item(i);test2(n);}}//3、修改某个元素节点的主体内容:把第一本书的售价改为38.00元public static void test3(Document document) throws Exception{//找到第一本书的售价NodeList nodeList = document.getElementsByTagName("售价");//设置其主体内容Node node = nodeList.item(0);node.setTextContent("38.00元");//把内存中Document树写回xml文件中TransformerFactory factory = TransformerFactory.newInstance();Transformer ts = factory.newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/book.xml"));}//4.向指定元素节点中增加子元素节点:第一本中增加子元素<内部价>29.00</内部价>public static void test4(Document document) throws Exception{//创建一个新的元素并设置其主体内容Element e = document.createElement("内部价");e.setTextContent("29.00元");//找到第一本书元素Node firstBookNode = document.getElementsByTagName("书").item(0);//把新节点挂接到第一本书上
        firstBookNode.appendChild(e);//把内存中Document树写回XML文件中TransformerFactory factory = TransformerFactory.newInstance();Transformer ts = factory.newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/book.xml"));}//5.向指定元素节点上增加同级元素节点:在第一本书的售价前面增加批发价public static void test5(Document document) throws Exception{//创建一个新的元素并设置其中的主题内容Element e = document.createElement("批发价");e.setTextContent("35.00元");//找到第一本书的售价Node firstPrice = document.getElementsByTagName("售价").item(0);//在售价的前面加入新建的元素：增加子元素一定要用父元素来增加
        firstPrice.getParentNode().insertBefore(e, firstPrice);//把内存中Document树写回XML文件中TransformerFactory factory = TransformerFactory.newInstance();Transformer ts = factory.newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/book.xml"));}//6.删除指定元素节点：删除内部价public static void test6(Document document) throws Exception{//找到内部价节点，用父节点删除Node n = document.getElementsByTagName("内部价").item(0);n.getParentNode().removeChild(n);//把内存中Document书写回XML文件中TransformerFactory factory = TransformerFactory.newInstance();Transformer ts = factory.newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/book.xml"));}//7、操作XML文件属性:打印第一本书的出版社public static void test7(Document document){//得到第一本书Node n = document.getElementsByTagName("书").item(0);//打印指定属性的取值Element e = (Element)n;System.out.println(e.getAttribute("出版社"));}//8、添加一个出版社属性给第二本书public static void test8(Document document) throws Exception{//得到第二本书Node n = document.getElementsByTagName("书").item(1);//打印指定属性的取值Element e = (Element)n;e.setAttribute("出版社", "北京大学出版社");//把内存中Document树写回XML文件中TransformerFactory factory  = TransformerFactory.newInstance();Transformer ts = factory.newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/book.xml"));}    
}

6.案例（学生成绩的增删改查，采用分层开发）

案例原型

exam.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?><exam><student examid="444" idcard="333"><name>李四</name><location>大连</location><grade>97</grade></student><student examid="666" idcard="555"><name>小舒</name><location>福建</location><grade>90.0</grade></student>
</exam>

实体类：Student.java

package cn.lsl.domain;public class Student {private String idcard;private String examid;private String name;private String location;private Double grade;public String getIdcard() {return idcard;}public void setIdcard(String idcard) {this.idcard = idcard;}public String getExamid() {return examid;}public void setExamid(String examid) {this.examid = examid;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getLocation() {return location;}public void setLocation(String location) {this.location = location;}public Double getGrade() {return grade;}public void setGrade(Double grade) {this.grade = grade;}@Overridepublic String toString() {return "Student [examid=" + examid + ", grade=" + grade + ", idcard="+ idcard + ", location=" + location + ", name=" + name + "]";}
}

工具类：DocumentUtil.java

package cn.lsl.util;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
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;
//操作XML的工具类
//工具类中的异常可以抛也可以处理
public class DocumentUtil {public static Document getDocument() throws Exception{DocumentBuilder builder =  DocumentBuilderFactory.newInstance().newDocumentBuilder();return builder.parse("src/exam.xml");}public static void write2xml(Document document) throws Exception{Transformer ts = TransformerFactory.newInstance().newTransformer();ts.transform(new DOMSource(document), new StreamResult("src/exam.xml"));}
}

DAO层：（StudentDao.java）

package cn.lsl.dao;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import cn.lsl.domain.Student;
import cn.lsl.util.DocumentUtil;public class StudentDao {//添加学生信息到XML中public boolean createStudent(Student s){boolean result = false;try{Document document = DocumentUtil.getDocument();//创建name、location、grade元素并设置内容Element nameE = document.createElement("name");nameE.setTextContent(s.getName());Element locationE = document.createElement("location");locationE.setTextContent(s.getLocation());Element gradeE = document.createElement("grade");gradeE.setTextContent(s.getGrade()+"");//创建student元素，并设置属性Element studentE = document.createElement("student");studentE.setAttribute("idcard", s.getIdcard());studentE.setAttribute("examid", s.getExamid());studentE.appendChild(nameE);studentE.appendChild(locationE);studentE.appendChild(gradeE);//得到exam元素，把student挂接上去Node node = document.getElementsByTagName("exam").item(0);node.appendChild(studentE);//写回XML文件中
            DocumentUtil.write2xml(document);result = true;}catch(Exception e){throw new RuntimeException(e);    //异常转义。异常链
        }return result;}//根据准考证号查询学生信息public Student findStudent(String examid){Student s = null;try{Document document = DocumentUtil.getDocument();//得到所有student元素NodeList nodelist = document.getElementsByTagName("student");//遍历student元素，判断他的examid属性的取值是否与参数匹配for (int i = 0; i < nodelist.getLength(); i++) {Node node = nodelist.item(i);if(node instanceof Element){Element e = (Element)node;if(e.getAttribute("examid").equals(examid)){//如果匹配，说明找到了学生，创建学生对象s = new Student();s.setExamid(examid);s.setIdcard(e.getAttribute("idcard"));s.setName(e.getElementsByTagName("name").item(0).getTextContent());s.setLocation(e.getElementsByTagName("location").item(0).getTextContent());s.setGrade(Double.parseDouble(e.getElementsByTagName("grade").item(0).getTextContent()));}}}}catch(Exception e){throw new RuntimeException(e);}return s;}//根据学生姓名删除学生public boolean deleteStudent(String name){boolean result = false;try{//得到Document对象Document document = DocumentUtil.getDocument();NodeList nodelist = document.getElementsByTagName("name");for(int i=0; i<nodelist.getLength(); i++){Node node = nodelist.item(i);if(node.getTextContent().equals(name)){node.getParentNode().getParentNode().removeChild(node.getParentNode());//写回XML文档
                    DocumentUtil.write2xml(document);result = true;break;}}}catch(Exception e){throw new RuntimeException(e);}return result;}
}

View层（Main.java）

package cn.lsl.view;import java.io.BufferedReader;
import java.io.InputStreamReader;import cn.lsl.dao.StudentDao;
import cn.lsl.domain.Student;public class Main {public static void main(String[] args) {try{StudentDao dao = new StudentDao();System.out.println("a、添加学生\tb、删除学生\tc、查询成绩");System.out.println("请输入操作类型");BufferedReader br = new BufferedReader(new InputStreamReader(System.in));String operation = br.readLine();if("a".equals(operation)){//添加操作System.out.println("请输入学生姓名");String name = br.readLine();System.out.println("请输入学生准考证号");String examid = br.readLine();System.out.println("请输入学生身份证号");String idcard = br.readLine();System.out.println("请输入学生所在地");String location = br.readLine();System.out.println("请输入学生成绩");String grade = br.readLine();Student s = new Student();s.setExamid(examid);s.setIdcard(idcard);s.setName(name);s.setLocation(location);s.setGrade(Double.parseDouble(grade));//System.out.println(s);boolean b = dao.createStudent(s);if(b){System.out.println("---添加成功---");}else{System.out.println("对不起！数据有误");}}else if("b".equals(operation)){System.out.println("请输入要删除的学生姓名:");String name = br.readLine();boolean b = dao.deleteStudent(name);if(b){System.out.println("--删除成功--");}else{System.out.println("对不起！删除失败或者学生不存在");}}else if("c".equals(operation)){//查询操作System.out.println("请输入要查询的学生准考证号:");String examid = br.readLine();Student s = dao.findStudent(examid);if(s == null){System.out.println("对不起！您查询的学生不存在");}else{System.out.println(s);}}else{System.out.println("请输入正确的操作类型");}}catch(Exception e){System.out.println("对不起！服务器忙！");}}
}

7.SAX解析原理图

 

8. SAX采用事件处理的方式解析XML文件，利用 SAX 解析 XML 文档，涉及两个部分：解析器和事件处理器。

9.SAX解析

实例一：

book.xml

<?xml version="1.0" encoding="UTF-8"?>
<书架> <书 出版社="清华大学出版社"> <书名>JavaSE基础</书名>  <作者>张三</作者>  <售价>38.00</售价>  <内部价>19.00</内部价> </书>  <书> <书名>Android</书名>  <作者>李四</作者>  <售价>28.00</售价> </书> 
</书架>

SAXDemo1.java

package cn.lsl.sax;import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;//JAXP进行SAX解析
public class SAXDemo1 {public static void main(String[] args) throws Exception {//得到解析工厂SAXParserFactorySAXParserFactory factory = SAXParserFactory.newInstance();//得到解析器SAXParserSAXParser parser = factory.newSAXParser();//得到XML读取器：XMLReaderXMLReader reader = parser.getXMLReader();//注册内容处理器：ContentHandlerreader.setContentHandler(new MyContentHandler());//取出XML文档reader.parse("src/book.xml");}
}class MyContentHandler implements ContentHandler{//解析到文档开始时被调用
    @Overridepublic void startDocument() throws SAXException {System.out.println("解析到了文档的开始");}//解析到了元素开始时被调用：    qName元素名称
    @Overridepublic void startElement(String uri, String localName, String qName,Attributes atts) throws SAXException {System.out.println("解析到了元素的开始："+qName);}//解析到了文本内容被调用
    @Overridepublic void characters(char[] ch, int start, int length)throws SAXException {System.out.println("文本内容："+new String(ch,start,length));}//解析到元素结束时被调用
    @Overridepublic void endElement(String uri, String localName, String qName)throws SAXException {System.out.println("解析到了元素的结束："+qName);}//解析到文档结束时被调用
    @Overridepublic void endDocument() throws SAXException {System.out.println("解析到了文档的结束");}@Overridepublic void endPrefixMapping(String prefix) throws SAXException {// TODO Auto-generated method stub
        }@Overridepublic void ignorableWhitespace(char[] ch, int start, int length)throws SAXException {// TODO Auto-generated method stub
        }@Overridepublic void processingInstruction(String target, String data)throws SAXException {// TODO Auto-generated method stub
        }@Overridepublic void setDocumentLocator(Locator locator) {// TODO Auto-generated method stub
        }@Overridepublic void skippedEntity(String name) throws SAXException {// TODO Auto-generated method stub
        }@Overridepublic void startPrefixMapping(String prefix, String uri)throws SAXException {// TODO Auto-generated method stub
        }
}

实例二：

SAXDemo2.java

package cn.lsl.sax;import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;//打印第2本书的作者    
public class SAXDemo2 {public static void main(String[] args) throws Exception {SAXParser parser = SAXParserFactory.newInstance().newSAXParser();XMLReader reader = parser.getXMLReader();reader.setContentHandler(new ContentHandler(){    //匿名内部类boolean isAuthor = false;    //是不是作者标签int index = 0;    //作者标签的索引
            @Overridepublic void startElement(String uri, String localName,String qName, Attributes atts) throws SAXException {if("作者".equals(qName)){isAuthor = true;}}@Overridepublic void characters(char[] ch, int start, int length)throws SAXException {if(isAuthor&&index==1){System.out.println(new String(ch,start,length));}}@Overridepublic void endElement(String uri, String localName, String qName)throws SAXException {if("作者".equals(qName)){index++;}isAuthor = false;}@Overridepublic void endDocument() throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void endPrefixMapping(String prefix) throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void ignorableWhitespace(char[] ch, int start, int length)throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void processingInstruction(String target, String data)throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void setDocumentLocator(Locator locator) {// TODO Auto-generated method stub
                }@Overridepublic void skippedEntity(String name) throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void startDocument() throws SAXException {// TODO Auto-generated method stub
                }@Overridepublic void startPrefixMapping(String prefix, String uri)throws SAXException {// TODO Auto-generated method stub
                }});reader.parse("src/book.xml");}
}

实例三：读取XML内容，封装到JavaBean

Book.java

package cn.lsl.domain;public class Book {private String name;private String author;private Double price;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public Double getPrice() {return price;}public void setPrice(Double price) {this.price = price;}@Overridepublic String toString() {return "Book [author=" + author + ", name=" + name + ", price=" + price+ "]";}
}

SAXDemo3.java

package cn.lsl.sax;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.XMLReader;
import org.xml.sax.helpers.DefaultHandler;import cn.lsl.domain.Book;//读取XML内容，封装到JavaBean
public class SAXDemo3 {public static void main(String[] args) throws Exception {SAXParser parser = SAXParserFactory.newInstance().newSAXParser();XMLReader reader =  parser.getXMLReader();final List books = new ArrayList();reader.setContentHandler(new DefaultHandler(){Book book = null;String currentTagName = null;@Overridepublic void startElement(String uri, String localName,String qName, Attributes attributes) throws SAXException {if("书".equals(qName)){book = new Book();}currentTagName = qName;}@Overridepublic void characters(char[] ch, int start, int length)throws SAXException {if("书名".equals(currentTagName)){book.setName(new String(ch,start,length));}if("作者".equals(currentTagName)){book.setAuthor(new String(ch,start,length));}if("售价".equals(currentTagName)){book.setPrice(Double.parseDouble(new String(ch,start,length)));}}@Overridepublic void endElement(String uri, String localName, String qName)throws SAXException {if("书".equals(qName)){books.add(book);book = null;}currentTagName = null;}});reader.parse("src/book.xml");for (Object b:books) {System.out.println(b);}}
}