javaweb学习总结十二(JAXP对XML文档进行SAX解析)

一：JAXP使用SAX方式解析XML文件

1：dom解析与sax解析异同点

2：sax解析特点

二：代码案例

1：xml文件

 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <students>
     <student>
         <name sid="111">李四</name>
         <age>23</age>
         <gender>男</gender>
     </student>
     <student>
         <name sid="222">张三</name>
         <age>21</age>
         <gender>女</gender>
     </student>
 </students>

2：测试主体部分

 @Test
     public void testParseXml() throws ParserConfigurationException,
             SAXException, IOException {
         // 1:获取解析器工厂
         SAXParserFactory factory = SAXParserFactory.newInstance();
         // 2:获取解析器
         SAXParser parser = factory.newSAXParser();
         // 3:获取读取器
         XMLReader reader = parser.getXMLReader();
         // 4:设置内容格式
         reader.setContentHandler(new GetSecondNameHandler());
         // 5:解析文件
         reader.parse("xml/exam.xml");
     }

a:获取整个xml文档标签的处理事件

 // 定义一个解析全文的解析器
 class MyHandler implements ContentHandler {

     @Override
     public void setDocumentLocator(Locator locator) {

     }

     @Override
     public void startDocument() throws SAXException {

     }

     @Override
     public void endDocument() throws SAXException {

     }

     @Override
     public void startPrefixMapping(String prefix, String uri)
             throws SAXException {

     }

     @Override
     public void endPrefixMapping(String prefix) throws SAXException {

     }

     @Override
     public void startElement(String uri, String localName, String qName,
             Attributes atts) throws SAXException {
         System.out.println("<" + qName + ">");
         // 获取元素的属性
         for (int i = 0; i < atts.getLength(); i++) {
             String attrName = atts.getQName(i);
             String attrValue = atts.getValue(i);
             System.out.println(attrName + "=" + attrValue);
         }
     }

     @Override
     public void endElement(String uri, String localName, String qName)
             throws SAXException {
         System.out.println("<" + qName + "/>");
     }

     @Override
     public void characters(char[] ch, int start, int length)
             throws SAXException {
         System.out.println(new String(ch, start, length));
     }

     @Override
     public void ignorableWhitespace(char[] ch, int start, int length)
             throws SAXException {

     }

     @Override
     public void processingInstruction(String target, String data)
             throws SAXException {

     }

     @Override
     public void skippedEntity(String name) throws SAXException {

     }

 }

b：定义“获取指定内容,获取第二个学生的名字”事件

 class GetSecondNameHandler extends DefaultHandler {

     private String contentTag;
     private int currentTag = 0;
     private int getTag = 2;

     @Override
     public void startElement(String uri, String localName, String qName,
             Attributes attributes) throws SAXException {
         contentTag = qName;
     }

     @Override
     public void endElement(String uri, String localName, String qName)
             throws SAXException {
         contentTag = null;
     }

     @Override
     public void characters(char[] ch, int start, int length)
             throws SAXException {
         if ("name".equals(contentTag)) {
             currentTag++;
             if (currentTag == getTag) {
                 System.out.println(new String(ch, start, length));
             }

         }
     }

 }

c:将xml信息封装成javabean对象，然后放到list集合中

 / 将xml中student元素内容封装成对象，然后放到list集合中
 class BeanListHandler extends DefaultHandler {
     private List<Student> list = new ArrayList<Student>();
     private String tagName;
     private Student stu;

     @Override
     public void startElement(String uri, String localName, String qName,
             Attributes attributes) throws SAXException {
         tagName = qName;
         if ("student".equals(tagName)) {
             stu = new Student();
         }
     }

     @Override
     public void characters(char[] ch, int start, int length)
             throws SAXException {

         if ("name".equals(tagName)) {
             stu.setName(new String(ch, start, length));
         }
         if ("age".equals(tagName)) {
             stu.setAge(Integer.parseInt(new String(ch, start, length)));
         }
         if ("gender".equals(tagName)) {
             stu.setGender(new String(ch, start, length));
         }

     }

     @Override
     public void endElement(String uri, String localName, String qName)
             throws SAXException {
         if ("student".equals(qName)) {
             list.add(stu);
             stu = null;
         }

         tagName = null;
     }

     public List<Student> getStudents() {
         return list;
     }

 }

测试程序代码修改为：

 @Test
     public void testParseXml() throws ParserConfigurationException,
             SAXException, IOException {
         // 1:获取解析器工厂
         SAXParserFactory factory = SAXParserFactory.newInstance();
         // 2:获取解析器
         SAXParser parser = factory.newSAXParser();
         // 3:获取读取器
         XMLReader reader = parser.getXMLReader();
         // 4:设置内容格式
         BeanListHandler beanListHandler = new BeanListHandler();
         reader.setContentHandler(beanListHandler);
         // 5:解析文件
         reader.parse("xml/exam.xml");

         List<Student> list = beanListHandler.getStudents();
         for (Student stu : list) {
             System.out.println("name=" + stu.getName() + "  age=" + stu.getAge()
                     + " gender=" + stu.getGender());
         }
     }