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());
        }
    }