Java使用SAM解析XML

上一篇文章中讲述了如何使用DOM解析XML，这篇文章讲一下使用SAM（Simple API for XML）解析XML.

XML文件如下：

<?xml version="1.0" encoding="UTF-8"?><books><book id="1"><name>java入门</name><price>35.9</price></book><book id="2"><name>java精通</name><price>89.6</price></book></books>

创建三个类

Book.java

public class Book {      private int id;      private String name;      private float price;      public int getId() {          return id;      }      public void setId(int id) {          this.id = id;      }      public String getName() {          return name;      }      public void setName(String name) {          this.name = name;      }      public float getPrice() {          return price;      }      public void setPrice(float price) {          this.price = price;      }      @Override      public String toString(){          return "Id is :"+this.id+"; Name is:"+this.name+"; Price is:"+this.price;      }  }

SAXTool.java

 

public class SAXTool { public SAXTool() {// TODO Auto-generated constructor stub}public List <Book> getBookList(InputStream xmlStream) throws Exception {// TODO Auto-generated constructor stub//获取SAXFactory实例SAXParserFactory factory = SAXParserFactory.newInstance();//通过factory获取SAXParserSAXParser parser = factory.newSAXParser();//实例化一个解析工具SAXUtil handler = new SAXUtil();//解析文件/*SAX解析是边读边解析，所以读到一个element要素 *就回调handler中重写的相关方法*/parser.parse(xmlStream, handler);return handler.getBookList();} }

SAXUtil.java

public class SAXUtil extends DefaultHandler {private List<Book> booklist = null;private Book book;private String preTag = null;// 作用是记录解析时的上一个节点名称public SAXUtil() {// TODO Auto-generated constructor stub}public List<Book> getBookList(){return booklist;}@Overridepublic void startDocument() throws SAXException {booklist = new ArrayList<Book>();}/** * 收到一个元素开始的通知 * Receive notification of the start of an element. * * <p> * By default, do nothing. Application writers may override this method in a * subclass to take specific actions at the start of each element (such as * allocating a new tree node or writing output to a file). * </p> * * @param uri *            The Namespace URI, or the empty string if the element has no *            Namespace URI or if Namespace processing is not being *            performed. * @param localName *            The local name (without prefix), or the empty string if *            Namespace processing is not being performed. * @param qName *            The qualified name (with prefix), or the empty string if *            qualified names are not available. * @param attributes *            The attributes attached to the element. If there are no *            attributes, it shall be an empty Attributes object. * @exception org.xml.sax.SAXException *                Any SAX exception, possibly wrapping another exception. * @see org.xml.sax.ContentHandler#startElement */@Overridepublic void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {// no opif ("book".equals(qName)) {book = new Book();book.setId(Integer.parseInt(attributes.getValue(0)));}preTag = qName;}/** * 收到一个字符数据通知 * Receive notification of character data inside an element. * * <p> * By default, do nothing. Application writers may override this method to * take specific actions for each chunk of character data (such as adding * the data to a node or buffer, or printing it to a file). * </p> * * @param ch *            The characters. * @param start *            The start position in the character array. * @param length *            The number of characters to use from the character array. * @exception org.xml.sax.SAXException *                Any SAX exception, possibly wrapping another exception. * @see org.xml.sax.ContentHandler#characters */@Overridepublic void characters(char[] ch, int start, int length) throws SAXException {if (preTag != null) {String content = new String(ch, start, length);if ("name".equals(preTag)) {book.setName(content);} else if ("price".equals(preTag)) {book.setPrice(Float.parseFloat(content));}}}/** * 收到一个元素结束的通知 * Receive notification of the end of an element. * * <p> * By default, do nothing. Application writers may override this method in a * subclass to take specific actions at the end of each element (such as * finalising a tree node or writing output to a file). * </p> * * @param uri *            The Namespace URI, or the empty string if the element has no *            Namespace URI or if Namespace processing is not being *            performed. * @param localName *            The local name (without prefix), or the empty string if *            Namespace processing is not being performed. * @param qName *            The qualified name (with prefix), or the empty string if *            qualified names are not available. * @exception org.xml.sax.SAXException *                Any SAX exception, possibly wrapping another exception. * @see org.xml.sax.ContentHandler#endElement */@Overridepublic void endElement(String uri, String localName, String qName) throws SAXException {if ("book".equals(qName)) {booklist.add(book);book = null;}preTag = null;/** * 当解析结束时置为空。这里很重要，例如，当图中画3的位置结束后，会调用这个方法 * ，如果这里不把preTag置为null，根据startElement(....)方法， * preTag的值还是book，当文档顺序读到图 中标记4的位置时，会执行characters(char[] * ch, int start, int length)这个方法，而characters(....)方 * 法判断preTag!=null，会执行if判断的代码，这样就会把空值赋值给book，这不是我们想要的。 */}}

 

在调用方法:

try {InputStream fins = new FileInputStream("book.xml");SAXTool Saxtool = new SAXTool();List<Book> booklist = (List<Book>) Saxtool.getBookList(fins);for (Book book : booklist) {System.out.println(book.toString());}} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}

输出结果: