接下来说的第二种方式是用RootElement这个类来解析的，RootElement 内置了defaultHandler的子类，
RootElement 源码如下：
public class RootElement extends Element { final Handler handler = new Handler(); /** * Constructs a new root element with the given name. * * @param uri the namespace * @param localName the local name */ public RootElement(String uri, String localName) { super(null, uri, localName, 0); } /** * Constructs a new root element with the given name. Uses an empty string * as the namespace. * * @param localName the local name */ public RootElement(String localName) { this("", localName); } /** * Gets the SAX {@code ContentHandler}. Pass this to your SAX parser. */ public ContentHandler getContentHandler() { return this.handler; } class Handler extends DefaultHandler { Locator locator; int depth = -1; Element current = null; StringBuilder bodyBuilder = null; @Override public void setDocumentLocator(Locator locator) { this.locator = locator; } @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { int depth = ++this.depth; if (depth == 0) { // This is the root element. startRoot(uri, localName, attributes); return; } // Prohibit mixed text and elements. if (bodyBuilder != null) { throw new BadXmlException("Encountered mixed content" + " within text element named " + current + ".", locator); } // If we're one level below the current element. if (depth == current.depth + 1) { // Look for a child to push onto the stack. Children children = current.children; if (children != null) { Element child = children.get(uri, localName); if (child != null) { start(child, attributes); } } } } void startRoot(String uri, String localName, Attributes attributes) throws SAXException { Element root = RootElement.this; if (root.uri.compareTo(uri) != 0 || root.localName.compareTo(localName) != 0) { throw new BadXmlException("Root element name does" + " not match. Expected: " + root + ", Got: " + Element.toString(uri, localName), locator); } start(root, attributes); } void start(Element e, Attributes attributes) { // Push element onto the stack. this.current = e; if (e.startElementListener != null) { e.startElementListener.start(attributes); } if (e.endTextElementListener != null) { this.bodyBuilder = new StringBuilder(); } e.resetRequiredChildren(); e.visited = true; } @Override public void characters(char[] buffer, int start, int length) throws SAXException { if (bodyBuilder != null) { bodyBuilder.append(buffer, start, length); } } @Override public void endElement(String uri, String localName, String qName) throws SAXException { Element current = this.current; // If we've ended the current element... if (depth == current.depth) { current.checkRequiredChildren(locator); // Invoke end element listener. if (current.endElementListener != null) { current.endElementListener.end(); } // Invoke end text element listener. if (bodyBuilder != null) { String body = bodyBuilder.toString(); bodyBuilder = null; // We can assume that this listener is present. current.endTextElementListener.end(body); } // Pop element off the stack. this.current = current.parent; } depth--; } } }以上是RootElement类得源码，从源码可以看出，它只是将defaultHandler简单的处理一下。
具体应用可以参照我写的测试源码
/** * sax解析xml的第二种方式 * 用XMLReader 也是sax的一种方式 * @return */ private String saxParseSecond(){ //读取src下xml文件 InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("saxTest.xml"); SAXParserFactory factory = SAXParserFactory.newInstance(); try { SAXParser parse = factory.newSAXParser(); XMLReader reader = parse.getXMLReader(); reader.setContentHandler(getRootElement().getContentHandler()); reader.parse(new InputSource(inputStream)); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return result; }/** * * @return 返回设置好处理机制的rootElement */ private RootElement getRootElement(){ /*rootElement代表着根节点，参数为根节点的tagName*/ RootElement rootElement = new RootElement("classes"); /*获取一类子节点，并为其设置相应的事件 * 这里需要注意，虽然我们只设置了一次group的事件，但是我们文档中根节点下的所有 * group却都可以触发这个事件。 * */ Element groupElement = rootElement.getChild("group"); // 读到元素开始位置时触发，如读到<group>时 groupElement.setStartElementListener(new StartElementListener() { @Override public void start(Attributes attributes) { // Log.i("TEST", "start"); String groupName = attributes.getValue("name"); String groupNum = attributes.getValue("num"); result = result+"groupName ="+groupName+"groupNum = "+groupNum+"\n"; } }); //读到元素结束位置时触发，如读到</group>时 groupElement.setEndElementListener(new EndElementListener() { @Override public void end() { } }); Element personElement = groupElement.getChild("person"); //读取<person>标签触发 personElement.setStartElementListener(new StartElementListener() { @Override public void start(Attributes attributes) { String personName = attributes.getValue("name"); String age = attributes.getValue("age"); result = result+"personName ="+personName+"age = "+age+"\n"; } }); //读取</person>标签触发 personElement.setEndElementListener(new EndElementListener() { @Override public void end() { } }); Element chinese = personElement.getChild("chinese"); // chinese.setTextElementListener(new TextElementListener() { // // @Override // public void end(String body) { // // TODO Auto-generated method stub // // } // // @Override // public void start(Attributes attributes) { // // TODO Auto-generated method stub // // } // }); // 读到文本的末尾时触发,这里的body即为文本的内容部分 chinese.setEndTextElementListener(new EndTextElementListener() { @Override public void end(String body) { Pattern p = Pattern.compile("\\s*|\t|\r|\n"); Matcher m = p.matcher(body); body = m.replaceAll(""); result = result+"chinese ="+body; } }); Element english = personElement.getChild("english"); english.setEndTextElementListener(new EndTextElementListener() { @Override public void end(String body) { Pattern p = Pattern.compile("\\s*|\t|\r|\n"); Matcher m = p.matcher(body); body = m.replaceAll(""); result = result+"english ="+body+"\n"; } }); return rootElement; }
我们都知道通过SAXParser对象解析xml的方式，这里我们又从代码中看到了利用另一个对象XMLReader进行解析，那么两者到底有什么联系和区别呢？
其实SAXParser是在SAX 1.0 定义的，而XMLReader则是在2.0中才开始出现的。你可以认为XMLReader的出现是为了替代SAXParser解析的，两者本质上干的事情是一样的，只不过XMLReader的功能更加的强悍而已。
关于XMLReader的获取方式，除了通过SAXParser的getXMLReader方法获得之外，我们还可以通过以下两种方式。
XMLReader parser=XMLReaderFactory.createXMLReader(); (1)XMLReader parser=XMLReaderFactory.createXMLReader(String className); (2)
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