在上篇文章中，简单介绍了sax解析xml的一种方式，它是继承defaultHandler方式，并重写其中的几个方法来实现的。
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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