一个字符串 <message>HELLO!</message>,怎样解析得到HELLO！?
正则表达式可以轻松解决，但是节点多了就搞不定了。

1、使用JDOM

String xml = "<message>HELLO!</message>";
org.jdom.input.SAXBuilder saxBuilder = new SAXBuilder();
try {
    org.jdom.Document doc = saxBuilder.build(new StringReader(xml));
    String message = doc.getRootElement().getText();
    System.out.println(message);
} catch (JDOMException e) {
    // handle JDOMException
} catch (IOException e) {
    // handle IOException
}

2、使用Xerces DOMParser

String xml = "<message>HELLO!</message>";
DOMParser parser = new DOMParser();
try {
    parser.parse(new InputSource(new java.io.StringReader(xml)));
    Document doc = parser.getDocument();
    String message = doc.getDocumentElement().getTextContent();
    System.out.println(message);
} catch (SAXException e) {
    // handle SAXException 
} catch (IOException e) {
    // handle IOException 
}

3、使用 JAXP

String xml = "<message>HELLO!</message>";
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = null;
try {
    db = dbf.newDocumentBuilder();
    InputSource is = new InputSource();
    is.setCharacterStream(new StringReader(xml));
    try {
        Document doc = db.parse(is);
        String message = doc.getDocumentElement().getTextContent();
        System.out.println(message);
    } catch (SAXException e) {
        // handle SAXException
    } catch (IOException e) {
        // handle IOException
    }
} catch (ParserConfigurationException e1) {
    // handle ParserConfigurationException
}

4、使用JAXB

包
import java.io.StringReader;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;


String xmlString = "<message>HELLO!</message> ";
JAXBContext jc = JAXBContext.newInstance(String.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
StreamSource xmlSource = new StreamSource(new StringReader(xmlString));
JAXBElement<String> je = unmarshaller.unmarshal(xmlSource, String.class);
System.out.println(je.getValue());

5、使用jdk自带功能

String msg = "<message>HELLO!</message>";
DocumentBuilder newDocumentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document parse = newDocumentBuilder.parse(new ByteArrayInputStream(msg.getBytes()));
System.out.println(parse.getFirstChild().getTextContent());