用Java自带API解析XML字符串和生成XML字符串的例子

Parse XML String and create XML String Sample Using Java DOM API

package g002.javaxmltest;

import java.io.ByteArrayInputStream;
import java.io.StringWriter;
import java.nio.charset.Charset;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
* Parse and create xml string using java xml api.
*
* @author kaige
*/
public class JDomTest {

private static XPath xPath;
private static DocumentBuilder docbuilder;
private static DocumentBuilderFactory dbfactory;
private static DocumentBuilderFactory bFactory;
private static DocumentBuilder builder;
private static TransformerFactory tfactory;
private static Transformer transformer;

public static void main(String[] args) throws Throwable {

dbfactory = DocumentBuilderFactory.newInstance();
docbuilder = dbfactory.newDocumentBuilder();
xPath = XPathFactory.newInstance().newXPath();
bFactory = DocumentBuilderFactory.newInstance();
builder = bFactory.newDocumentBuilder();
tfactory = TransformerFactory.newInstance();
transformer = tfactory.newTransformer();

System.out.println("--------------------jdom parse xml test--------------------");
parseXml();

System.out.println("--------------------jdom create xml test--------------------");
createXml();
}

/**
* Java Dom parse xml test
* @throws Throwable
*/
static void parseXml() throws Throwable {

String xml = "<?xml version='1.0' encoding='UTF-8'?>"
+ "<employees>"
+ "<employee id='0001' type='staff'>"
+ "<fields>"
+ "<field name='name' depth='1'>s001</field>"
+ "<field name='sex' depth='2'>1</field>"
+ "<field name='mail' depth='3'>s001@xxx.com</field>"
+ "</fields>"
+ "</employee>"
+ "<employee id='0002' type='leader'>"
+ "<fields>"
+ "<field name='name' depth='1'>s002</field>"
+ "<field name='sex' depth='2'>2</field>"
+ "<field name='mail' depth='3'>s002@xxx.com</field>"
+ "</fields>"
+ "</employee>"
+ "<employee id='0003' type='ceo'>"
+ "<fields>"
+ "<field name='name' depth='1'>s003</field>"
+ "<field name='sex' depth='2'>1</field>"
+ "<field name='mail' depth='3'>s003@xxx.com</field>"
+ "</fields>"
+ "</employee>"
+ "</employees>";

Document doc = docbuilder.parse(new ByteArrayInputStream(xml
.getBytes(Charset.defaultCharset())));

String expression = "employees/employee[@type='staff']|employees/employee[@type='leader']";

NodeList nodeList = selectNodeList(doc, expression);

for (int i = 0; i < nodeList.getLength(); i++) {
Element node = (Element) nodeList.item(i);
System.out.println(node.getAttribute("id"));

NodeList childrenNodeList = selectNodeList(node,
"fields/field[@depth>2]");
for (int j = 0; j < childrenNodeList.getLength(); j++) {
Element child = (Element) childrenNodeList.item(j);

System.out.print(child.getAttribute("name"));
System.out.print("-->");
System.out.println(child.getTextContent());
}
}

System.out.println("Select a single node-----------------");
Node singleNode = selectSingleNode(doc, "/employees/employee/fields/field[.='s001']");
System.out.println(singleNode.getTextContent());

}

/**
* Select multiple nodes from a parent node.
* @param item Parent node
* @param xpath XPath expression
* @return Result
* @throws Throwable Exception
*/
private static NodeList selectNodeList(Object item, String xpath) throws Throwable {

return (NodeList) xPath.compile(xpath).evaluate(item, XPathConstants.NODESET);
}

/**
* Select a single node from a parent node.
* @param item Parent node
* @param xpath XPath expression
* @return Result
* @throws Throwable Exception
*/
private static Node selectSingleNode(Object item, String xpath) throws Throwable {

return (Node) xPath.compile(xpath).evaluate(item, XPathConstants.NODE);
}

/**
* Create XML document.
* @throws Throwable
*/
static void createXml() throws Throwable {

Document doc = builder.newDocument();

Element root = doc.createElement("employees");
doc.appendChild(root);

Element elemObject = doc.createElement("employee");
root.appendChild(elemObject);
elemObject.setAttribute("id", "s001");
elemObject.setAttribute("type", "staff");
Element elemFields = doc.createElement("fields");
elemObject.appendChild(elemFields);
Element elemField01 = doc.createElement("field");
elemFields.appendChild(elemField01);
elemField01.setAttribute("name", "name");
elemField01.setAttribute("depth", "1");
elemField01.setTextContent("staff 001");

// create a StringWriter for the output
StringWriter outWriter = new StringWriter();
StreamResult result = new StreamResult(outWriter);
transformer.transform(new DOMSource(root), result);
String resXml = outWriter.getBuffer().toString();

// transformer.setOutputProperty("encoding", "UTF-8");
System.out.println(resXml);

}
}