1.首先要在前端把要发送的东西（这里是一个实例化的car对象）都准备好，利用Ajax发送到服务器端,代码如下：
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>JSON Example</title> <script type="text/javascript" src="json.js"></script> <script type="text/javascript"> var xmlHttp; function createXMLHttpRequest() { if (window.ActiveXObject) { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) { xmlHttp = new XMLHttpRequest(); } } function doJSON() { var car = getCarObject();//得到实例化的对象 //Use the JSON JavaScript library to stringify the Car object var carAsJSON = JSON.stringify(car); alert("Car object as JSON: " + carAsJSON); //发送到服务器端的时候会去找lib/web,xml下的映射，通过映射来调用对应的servlet var url = "hello"; createXMLHttpRequest(); xmlHttp.open("POST", url, true); xmlHttp.onreadystatechange = handleStateChange; xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;"); xmlHttp.send(carAsJSON); } //回调函数 function handleStateChange() { alert("xmlHttp.readyState"+xmlHttp.readyState); if(xmlHttp.readyState == 4) { alert("xmlHttp.status"+xmlHttp.status); if(xmlHttp.status == 200) { parseResults(); } } } function parseResults() { var responseDiv = document.getElementById("serverResponse"); if(responseDiv.hasChildNodes()) { responseDiv.removeChild(responseDiv.childNodes[0]); } var responseText = document.createTextNode(xmlHttp.responseText); responseDiv.appendChild(responseText); } //实例化car function getCarObject() { return new Car("Dodge", "Coronet R/T", 1968, "yellow"); } //先要定义一个car类，才能实例化 function Car(make, model, year, color) { this.make = make; this.model = model; this.year = year; this.color = color; } </script> </head> <body> <form action="#"> <input type="button" value="Click here to send JSON data to the server" onclick="doJSON();"/> </form> <h2>Server Response:</h2> <div id="serverResponse"></div> </body> </html>
2.以上的代码是把数据发送到服务器了，下面服务器要接收，处理发送过来的数据了，通过lib/web.xml来找到处理的对应的servlet，服务器端嘛，肯定要用servlet来处理的
web.xml的映射如下：即通过映射调用JSONExample这个servlet来处理
<servlet>
<servlet-name>JSONExample</servlet-name>
<servlet-class>JSONExample</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>JSONExample</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
3.要使JSONExample能工作还需要导入如下包：
4. 请求到来后先调用doPost方法，用readJSONStringFromRequestBody获得发送过来的字符串，再把字符串变为json对象jsonObject = new JSONObject(json)，
然后调用writeXMLFile("C:\hello.xml")来建立xml文档并写到C盘上一个叫做hello.xml的xml的格式的文件（自动生成的，不用自己创建，如果C盘本来就有这个相同的文件名在，则会删掉里面原来的内容并更新新的内容）
import java.io.*; import java.net.*; import java.text.ParseException; import javax.servlet.*; import javax.servlet.http.*; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStreamWriter; import java.util.Vector; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import org.apache.crimson.tree.XmlDocument; import org.w3c.dom.Attr; import org.w3c.dom.DOMException; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.NamedNodeMap; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Text; import org.json.JSONException; import org.json.JSONObject; public class JSONExample extends HttpServlet { private static final long serialVersionUID = 1L; JSONObject jsonObject = null; public JSONExample() { super(); // TODO Auto-generated constructor stub } public void writeXMLFile(String outFile) throws Exception { //为解析XML作准备，创建DocumentBuilderFactory实例,指定DocumentBuilder DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = null; try { db = dbf.newDocumentBuilder(); } catch (ParserConfigurationException pce) { System.err.println(pce); System.exit(1); } Document doc = null; doc = db.newDocument(); //下面是建立XML文档内容的过程，建立根节点car Element root = doc.createElement("car"); //把car这个根节点放到doc里面去 doc.appendChild(root); //建立一个节点叫make,其中element1 表示这是root下面的第一个节 Element element1 = doc.createElement("make"); //把节点名为make的这个节点插入到root这个根节点后面 root.appendChild(element1 ); //获得make这个节点的具体内容 Text tName = doc.createTextNode(jsonObject.getString("make")); //把make这个节点的具体内容插入到节点名为make的下面 element1 .appendChild(tName); //创建第二个节点 Element element2= doc.createElement("model"); //把第二个节点插入到root后面和第一个节点是兄弟关系 root.appendChild(element2); Text tAge = doc.createTextNode(jsonObject.getString("model")); element2.appendChild(tAge); //把第三个节点插入到root后面和第一个节点是兄弟关系 Element element3= doc.createElement("year"); root.appendChild(element3); Text tPhone = doc.createTextNode(jsonObject.getString("year")); element3.appendChild(tPhone); //把第四个节点插入到root后面和第一个节点是兄弟关系 Element element4= doc.createElement("color"); root.appendChild(element4); Text tColor = doc.createTextNode(jsonObject.getString("color")); element4.appendChild(tColor); System.out.println(2); //把XML文档输出到指定的文件 FileOutputStream outStream = new FileOutputStream(outFile); OutputStreamWriter outWriter = new OutputStreamWriter(outStream); ((XmlDocument) doc).write(outWriter, "GB2312"); outWriter.close(); outStream.close(); } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } private String readJSONStringFromRequestBody(HttpServletRequest request){ StringBuffer json = new StringBuffer(); String line = null; try { BufferedReader reader = request.getReader(); while((line = reader.readLine()) != null) { json.append(line); } } catch(Exception e) { System.out.println("Error reading JSON string: " + e.toString()); } return json.toString(); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String json = readJSONStringFromRequestBody(request); //Use the JSON-Java binding library to create a JSON object in Java try { jsonObject = new JSONObject(json); } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } //---------------------------------- System.out.println(3); try { System.out.println(4); writeXMLFile("C:\hello.xml"); System.out.println(5); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }