利用Ajax把前端的数据封装成JSON格式发送到服务器端并写成XML格式在服务器的硬盘上

时间：2022-08-04 05:52:09

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:\n " + 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：
利用Ajax把前端的数据封装成JSON格式发送到服务器端并写成XML格式在服务器的硬盘上

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();

        }

    }

}

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