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利用jaxp dom 实现 ajax xml 响应

在某些情况下用 jaxp dom api 实现ajax xml响应会是一个很好的选择,可以简化程序.需要用到的jar包javax.xml.parsers.*; org.w3c.dom.*;javax.xml.transform.*;javax.xml.transform.stream.*;javax.xml.transform.dom.*;
前两个包用来创建xml文档,后面几个用来转换到输出流. 以下简要说明用到的方法.然后贴出一个完整实例.
创建新文档             DocumentBuilderFactory factory = DocumentBuilderFactory.
                                             newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
           
            Document doc = builder.newDocument();
创建root元素 或其它元素            Element root = doc.createElement("selects");
创建根元素                doc.appendChild(root);  Element的appendChild()方法用来添加子元素
创建文本结点          doc.createTextNode(String textNode)
在servlet中 通过以下方法转换到输出流            Transformer t = TransformerFactory.newInstance().newTransformer();            t.transform(new DOMSource(doc),
                        new StreamResult(response.getWriter()));



web.inf 文件配置一个servlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2eehttp://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4">
  <display-name>WebModule1</display-name>
  <servlet>
    <servlet-name>selectservlet</servlet-name>
    <servlet-class>drownmenu.SelectServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>selectservlet</servlet-name>
    <url-pattern>/selectservlet</url-pattern>
  </servlet-mapping>
</web-app>

jsp页面
<%@ page language="java" contentType="text/html; charset=utf-8"%>

<html>
  <head>
    <title>Ajax 联动下拉框</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <SCRIPT type="text/javascript">
        var req;
        window.onload=function(){
        }

        function Change_Select()
        {
            var zhi=document.getElementById('state').value;
            var url="selectservlet?id="+escape(zhi);
            if(window.XMLHttpRequest)
            {
                req=new XMLHttpRequest();
            }else if(window.ActiveXObject)
            {
                req=new ActiveXObject("Microsoft.XMLHTTP");
            }

            if(req)
            {
                req.open("GET",url,true);
                req.onreadystatechange=callback;
                req.send(null);
            }
        }

        function callback()
        {
            if(req.readyState == 4)
            {
                if(req.status == 200)
                {
                    parseMessage();
                }else{
                    alert("Not able to retrieve description"+req.statusText);
                }
            }
        }

        function parseMessage()
        {
            var xmlDoc=req.responseXML.documentElement;
            var xSel=xmlDoc.getElementsByTagName('select');
            var select_root=document.getElementById('city');
            select_root.options.length=0;

            for(var i=0;i<xSel.length;i++)
            {
                var xValue=xSel[i].childNodes[0].firstChild.nodeValue;
                var xText=xSel[i].childNodes[1].firstChild.nodeValue;
                var option=new Option(xText,xValue);
                try{
                    select_root.add(option);
                }catch(e){
                }
            }


        }
    </SCRIPT>
  </head>

  <body>
    <div align="center">
        <form name="form1" method="post" action="">
            <TABLE width="70%" boder="0" cellspacing="0">
                <TR>
                    <TD align="center">Ajax 联动下拉框</TD>
                </TR>
                <TR>
                    <TD>请选择省份:
                        <SELECT name="state" id="state" onChange="Change_Select()">
                            <OPTION value="0">未选择</OPTION>
                            <OPTION value="1">湖南</OPTION>
                            <OPTION value="2">湖北</OPTION>

                        </SELECT>
                        请选择城市:
                        <SELECT name="city" id="city">
                            <OPTION value="0">未选择</OPTION>
                        </SELECT>
                    </TD>
                </TR>
                <TR><td>&nbsp;</td></TR>
            </TABLE>
        </form>
    </div>
  </body>
</html>

SelectServlet 类
package drownmenu;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import javax.xml.transform.*;
import javax.xml.transform.stream.*;
import javax.xml.transform.dom.*;


public class SelectServlet extends HttpServlet {

    //Initialize global variables
    public void init() throws ServletException {
    }

    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {

        String targetId = request.getParameter("id").toString();
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/xml");
        try {
            DocumentBuilderFactory factory = DocumentBuilderFactory.
                                             newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
           
            Document doc = builder.newDocument();
         
            Element root = doc.createElement("selects");
            doc.appendChild(root);

            /*
                        String xml_start="<selects>";
                        String xml_end="</selects>";
                        String xml="";*/
            if (targetId.equalsIgnoreCase("0")) {

                makeElement(doc, root, new String[] {"未选择"});
                // xml =    "<select><value>0</value><text>Unbounded</text></select>";
            }
            if (targetId.equalsIgnoreCase("1")) {
                makeElement(doc, root, new String[]  {"长沙","岳阳"});


                /* xml =
                 "<select><value>1</value><text>Mana Burn</text></select>";
                 xml +=
                 "<select><value>2</value><text>Death Coil</text></select>";
                 xml +=
                 "<select><value>3</value><text>Unholy Aura</text></select>";
                 xml +=
                 "<select><value>4</value><text>Unholy Fire</text></select>";
                 */
            }
            if (targetId.equalsIgnoreCase("2")) {
                makeElement(doc, root, new String[] {"武汉","石堰","襄樊","孝感"});
                /*
                  xml =
                 "<select><value>1</value><text>Corprxplode</text></select>";
                  xml +=
                 "<select><value>2</value><text>Raise Dead</text></select>";
                  xml +=
                 "<select><value>3</value><text>Brilliance Aura</text></select>";
                  xml +=
                 "<select><value>4</value><text>Aim Aura</text></select>";
                 */
            } //else {
             
                /*
                   xml =
                 "<select><value>1</value><text>Rain of Chaos</text></select>";
                   xml +=
                 "<select><value>2</value><text>Finger of Death</text></select>";
                 xml += "<select><value>3</value><text>Bash</text></select>";
                   xml +=
                 "<select><value>4</value><text>Summon Doom</text></select>";
                 */
         //   }
      
            Transformer t = TransformerFactory.newInstance().newTransformer();

            t.transform(new DOMSource(doc),
                        new StreamResult(response.getWriter()));

        } catch (Exception ex) {
            throw new ServletException(ex.toString());
        }
        // String last_xml = xml_start + xml + xml_end;
        // response.getWriter().write(last_xml);
    }

    private void makeElement(Document doc, Element root, String[] name) throws
            DOMException {
        if (name == null) {
            return;
        }

        for (int i = 0; i < name.length; i++) {
            Element selectElement = doc.createElement("select");

            root.appendChild(selectElement);

            Element valueElement = doc.createElement("value");
            Element textElement = doc.createElement("text");
            int t=i+1;
            Text valueText = doc.createTextNode(""+t);           
            Text textText = doc.createTextNode(name[i]);
            valueElement.appendChild(valueText);
            textElement.appendChild(textText);
            selectElement.appendChild(valueElement);
            selectElement.appendChild(textElement);
           

        }

    }

    //Process the HTTP Post request
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }

    //Clean up resources
    public void destroy() {
    }
}


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posted on 2006-06-29 16:06 傻 瓜 阅读(2422) 评论(0)  编辑  收藏 所属分类: Ajax


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