AJAX之开发实例介绍
<html><head><title>www.MLDNJAVA.cn</title><script language="javascript"> var xmlHttp ; function createXMLHttp(){ //AJAX创建代码 if(window.XMLHttpRequest){ xmlHttp = new XMLHttpRequest(); //firefox浏览器内核 } else { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } } function checkUserid(userid){ createXMLHttp(); xmlHttp.open("POST","CheckServlet?userid="+userid); xmlHttp.onreadystatechange = checkUseridCallback xmlHttp.send(null); document.getElementById("msg").innerHTML = "正在验证..."; } function checkUseridCallback(){ if(xmlHttp.readyState == 4){ if(xmlHttp.status == 200){ alert("************"); var text = xmlHttp.responseText;if(text == "true"){ document.getElementById("msg").innerHTML = "用户ID重复，无法使用!";} else { document.getElementById("msg").innerHTML = "此用户ID可以注册!";} } } }</script></head><body><form action="regist.jsp" method="post"> 用户ID： <input type="text" name="userid" onblur="checkUserid(this.value)"><span id="msg"></span><br> 姓 名：<input type="text" name="name"><br> 密 码 <input type="password" name="password"><br> <input type="submit" value="注册"> <input type="reset" value="重置"></form></body></html>?
?2,CheckServlet.java
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package org.lxh.ajaxdemo;import java.sql.* ;import java.io.* ;import javax.servlet.* ;import javax.servlet.http.* ;public class CheckServlet extends HttpServlet{public static final String DBDRIVER = "org.gjt.mm.mysql.Driver";public static final String DBURL = "jdbc:mysql://localhost:3306/mldn";public static final String DBUSER = "root" ;public static final String DBPASS = "123456" ;public void doGet(HttpServletRequest request , HttpServletResponse response) throws ServletException,IOException { this.doPost(request,response);}public void doPost(HttpServletRequest request , HttpServletResponse response) throws ServletException,IOException { request.setCharacterEncoding("GBK"); response.setContentType("text/html"); Connection conn = null; PreparedStatement pstmt =null; ResultSet rs = null; PrintWriter out = response.getWriter(); String userid = request.getParameter("userid"); try { Class.forName(DBDRIVER); conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS); String sql = "SELECT COUNT(userid) FROM user WHERE userid=?"; pstmt = conn.prepareStatement(sql); pstmt.setString(1,userid); rs = pstmt.executeQuery(); if(rs.next()){ if(rs.getInt(1) > 0){ out.print("true"); } else { out.print("false"); } }System.out.println("**********************"); }catch(Exception e){ e.printStackTrace(); }finally { try { conn.close(); } catch (Exception e) { } }}};?2,CityServlet.java?
package org.lxh.ajaxdemo ;import java.io.* ;import org.w3c.dom.* ;import javax.xml.parsers.* ;import javax.xml.transform.* ;import javax.xml.transform.dom.* ;import javax.xml.transform.stream.* ;import javax.servlet.* ;import javax.servlet.http.* ;public class CityServlet extends HttpServlet {public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{this.doPost(request,response) ;}public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{response.setContentType("text/xml;charset=GBK") ;PrintWriter out = response.getWriter() ;ByteArrayOutputStream bos = new ByteArrayOutputStream() ;try{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance() ;DocumentBuilder builder = factory.newDocumentBuilder() ;Document doc = builder.newDocument() ;String data[] = {"北京","南京","上海","天津","香港"} ;Element allarea = doc.createElement("allarea") ;for(int x=0;x<data.length;x++){Element area = doc.createElement("area") ;Element id = doc.createElement("id") ;Element title = doc.createElement("title") ;id.appendChild(doc.createTextNode("" + (x+1))) ;title.appendChild(doc.createTextNode(data[x])) ;area.appendChild(id) ;area.appendChild(title) ;allarea.appendChild(area) ;}doc.appendChild(allarea) ;TransformerFactory tf = TransformerFactory.newInstance() ;Transformer t = tf.newTransformer() ;t.setOutputProperty(OutputKeys.ENCODING,"GBK") ;DOMSource source = new DOMSource(doc) ;StreamResult result = new StreamResult(bos) ;t.transform(source,result) ;out.println(bos) ;System.out.println(bos) ;out.close() ;}catch(Exception e){e.printStackTrace() ;}}}??