本文實例為大家分享了ajax實現驗證碼功能的具體代碼，供大家參考，具體內容如下
首先創建一個驗證碼：
<%@ page contentType="image/jpeg; charset=utf-8" language="java" import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*" pageEncoding="UTF-8"%> <!-- 以上導入awt和awt.image包 --> <%! //獲取隨機顏色 public Color getColor(){ Random random = new Random(); //使用rgb()隨機產生顏色 int r = random.nextInt(256); int g = random.nextInt(256); int b = random.nextInt(256); return new Color(r,g,b); } //獲取隨機數字 產生一個4位數 public String getNum(){ String str = ""; Random random = new Random(); for(int i = 0;i < 4;i++){ str += random.nextInt(10); //0-9 } return str; } %> <% /* 清除緩存 */ response.setHeader("pragma", "mo-cache"); response.setHeader("cache-control", "no-cache"); response.setDateHeader("expires", 0); //產生矩形框 BufferedImage image = new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB); //獲取畫筆工具 Graphics g = image.getGraphics(); //設置矩形框的顏色 g.setColor(new Color(200,200,200)); //設置坐標和寬高 g.fillRect(0, 0, 80, 30); //隨機產生干擾線 for(int i = 0;i < 30;i++){ Random random = new Random(); int x = random.nextInt(80); int y = random.nextInt(30); int x1 = random.nextInt(x + 10); int y1 = random.nextInt(y + 10); //設置隨機顏色 g.setColor(getColor()); //畫出來 g.drawLine(x, y, x1, y1); } //字的顏色和數字 g.setFont(new Font("Microsoft YaHei",Font.BOLD,16)); g.setColor(Color.BLACK); //獲取隨機數字 String checkNum = getNum(); //給字拼接空格 StringBuffer sb = new StringBuffer(); for(int i = 0;i < checkNum.length();i++){ sb.append(checkNum.charAt(i) + " "); } //畫出數字 g.drawString(sb.toString(), 15, 20); //存入session域中 session.setAttribute("CHECKNUM", checkNum); //例如1010 //將圖像以jpeg的形式通過字節流輸出 ImageIO.write(image, "jpeg", response.getOutputStream()); //清除緩存 out.clear(); //放入body中 out = pageContext.pushBody(); %> 將驗證碼壓縮成圖片，在checkcode.jsp中引用,并在該頁面中利用ajax向服務器發送數據
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>" rel="external nofollow" > <title>驗證碼</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <style type="text/css"> table{ margin: 100px auto; } </style> </head> <body> <table border="0" align="center"> <tr> <td>驗證碼</td> <td><input type="text" name="checkcode" id="checkcodeID" maxlength="4" size="4"></td> <td><img alt="加載失敗" src="image.jsp"></td> <td id="show">√√√</td> </tr> </table> </body> <script type="text/javascript"> //去除空格 function trim(str){ //從左側開始替換空格 str = str.replace(/^/s*/,""); //從左側開始替換空格 str = str.replace(//s$/,""); return str; } </script> <script type="text/javascript"> //創建ajax對象 function createAjax(){ var ajax = null; try{ ajax = new ActiveXObject("microsoft.xmlhttp"); }catch(e){ try{ ajax = new XMLHttpRequest(); }catch(e1){ alert("請更換瀏覽器"); } } return ajax; } </script> <script type="text/javascript"> document.getElementById("checkcodeID").onkeyup = function(){ var checkcode = this.value; //去除空格 checkcode = trim(checkcode); if(checkcode.length == 4){ //獲取ajax對象 var ajax = createAjax(); //獲取去空格的內容 var method = "POST"; var url = "${pageContext.request.contextPath}/CheckcodeServlet?time="+new Date().getTime(); //準備發送異步請求 ajax.open(method, url); //設置請求頭POST提交方式才需要 ajax.setRequestHeader("content-type", "application/x-www-form-urlencoded"); //拼接實體內容 var content = "checkcode=" + checkcode; //發送請求 ajax.send(content); //監聽服務器狀態變化 ajax.onreadystatechange = function(){ if(ajax.readyState == 4){ if(ajax.status == 200){ //獲取服務器內容 var tip = ajax.responseText; //獲取圖片路徑 然后進行放入td中 var img = document.createElement("img"); img.src = tip; img.style.width = "14px"; img.style.height = "14px"; var td = document.getElementById("show"); td.innerHTML = ""; td.appendChild(img); } } } } } </script> </html>
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