在注册、登录的页面上经常会出现验证码，为了防止频繁的注册或登录行为。下面是我用java制作的一个验证码，供初学者参考，做完验证码之后，我们可以用ajax进行验证码验证。
功能一：验证码制作的代码，点击图片，验证码进行更换
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/**
* 显示验证码图片
*/
public void showCheckCode(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 调用业务逻辑
String checkCode = getCheckCode();
//将验证码字符放入session域对象中
req.getSession().setAttribute("checkCode", checkCode);
//图片宽
int width = 80;
//图片高
int height = 30;
//在内存中创建一个图片
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//获取一个画笔
Graphics g = image.getGraphics();
//设置画笔颜色，用灰色做背景
g.setColor(Color.GRAY);
//向Image中填充灰色
g.fillRect(0,0,width,height);
Random r = new Random();
//设置3条干扰线
for (int i = 0; i < 3; i++) {
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
g.drawLine(r.nextInt(80), r.nextInt(30), r.nextInt(80), r.nextInt(80));
}
//设置验证码字符串的颜色
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
//设置字符的大小
g.setFont(new Font("黑体",Font.BOLD,24));
//在图片中写入验证码字符串
g.drawString(checkCode,15,20);
//将Image对象以PNG格式输出给所有的客户端
ImageIO.write(image,"PNG",resp.getOutputStream());
}
/**
* 获取4位验证码中的4位随机字符串
*/
public static String getCheckCode(){
//验证码中的字符由数字和大小写字母组成
String code = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
Random r = new Random();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < 4; i++) {
sb.append(code.charAt(r.nextInt(code.length())));
}
return sb.toString();
}
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jsp页面
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<script type="text/javascript">
function changeCodeImage(img){
img.src = "${pageContext.request.contextPath}/UserServlet?method=showCheckCode&time="+new Date().getTime();
}
</script>
<div class="form-group">
<label for="date" class="col-sm-2 control-label">验证码</label>
<div class="col-sm-3">
<input type="text" class="form-control" id="writeCode" onkeyup="checkCodeMethod(this.value)" >
</div>
<div class="col-sm-2">
<img src="${pageContext.request.contextPath}/UserServlet?method=showCheckCode" id="checkCodeImage" title="点击换一张" onclick="changeCodeImage(this)" />
</div>
<span id="checkCodeSpan"></span>
</div>
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功能二：ajax动态验证验证码
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/**
* 验证验证码
*/
public void checkCode(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取从页面中接收到的验证码参数
String checkCode = req.getParameter("checkCode");
//从session域对象中获取验证码
String sessionCode = (String) req.getSession().getAttribute("checkCode");
//判断验证码是否相同
if (checkCode.equalsIgnoreCase(sessionCode)) {
resp.getWriter().print(true);
}else {
resp.getWriter().print(false);
}
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jsp页面
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<script type="text/javascript">
function changeCodeImage(img){
img.src = "${pageContext.request.contextPath}/UserServlet?method=showCheckCode&time="+new Date().getTime();
}
function checkCodeMethod(code){
$.get("${pageContext.request.contextPath}/UserServlet?method=checkCode",
{ checkCode: code},
function(data){
if (data == 'true') {
document.getElementById("checkCodeSpan").innerHTML = "<font>验证码正确!</font>";
}else {
document.getElementById("checkCodeSpan").innerHTML = "<font>验证码错误!</font>";
}
}
);
}
</script>
<div class="form-group">
<label for="date" class="col-sm-2 control-label">验证码</label>
<div class="col-sm-3">
<input type="text" class="form-control" id="writeCode" onkeyup="checkCodeMethod(this.value)" >
</div>
<div class="col-sm-2">
<img src="${pageContext.request.contextPath}/UserServlet?method=showCheckCode" id="checkCodeImage" title="点击换一张" onclick="changeCodeImage(this)" />
</div>
<span id="checkCodeSpan"></span>
</div>
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感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！
原文链接：http://blog.csdn.net/shuaicihai/article/details/54730590