JavaWeb实现验证码

17-02-28 来源：[db:作者]

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JavaWeb实现验证码

创建一个ImageServlet类，这个类实现了输出验证码的功能。具体代码如下：

ImageServlet:

@WebServlet("/ImageServlet")
public class ImageServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public ImageServlet() {
        super();

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("image/jpg;charset=utf-8");

        //在内存中创建一个图片对象，宽度120，高度30
        int width = 120;
        int height = 30;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //获取一个绘制的对象
        Graphics g = image.getGraphics();
        //设置颜色为蓝色
        g.setColor(Color.BLUE);
        //画一个蓝色矩形
        g.drawRect(0, 0, width, height);
        //设置颜色灰色
        g.setColor(Color.GRAY); 
        //给图片进行填充灰色
        g.fillRect(2, 2, width-4, height-4);
        //设置颜色为红色
        g.setColor(Color.RED);
        //设置字体为黑体，大小20，字体样式加粗、斜体
        g.setFont(new Font("黑体", Font.BOLD|Font.ITALIC, 20));

        Random random = new Random();
        int position = 10;
        //随机绘制4个数字
        for (int i = 0; i < 4; i++) {
            String content= Integer.toString(random.nextInt(10));
            //绘制数字
            g.drawString(content,position, 20);
            //排列数字的位置
            position+=30;
        }
        //绘制8条干扰线
        for (int i = 0; i < 8; i++) {
            g.setColor(Color.DARK_GRAY);
            //绘制深灰色的干扰线
            g.drawLine(random.nextInt(width), random.nextInt(height), random.nextInt(width), random.nextInt(height));
        }
        //输出图片
        ImageIO.write(image ,"jpg", response.getOutputStream());
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);
    }

}

在web.xml设置ImageServlet配置

<servlet>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>com.yundoku.ImageServlet</servlet-class>
</servlet>
 
<servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/image</url-pattern>
</servlet-mapping>

image.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
     function changeImage() {
        var img = document.getElementsByTagName("img")[0];
        img.src="/TomcatDemo/image?time="+new Date().getTime();//这个目的是防止缓存不刷新验证码
    } 
</script>
</head>
<body>
    <form>
        <table>
            <tr align="left" height="30">
                <td>用户名：</td>
                <td><input type="text" name="username"/></td>
            </tr >
            <tr align="left" height="30">
                <td>密码：</td>
                <td><input type="password" name="password"/></td>
            </tr>
            <tr align="left" height="30">
                <td>验证码：</td>
                <td><input type="text" name="username"/>&nbsp;&nbsp;<img src="/TomcatDemo/image" onclick="changeImage()"/>&nbsp;<a href="javascript：changeImage()" >看不清，换一张</a></td>
            </tr>
            <tr height="24"><td colspan="2"><input type="submit" value="提交"/></td></tr>
        </table>
    </form>
</body>
</html>

效果如图所示：

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