java-web绘制验证码图片例程
页面html代码：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function changeImage() {
document.getElementById("randomCode").src = "/randomCode?"
+ Math.random();解决点击验证码没有反应问题
}
</script>
</head>
<body>
<form action="/login" method="post">
用户名:<input name="username" type="text"><br /> 密码:<input
name="password" type="password"><br /> 验证码:<input name="code"
type="text"><img alt="" src="/randomCode" id="randomCode"
style="cursor: pointer;" onclick="changeImage()"> ${error}<br />
<input type="submit" value="登录">
</form>
</body>
</html>
java代码：
package test.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang3.StringUtils;
public class LoginServlet extends HttpServlet {
/**
* @see HttpServlet#service(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
String code = request.getParameter("code");
String randomCode = (String) request.getSession().getAttribute(
"randomCode");
if (StringUtils.equalsIgnoreCase(code, randomCode)) {
System.out.println("执行正常的业务逻辑");
} else {
request.setAttribute("error", "验证码出错");
request.getRequestDispatcher("/login.jsp").forward(request,
response);
}
}
}
package test.servlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import java.util.UUID;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class RandomCodeServlet
*/
public class RandomCodeServlet extends HttpServlet {
protected void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String randomCode = (UUID.randomUUID().toString()).substring(0, 4);
request.getSession().setAttribute("randomCode", randomCode);
response.setContentType("image/jpeg"); // 因为向客户端发送的内容是图片. 所以用这种内容类型
int width = 100;
int height = 50;
// 1.创建一个图片对象
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_BGR);
// 2.得到画布
Graphics graphics = image.getGraphics();
// 3.开始在图片上画画
// 3.1 用白色填充. 首先要设置上下文的颜色
graphics.setColor(Color.white);// 设置白色
graphics.fillRect(1, 1, width - 2, height - 2);
// 3.2 用黑色写文字
graphics.setColor(Color.black);
graphics.setFont(new Font("宋体", Font.BOLD, 30));
graphics.drawString(randomCode, width / 6, height / 2 + 5);
// 3.3 画混淆内容
graphics.setColor(Color.red);
for (int i = 0; i < 50; i++) {
graphics.fillOval(new Random().nextInt(width),
new Random().nextInt(height), 3, 3);
}
for (int i = 0; i < 10; i++) {
graphics.setColor(new Color[] { Color.red, Color.blue, Color.GRAY }[new Random()
.nextInt(3)]);
graphics.drawLine(new Random().nextInt(width),
new Random().nextInt(height), new Random().nextInt(width),
new Random().nextInt(height));
}
// 4.关闭画布,释放资源...
graphics.dispose();
// 输出图片
ImageIO.write(image, "JPG", response.getOutputStream());
}
}