JS实现验证码

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ImgServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException {

// 1:声明图片大小

int width = 60;

int height = 25;

// 2:生成内存中的图片

BufferedImage img = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);

// 3:获取画笔

Graphics g = img.getGraphics();

g.setColor(new Color(226, 239, 247));

// 4:画背景

g.fillRect(0, 0, width, height);

// 5:设置字体、大小

g.setFont(new Font("宋体", Font.BOLD, 18));

// 6:生成四个数

String sCode = "";

Random r = new Random();

for (int i = 0; i < 4; i++) {

int a = r.nextInt(10);

// 写出这个数

Color c = new Color(r.nextInt(256), r.nextInt(256),

r.nextInt(256));

g.setColor(c);

g.drawString("" + a, i * 15, 24);

sCode += a;

}

// 放到session中

request.getSession().setAttribute("scode", sCode);

// 7:生效

g.dispose(); // 相当于flush()

// 8:输出图片

response.setContentType("image/jpeg");// 设置输出的类型

OutputStream out = response.getOutputStream();

// 输出

ImageIO.write(img, "JPEG", out);

}

}

public class LoginServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doPost(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException {

// 5:一次性设置所有获取到的参数都是UTF-8

request.setCharacterEncoding("UTF-8");

// 3:设置输出的编码格式和类型

response.setContentType("text/html;charset=UTF-8");

PrintWriter out = response.getWriter();

// 1:获取用户提交的参数的值

String code = request.getParameter("code");

// 从session中获取验证码

String sCode = (String) request.getSession().getAttribute("scode");

// 判断验证码是否正确

if (!code.equals(sCode)) {

out.print("你的验证码错误。。。");

return;

}

}

}

Jsp页面输出：

method="post">