java实现登录页面的验证码功能

package com.test;

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 javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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

/**
* @see HttpServlet#HttpServlet()
*/
public ValidateCodeServle() {
super();
// TODO Auto-generated constructor stub
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(request, response);
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 响应头信息
response.setHeader("Pragma", "No-Cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expries", 0);

// 随机数生成类
Random random = new Random();

// 定义验证码的位数
int size = 5;

// 定义变量保存生成的验证码
String vCode = "";
char c;
// 产生验证码
for (int i = 0; i < size; i++) {
// 产生一个26以内的随机整数
int number = random.nextInt(26);
// 如果生成的是偶数，则随机生成一个数字
if<
c583
/span> (number % 2 == 0) {
c = (char) ('0' + (char) ((int) (Math.random() * 10)));
// 如果生成的是奇数，则随机生成一个字母
} else {
c = (char) ((char) ((int) (Math.random() * 26)) + 'A');
}
vCode = vCode + c;
}

// 保存生成的5位验证码
request.getSession().setAttribute("vCode", vCode);

// 验证码图片的生成
// 定义图片的宽度和高度
int width = (int) Math.ceil(size * 20);
int height = 30;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// 获取图片的上下文
Graphics gr = image.getGraphics();
// 设定图片背景颜色
gr.setColor(Color.WHITE);
gr.fillRect(0, 0, width, height);
// 设定图片边框
gr.setColor(Color.GRAY);
gr.drawRect(0, 0, width - 1, height - 1);
// 画十条干扰线
for (int i = 0; i < 5; i++) {
int x1 = random.nextInt(width);
int y1 = random.nextInt(height);
int x2 = random.nextInt(width);
int y2 = random.nextInt(height);
gr.setColor(randomColor());
gr.drawLine(x1, y1, x2, y2);
}
// 设置字体，画验证码
gr.setColor(randomColor());
gr.setFont(randomFont());
gr.drawString(vCode, 10, 22);
// 图像生效
gr.dispose();
// 输出到页面
ImageIO.write(image, "JPEG", response.getOutputStream());

}

// 生成随机的颜色
private Color randomColor() {
int red = r.nextInt(150);
int green = r.nextInt(150);
int blue = r.nextInt(150);
return new Color(red, green, blue);
}

private String[] fontNames = { "宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312" };
private Random r = new Random();

// 生成随机的字体
private Font randomFont() {
int index = r.nextInt(fontNames.length);
String fontName = fontNames[index];// 生成随机的字体名称
int style = r.nextInt(4);
int size = r.nextInt(3) + 24; // 生成随机字号, 24 ~ 28
return new Font(fontName, style, size);
}

}