java实现登录页面的验证码功能-蒲公英云

java实现登录页面的验证码功能

我们访问电商网站，登录账号时。都需要验证码的输入。那么在java中，我们是如何实现验证码的呢？这里，我用servelet做个demo。

代码清单：

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 (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);
    }
}